BLOOD AND URINE TESTING
Complete Blood Count
A complete blood count (CBC) gives important information about the kinds and numbers of cells in the blood, especially red blood cells , white blood cells , and platelets . A CBC helps your doctor check any symptoms, such as weakness, fatigue, or bruising, you may have. A CBC also helps him or her diagnose conditions, such as anemia , infection, and many other disorders.
A CBC test usually includes:
• White blood cell (WBC, leukocyte) count. White blood cells protect the body against infection. If an infection develops, white blood cells attack and destroy the bacteria, virus, or other organism causing it. White blood cells are bigger than red blood cells but fewer in number. When a person has a bacterial infection, the number of white cells rises very quickly. The number of white blood cells is sometimes used to find an infection or to see how the body is dealing with cancer treatment.
• White blood cell types (WBC differential). The major types of white blood cells are neutrophils , lymphocytes, monocytes, eosinophils, and basophils. Immature neutrophils, called band neutrophils, are also part of this test. Each type of cell plays a different role in protecting the body. The numbers of each one of these types of white blood cells give important information about the immune system . Too many or too few of the different types of white blood cells can help find an infection, an allergic or toxic reaction to medicines or chemicals, and many conditions, such as leukemia .
• Red blood cell (RBC) count. Red blood cells carry oxygen from the lungs to the rest of the body. They also carry carbon dioxide back to the lungs so it can be exhaled. If the RBC count is low (anemia), the body may not be getting the oxygen it needs. If the count is too high (a condition called polycythemia), there is a chance that the red blood cells will clump together and block tiny blood vessels (capillaries). This also makes it hard for your red blood cells to carry oxygen.
• Hematocrit (HCT, packed cell volume, PCV). This test measures the amount of space (volume) red blood cells take up in the blood. The value is given as a percentage of red blood cells in a volume of blood. For example, a hematocrit of 38 means that 38% of the blood's volume is made of red blood cells. Hematocrit and hemoglobin values are the two major tests that show if anemia or polycythemia is present.
• Hemoglobin (Hgb). The hemoglobin molecule fills up the red blood cells. It carries oxygen and gives the blood cell its red color. The hemoglobin test measures the amount of hemoglobin in blood and is a good measure of the blood's ability to carry oxygen throughout the body.
• Red blood cell indices. There are three red blood cell indices: mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC). They are measured by a machine, and their values come from other measurements in a CBC. The MCV shows the size of the red blood cells. The MCH value is the amount of hemoglobin in an average red blood cell. The MCHC measures the concentration of hemoglobin in an average red blood cell. These numbers help in the diagnosis of different types of anemia. Red cell distribution width (RDW) can also be measured which shows if the cells are all the same or different sizes or shapes.
• Platelet (thrombocyte) count. Platelets (thrombocytes) are the smallest type of blood cell. They are important in blood clotting. When bleeding occurs, the platelets swell, clump together, and form a sticky plug that helps stop the bleeding. If there are too few platelets, uncontrolled bleeding may be a problem. If there are too many platelets, there is a chance of a blood clot forming in a blood vessel. Also, platelets may be involved in hardening of the arteries ( atherosclerosis ).
• Mean platelet volume (MPV). Mean platelet volume measures the average amount (volume) of platelets. Mean platelet volume is used along with platelet count to diagnose some diseases. If the platelet count is normal, the mean platelet volume can still be too high or too low.
Your doctor may order a blood smear test to be done at the same time as a CBC but it is not part of the regular CBC test. In this test, a drop of blood is spread (smeared) on a slide and stained with a special dye. The slide is looked at under a microscope. The number, size, and shape of red blood cells, white blood cells, and platelets are recorded. Blood cells with different shapes or sizes can help diagnose many blood diseases, such as leukemia, malaria , or sickle cell disease .
A complete blood count may be done to:
• Find the cause of symptoms such as fatigue, weakness, fever, bruising, or weight loss.
• Check for anemia.
• See how much blood has been lost if there is bleeding.
• Diagnose polycythemia .
• Check for an infection.
• Diagnose diseases of the blood, such as leukemia.
• Check how the body is dealing with some types of drug or radiation treatment.
• Check how abnormal bleeding is affecting the blood cells and counts.
• Screen for high and low values before a surgery.
• See if there are too many or too few of certain types of cells. This may help find other conditions, such as too many eosinophils may mean an allergy or asthma is present.
Electrolyte Panal
An electrolyte panel is a blood test that measures the levels of electrolytes and carbon dioxide in your blood.
Electrolytes are minerals, such as sodium and potassium, that are found in the body. They keep your body's fluids in balance and help keep your body working normally, including your heart rhythm, muscle contraction, and brain function.
Carbon dioxide (CO2) is also measured in this test. CO2 is a waste product made when the body breaks down food for energy ( metabolism ). It takes the form of bicarbonate in the blood, so this part of the test is sometimes called a bicarbonate test. Bicarbonate helps your blood stay at the right pH .
Your doctor may order an electrolyte panel as part of a regular health examination. Your doctor may use this test to check on or diagnose a medical condition. Your doctor can also use an electrolyte panel to see if any medicines that you take have changed your electrolyte levels. An electrolyte panel measures the blood levels of carbon dioxide, chloride, potassium, and sodium.
• Carbon Dioxide (Bicarbonate)
• Chloride
• Potassium
• Sodium
Carbon dioxide (CO2) is a gaseous waste product from metabolism . The blood carries carbon dioxide to your lungs, where it is exhaled. More than 90% of it in your blood exists in the form of bicarbonate (HCO3). The rest of it is either dissolved carbon dioxide gas (CO2) or carbonic acid (H2CO3). Your kidneys and lungs balance the levels of carbon dioxide, bicarbonate, and carbonic acid in the blood.
This test measures the level of bicarbonate in a sample of blood from a vein. Bicarbonate is a chemical that acts as a buffer. It keeps the pH of blood from becoming too acidic or too basic.
Bicarbonate is not usually tested by itself. The test may be done on a blood sample taken from a vein as part of a panel of tests that looks at other electrolytes . These may include items such as sodium, potassium, and chloride. It can also be done as part of an arterial blood gas (ABG) test. For this blood gas study, the blood sample comes from an artery. A carbon dioxide test helps find and checks conditions that affect blood bicarbonate levels. These include many kidney diseases, some lung diseases, and metabolic problems.
A chloride test measures the level of chloride in your blood or urine. Chloride is one of the most important electrolytes in the blood. It helps keep the amount of fluid inside and outside of your cells in balance. It also helps maintain proper blood volume, blood pressure, and pH of your body fluids. Tests for sodium, potassium, and bicarbonate are usually done at the same time as a blood test for chloride.
Most of the chloride in your body comes from the salt (sodium chloride) you eat. Chloride is absorbed by your intestines when you digest food. Extra chloride leaves your body in your urine.
Sometimes a test for chloride can be done on a sample of all your urine collected over a 24-hour period (called a 24-hour urine sample) to find out how much chloride is leaving your body in your urine.
Chloride can also be measured in skin sweat to test for cystic fibrosis .
A test for chloride may be done to:
• Check your chloride level if you are having symptoms such as muscle twitching or spasms, breathing problems, weakness, or confusion.
• Find out whether you have kidney or adrenal gland problems.
• Help find the cause for high blood pH. A condition called metabolic alkalosis can be caused by a loss of acid from your body (for example, from a loss of electrolytes through prolonged vomiting or diarrhea). You may also have metabolic alkalosis if your body loses too much sodium or you eat too much baking soda (sodium bicarbonate).
A potassium test checks how much potassium is in the blood. Potassium is both an electrolyte and a mineral. It helps keep the water (the amount of fluid inside and outside the body's cells) and electrolyte balance of the body. Potassium is also important in how nerves and muscles work.
Potassium levels often change with sodium levels. When sodium levels go up, potassium levels go down, and when sodium levels go down, potassium levels go up. Potassium levels are also affected by a hormone called aldosterone, which is made by the adrenal glands .
Potassium levels can be affected by how the kidneys are working, the blood pH , the amount of potassium you eat, the hormone levels in your body, severe vomiting, and taking certain medicines, such as diuretics and potassium supplements. Certain cancer treatments that destroy cancer cells can also make potassium levels high.
Many foods are rich in potassium, including bananas, orange juice, spinach, and potatoes. A balanced diet has enough potassium for the body's needs. But if your potassium levels get low, it can take some time for your body to start holding on to potassium. In the meantime, potassium is still passed in the urine, so you may end up with very low levels of potassium in your body, which can be dangerous.
A potassium level that is too high or too low can be serious. Abnormal potassium levels may cause symptoms such as muscle cramps or weakness, nausea, diarrhea, frequent urination, dehydration , low blood pressure, confusion, irritability, paralysis, and changes in heart rhythm.
Other electrolytes, such as sodium, calcium, chloride, magnesium, and phosphate, may be checked in a blood sample at the same time as a blood test for potassium.
A blood test to check potassium is done to:
• Check levels in people being treated with medicines such as diuretics and for people having kidney dialysis .
• Check to see whether treatment for too low or too high potassium levels is working.
• Check people with high blood pressure who may have a problem with their kidneys or adrenal glands.
• Check the effects of extra nutrition ( total parenteral nutrition [TPN] ) on potassium levels.
• Check to see whether certain cancer treatments are causing too many cells to be destroyed (cell lysis). Cell lysis syndrome causes very high levels of some electrolytes, including potassium.
A sodium test checks how much sodium is in the blood. Sodium is both an electrolyte and mineral. It helps keep the water (the amount of fluid inside and outside the body's cells) and electrolyte balance of the body. Sodium is also important in how nerves and muscles work.
Most of the sodium in the body (about 85%) is found in blood and lymph fluid. Sodium levels in the body are partly controlled by a hormone called aldosterone, which is made by the adrenal glands . Aldosterone levels tell the kidneys when to hold sodium in the body instead of passing it in the urine. Small amounts of sodium are also lost through the skin when you sweat.
Most foods have sodium naturally in them or as an ingredient in cooking. Sodium is found in table salt as sodium chloride or in baking soda as sodium bicarbonate. Many medicines and other products also have sodium in them, including laxatives, aspirin, mouthwash, and toothpaste.
Low sodium levels are uncommon and are most often caused by heart failure, malnutrition, and diarrhea.
Other electrolytes, such as potassium, calcium, chloride, magnesium, and phosphate, may be checked in a blood sample at the same time as a blood test for sodium.
A blood test to check sodium levels is done to:
• Check the water and electrolyte balance of the body.
• Find the cause of symptoms from low or high levels of sodium.
• Check the progress of diseases of the kidneys or adrenal glands.
Blood Urea Nitrogen (BUN)
A blood urea nitrogen (BUN) test measures the amount of nitrogen in your blood that comes from the waste product urea. Urea is made when protein is broken down in your body. Urea is made in the liver and passed out of your body in the urine.
A BUN test is done to see how well your kidneys are working. If your kidneys are not able to remove urea from the blood normally, your BUN level rises. Heart failure , dehydration , or a diet high in protein can also make your BUN level higher. Liver disease or damage can lower your BUN level. A low BUN level can occur normally in the second or third trimester of pregnancy.
Blood creatinine level
The blood creatinine level shows how well your kidneys are working. A high level may mean your kidneys are not working as they should. The amount of creatinine in the blood depends partly on the amount of muscle tissue you have. Men generally have higher creatinine levels than women. Creatinine tests measure the level of the waste product creatinine (say "kree-AT-uh-neen") in your blood and urine. These tests tell how well your kidneys are working. Another substance, creatine (say "KREE-uh-teen"), is formed when food is changed into energy through a process called metabolism . Creatine is broken down into creatinine. Your kidneys take creatinine out of your blood and pass it out of your body in urine. If your kidneys are damaged and can't work as they should, the amount of creatinine in your urine goes down while its level in your blood goes up.
Blood urea nitrogen to creatinine ratio (BUN:creatinine)
A BUN test may be done with a blood creatinine test. The level of creatinine in your blood also tells how well your kidneys are working-a high creatinine level may mean your kidneys are not working properly. Blood urea nitrogen (BUN) and creatinine tests can be used together to find the BUN-to-creatinine ratio (BUN:creatinine). A BUN-to-creatinine ratio can help your doctor check for problems, such as dehydration, that may cause abnormal BUN and creatinine levels.
A blood urea nitrogen (BUN) test is done to:
• See if your kidneys are working normally.
• See if your kidney disease is getting worse.
• See if treatment of your kidney disease is working.
• Check for severe dehydration. Dehydration generally causes BUN levels to rise more than creatinine levels. This causes a high BUN-to-creatinine ratio. Kidney disease or blockage of the flow of urine from your kidney causes both BUN and creatinine levels to go up.
Creatinine tests measure the level of the waste product creatinine (say "kree-AT-uh-neen") in your blood and urine. These tests tell how well your kidneys are working.
Another substance, creatine (say "KREE-uh-teen"), is formed when food is changed into energy through a process called metabolism . Creatine is broken down into creatinine. Your kidneys take creatinine out of your blood and pass it out of your body in urine.
If your kidneys are damaged and can't work as they should, the amount of creatinine in your urine goes down while its level in your blood goes up.
Three types of tests can be done.
Glucose
A blood glucose test measures the amount of a type of sugar, called glucose, in your blood. Glucose comes from carbohydrate foods . It is the main source of energy used by the body. Insulin is a hormone that helps your body's cells use the glucose. Insulin is produced in the pancreas and released into the blood when the amount of glucose in the blood rises.
Normally, your blood glucose levels increase slightly after you eat. This increase causes your pancreas to release insulin so that your blood glucose levels do not get too high. Blood glucose levels that remain high over time can damage your eyes, kidneys, nerves, and blood vessels.
There are several different types of blood glucose tests.
• Fasting blood sugar (FBS) measures blood glucose after you have not eaten for at least 8 hours. It is often the first test done to check for prediabetes and diabetes .
For a fasting blood sugar test, do not eat or drink anything other than water for at least 8 hours before the blood sample is taken.
If you have diabetes, you may be asked to wait until you have had your blood tested before taking your morning dose of insulin or diabetes medicine. You may have a random blood sugar test instead, which will not require an 8-hour fast.
• 2-hour postprandial blood sugar measures blood glucose exactly 2 hours after you start eating a meal. This is not a test used to diagnose diabetes. This test is used to see if someone with diabetes is taking the right amount of insulin with meals.
• Random blood sugar (RBS) measures blood glucose regardless of when you last ate. Several random measurements may be taken throughout the day. Random testing is useful because glucose levels in healthy people do not vary widely throughout the day. Blood glucose levels that vary widely may mean a problem. This test is also called a casual blood glucose test.
• Oral glucose tolerance test is used to diagnose prediabetes and diabetes. An oral glucose tolerance test is a series of blood glucose measurements taken after you drink a sweet liquid that contains glucose. This test is commonly used to diagnose diabetes that occurs during pregnancy ( gestational diabetes ). Women who had high blood sugar levels during pregnancy may have oral glucose tolerance tests after pregnancy.
• Hemoglobin A1c, or glycohemoglobin, measures how much sugar (glucose) is stuck to red blood cells. This test can be used to diagnose diabetes. It also shows how well your diabetes has been controlled in the past 2 to 3 months and whether your diabetes medicine needs to be changed. The result of your A1c test can be used to estimate your average blood sugar level. This is called your estimated average glucose, or eAG.
A C-peptide test can be done when diabetes has just been found and it is not clear whether type 1 diabetes or type 2 diabetes is present. A person whose pancreas does not make any insulin (type 1 diabetes) has a low level of insulin and C-peptide. A person with type 2 diabetes can have a normal or high level of C-peptide.
A C-peptide test can also help find the cause of low blood sugar ( hypoglycemia ), such as excessive use of medicine to treat diabetes or a noncancerous growth (tumor) in the pancreas (insulinoma). Because man-made (synthetic) insulin does not have C-peptide, a person with a low blood sugar level from taking too much insulin will have a low C-peptide level but a high level of insulin. An insulinoma causes the pancreas to release too much insulin, which causes blood sugar levels to drop (hypoglycemia). A person with an insulinoma will have a high level of C-peptide in the blood when they have a high level of insulin.
To make a diagnosis of type 2 diabetes, your doctor will use the American Diabetes Association's criteria.
Blood glucose tests are done to:
• Check for prediabetes and diabetes.
• Monitor treatment of diabetes.
• Check for diabetes that occurs during pregnancy (gestational diabetes).
• Determine if an abnormally low blood sugar level ( hypoglycemia ) is present. A test to measure blood levels of insulin and a protein called C-peptide may be done along with a blood glucose test to determine the cause of hypoglycemia because insulin and C-peptide are linked when first made by the pancreas. Insulin helps the body use and control the amount of sugar (glucose) in the blood. Insulin allows glucose to enter body cells where it is used for energy. The level of C-peptide in the blood can show how much insulin is being made by the pancreas . C-peptide does not affect the blood sugar level in the body.
Thyroid Tests
Thyroid hormone tests are blood tests that check how well the thyroid gland is working. The thyroid gland makes hormones that regulate the way the body uses energy.
The thyroid gland is a butterfly-shaped gland that lies in front of your windpipe (trachea), just below your voice box (larynx). The thyroid gland uses iodine from food to make two thyroid hormones : thyroxine (T4) and triiodothyronine (T3). The thyroid gland stores these thyroid hormones and releases them as they are needed.
Thyroid hormones are needed for normal development of the brain, especially during the first 3 years of life. Intellectual disability may occur if a baby's thyroid gland does not produce enough thyroid hormone (congenital hypothyroidism ). Older children also need thyroid hormones to grow and develop normally, and adults need the hormones to regulate the way the body uses energy ( metabolism ).
Thyroid hormone blood tests include:
• Total thyroxine (T4). Most of the thyroxine (T4) in the blood is bound to a protein called thyroxine-binding globulin. Less than 1% of the T4 is free. A total T4 blood test measures both free and bound thyroxine. Free thyroxine affects tissue function in the body, but bound thyroxine does not.
• Free thyroxine (FTI or FT4). Free thyroxine (T4) can be measured directly (FT4) or calculated as the free thyroxine index (FTI). The FTI tells how much free T4 is present compared to bound T4. The FTI can help tell if abnormal amounts of T4 are present because of abnormal amounts of thyroxine-binding globulin.
• Triiodothyronine (T3). Most of the T3 in the blood is attached to thyroxine-binding globulin. Less than 1% of the T3 is unattached. A T3 blood test measures both bound and free triiodothyronine. T3 has a greater effect on the way the body uses energy than T4, even though T3 is normally present in smaller amounts than T4.
Thyroid hormone tests are done to:
• Find out what is causing an abnormal thyroid-stimulating hormone (TSH) test. For more information, see the topic Thyroid-Stimulating Hormone (TSH). This is the most common reason for thyroid hormone tests.
• Check how well treatment of thyroid disease is working. The total thyroxine (T4), free thyroxine (FT4), and free thyroxine index (FTI) values are often used to keep track of treatment for hyperthyroidism .
• Screen newborns to find out if the thyroid gland function is normal. A condition called congenital hypothyroidism can prevent normal growth and development and cause other severe problems, such as intellectual disability, if it is not treated soon after birth.
Many medicines may change the results of this test. Be sure to tell your doctor about all the nonprescription and prescription medicines you take. If you are taking thyroid medicines, tell your doctor when you took your last dose. Your doctor may instruct you to stop taking thyroid medicines temporarily before having this test.
A thyroid-stimulating hormone (TSH) blood test is used to check for thyroid gland problems. TSH is produced when the hypothalamus releases a substance called thyrotropin-releasing hormone (TRH). TRH then triggers the pituitary gland to release TSH.
TSH causes the thyroid gland to make two hormones: triiodothyronine (T3) and thyroxine (T4). T3 and T4 help control your body's metabolism .
Triiodothyronine (T3) and thyroxine (T4) are needed for normal growth of the brain, especially during the first 3 years of life. A baby whose thyroid gland does not make enough thyroid hormone (congenital hypothyroidism) may, in severe cases, be mentally retarded. Older children also need thyroid hormones to grow and develop normally.
This test may be done at the same time as tests to measure T3 and T4.
A test for thyroid-stimulating hormone (TSH) is done to:
• Find out whether the thyroid gland is working properly.
• An underactive thyroid gland ( hypothyroidism ) can cause symptoms such as weight gain, tiredness, dry skin, constipation, a feeling of being too cold, or frequent menstrual periods.
• An overactive thyroid ( hyperthyroidism ) can cause symptoms such as weight loss, rapid heart rate, nervousness, diarrhea, a feeling of being too hot, or irregular menstrual periods.
• Find the cause of an underactive thyroid gland (hypothyroidism). TSH levels can help determine whether hypothyroidism is due to a damaged thyroid gland or some other cause (such as a problem with the pituitary gland or the hypothalamus).
• Keep track of treatment with thyroid replacement medicine for people who have hypothyroidism.
• Keep track of thyroid gland function in people who are being treated for hyperthyroidism. This treatment may include antithyroid medicine, surgery, or radiation therapy.
• Double-check the diagnosis of an underactive thyroid gland in a newborn (congenital hypothyroidism).
Tell your doctor if you have had any tests in which you were given radioactive materials or had X-rays that used iodine dye within the last 4 to 6 weeks. Your test results may not be correct if you have had iodine contrast material before having a thyroid-stimulating hormone (TSH) test.
Testosterone
A testosterone test checks the level of this male hormone (androgen) in the blood. Testosterone affects sexual features and development. In men, it is made in large amounts by the testicles . In both men and women, testosterone is made in small amounts by the adrenal glands , and in women, by the ovaries .
The pituitary gland controls the level of testosterone in the body. When the testosterone level is low, the pituitary gland releases a hormone called luteinizing hormone (LH) . This hormone tells the testicles to make more testosterone.
Before puberty , the testosterone level in boys is normally low. Testosterone increases during puberty. This causes boys to develop a deeper voice, get bigger muscles, make sperm , and get facial and body hair. The level of testosterone is the highest around age 40, then gradually becomes less in older men.
In women, the ovaries account for half of the testosterone in the body. Women have a much smaller amount of testosterone in their bodies compared to men. But testosterone plays an important role throughout the body in both men and women. It affects the brain, bone and muscle mass, fat distribution, the vascular system, energy levels, genital tissues, and sexual functioning.
Most of the testosterone in the blood is bound to a protein called sex hormone binding globulin (SHBG). Testosterone that is not bound ("free" testosterone) may be checked if a man or a woman is having sexual problems. Free testosterone also may be tested for a person who has a condition that can change SHBG levels, such as hyperthyroidism or some types of kidney diseases.
Total testosterone levels vary throughout the day. They are usually highest in the morning and lowest in the evening.
A testosterone test is done to:
• See why a man is having problems in fathering a child (infertility). A low amount of testosterone can lead to low sperm counts.
• Check a man's sexual problems. Having a low level of testosterone may lower a man's sex drive or not allow him to have an erection (erectile dysfunction).
• See whether a high level of testosterone is causing a boy younger than age 10 to have early signs of puberty.
• Find out why a woman is developing male features, such as excessive facial and body hair (hirsutism) and a deep voice.
• Find out why a woman is having irregular menstrual periods.
• See if testosterone-lowering medicines are working in a man with advanced prostate cancer .
• Find the cause of osteoporosis in a man.
You do not need to do anything before you have this test. Your doctor may want you to do a morning blood test because testosterone levels are highest between 7 a.m. and 9 a.m.
Estrogen Tests
An estrogen test measures the level of the most important estrogen hormones in a blood or urine sample. It measures estradiol, estriol, and estrone.
• Estradiol is the most common type of estrogen measured for non-pregnant women. The amount of estradiol in a woman's blood varies throughout her menstrual cycle . After menopause , it drops to a very low but constant level.
• Estriol levels are most often measured only during pregnancy. Estriol is produced in large amounts by the placenta . This is the tissue that links the fetus to the mother. Estriol can be found as early as the 9th week of pregnancy. The levels keep rising until delivery. Estriol can also be measured in urine.
• Estrone may be measured in women who have gone through menopause. It's done to find out their estrogen levels. It also may be measured in men or women who might have cancer of the ovaries, testicles, or adrenal glands.
Both men and women make estrogen hormones. Estrogens are responsible for female sexual development and function, such as breast development and the menstrual cycle. In women, estrogens are made mainly in the ovaries and in the placenta during pregnancy. Small amounts are also made by the adrenal glands. In men, small amounts of estrogens are made by the adrenal glands and testicles.
Small amounts of estrone are made throughout the body in most tissues, especially fat and muscle. This is the major source of estrogen in women who have gone through menopause. A test for estrogen is done to:
• Check for estrogen-producing tumors of the ovaries in girls before menstruation starts and in women after menopause.
• Explain abnormal sexual traits in men, such as enlarged breasts (gynecomastia). This test can also help find out if there are estrogen-producing tumors growing in the testicles.
Iron Studies
An iron test checks the amount of iron in the blood to see how well iron is metabolized in the body. Iron (Fe) is a mineral needed for hemoglobin, the protein in red blood cells that carries oxygen. Iron is also needed for energy, good muscle and organ function.
About 70% of the body's iron is bound to hemoglobin in red blood cells . The rest is bound to other proteins (transferrin in blood or ferritin in bone marrow) or stored in other body tissues. When red blood cells die, their iron is released and carried by transferrin to the bone marrow and to other organs such as the liver and spleen. In the bone marrow, iron is stored and used as needed to make new red blood cells.
The source of all the body's iron is food, such as liver and other meat, eggs, fish, and leafy green vegetables. The body needs more iron at times of growth (such as during adolescence), for pregnancy, during breastfeeding, or at times when there are low levels of iron in the body (such as after bleeding).
Healthy adult men get enough iron from the food they eat. Men have enough reserves of iron in their bodies to last for several years, even if they take in no new iron. Men rarely develop an iron deficiency because of their diets. But women can lose large amounts of iron because of menstrual bleeding, during pregnancy, or while breastfeeding. So women are more likely than men to develop an iron deficiency and may need to take an iron supplement. Iron deficiency in men and in women past menopause is often from abnormal bleeding, often in the gastrointestinal tract, such as from stomach ulcers or colon cancer .
The iron test checks the:
• Amount of iron bound to transferrin in the blood (serum).
• Amount of iron needed to bind to all of the transferrin. This value is called the total iron-binding capacity (TIBC).
• Percentage of transferrin with iron bound to them. This value is called transferrin saturation.
A test for iron is done to:
• Check for iron deficiency anemia .
• Check for a condition called hemochromatosis .
• Check nutritional status.
• Check to see if iron and nutritional treatment is working.
Do not take iron supplements for 12 hours before having an iron test.
Iron levels change throughout the day so it is best to do iron tests in the morning, when iron levels are highest.
Cortisol
A cortisol test is done to measure the level of the hormone cortisol in the blood. The cortisol level may show problems with the adrenal glands or pituitary gland . Cortisol is made by the adrenal glands . Cortisol levels go up when the pituitary gland releases another hormone called adrenocorticotropic hormone (ACTH).
Cortisol has many functions. It helps the body use sugar (glucose) and fat for energy ( metabolism ), and it helps the body manage stress. Cortisol levels can be affected by many conditions, such as physical or emotional stress, strenuous activity, infection, or injury.
Normally, cortisol levels rise during the early morning hours and are highest about 7 a.m. They drop very low in the evening and during the early phase of sleep. But if you sleep during the day and are up at night, this pattern may be reversed. If you do not have this daily change (diurnal rhythm) in cortisol levels, you may have overactive adrenal glands. This condition is called Cushing's syndrome .
The timing of the cortisol test is very important because of the way cortisol levels vary throughout a day. If your doctor thinks you might make too much cortisol, the test will probably be done late in the day. If your doctor thinks you may not be making enough, a test is usually done in the morning. A cortisol test is done to find problems of the pituitary gland or adrenal glands, such as making too much or too little hormones.
You may be asked to avoid strenuous physical activity the day before a cortisol test. You may also be asked to lie down and relax for 30 minutes before the blood test.
Many medicines may change the results of this test. Some medicines, such as steroids, can affect cortisol levels for some time even after you stop taking the medicine. Be sure to tell your doctor about all the nonprescription and prescription medicines you take.
C-Reactive Protein
A C-reactive protein (CRP) test is a blood test that measures the amount of a protein called C-reactive protein in your blood. C-reactive protein measures general levels of inflammation in your body. High levels of CRP are caused by infections and many long-term diseases. But a CRP test cannot show where the inflammation is located or what is causing it. Other tests are needed to find the cause and location of the inflammation. A C-reactive protein (CRP) test is done to:
• Identify and keep track of infections and diseases that cause inflammation, such as:
• Cancer of the lymph nodes ( lymphoma ).
• Diseases of the immune system, such as lupus .
• Painful swelling of the blood vessels in the head and neck ( giant cell arteritis ).
• Painful swelling of the tissues that line the joints ( rheumatoid arthritis ).
• Swelling and bleeding of the intestines ( inflammatory bowel disease ).
• Infection of a bone ( osteomyelitis ).
• Check to see how well treatment is working, such as treatment for cancer or for an infection. CRP levels go up quickly and then become normal quickly if you are responding to treatment measures.
There is no special preparation for a C-reactive protein (CRP) test. You might be asked to not eat or drink for a few hours before the test.
Liver Function Tests (LFTs)
A liver (hepatic) function panel is a blood test to check how well the liver is working. This test measures the blood levels of total protein , albumin , bilirubin , and liver enzymes . High or low levels may mean that liver damage or disease is present.
The liver serves several important functions in the body, including changing nutrients into energy for the body and breaking down toxic substances.
Your doctor may order a liver function panel if you have symptoms of liver disease. These symptoms include fever, vomiting, abdominal pain, yellowing of your eyes or skin ( jaundice ), dark yellow urine, and feeling very tired. This blood test also may be done if you have recently been exposed to a hepatitis virus or are taking a medicine that may cause liver damage.
To learn more, see:
• Total Protein.
• Albumin.
• Bilirubin (total and direct).
• Alkaline Phosphatase (ALP).
• Aspartate Aminotransferase (AST).
• Alanine Aminotransferase (ALT).
A total serum protein test measures the total amount of protein in the blood. It also measures the amounts of two major groups of proteins in the blood: albumin and globulin.
• Albumin is made mainly in the liver. It helps keep the blood from leaking out of blood vessels. Albumin also helps carry some medicines and other substances through the blood and is important for tissue growth and healing.
• Globulin is made up of different proteins called alpha, beta, and gamma types. Some globulins are made by the liver, while others are made by the immune system . Certain globulins bind with hemoglobin . Other globulins transport metals, such as iron, in the blood and help fight infection. Serum globulin can be separated into several subgroups by serum protein electrophoresis. To learn more, see the topic Serum Protein Electrophoresis.
A test for total serum protein reports separate values for total protein, albumin, and globulin. Some types of globulin (such as alpha-1 globulin) also may be measured.
Albumin is tested to:
• Check how well the liver and kidneys are working.
• Find out if your diet contains enough protein.
• Help determine the cause of swelling of the ankles ( edema ) or abdomen ( ascites ) or of fluid collection in the lungs that may cause shortness of breath ( pulmonary edema ).
Globulin is tested to:
• Determine your chances of developing an infection.
• See if you have a blood disease, such as multiple myeloma or macroglobulinemia .
A bilirubin test measures the amount of bilirubin in a blood sample. Bilirubin is a brownish yellow substance found in bile . It is produced when the liver breaks down old red blood cells. Bilirubin is then removed from the body through the stool (feces) and gives stool its normal color.
Bilirubin circulates in the bloodstream in two forms:
• Indirect (or unconjugated) bilirubin. This form of bilirubin does not dissolve in water (it is insoluble). Indirect bilirubin travels through the bloodstream to the liver, where it is changed into a soluble form (direct or conjugated).
• Direct (or conjugated) bilirubin. Direct bilirubin dissolves in water (it is soluble) and is made by the liver from indirect bilirubin.
Total bilirubin and direct bilirubin levels are measured directly in the blood, whereas indirect bilirubin levels are derived from the total and direct bilirubin measurements.
When bilirubin levels are high, the skin and whites of the eyes may appear yellow (jaundice). Jaundice may be caused by liver disease ( hepatitis ), blood disorders ( hemolytic anemia ), or blockage of the tubes (bile ducts) that allow bile to pass from the liver to the small intestine .
Mild jaundice in newborns usually does not cause problems. But too much bilirubin (hyperbilirubinemia) in a newborn baby can cause brain damage ( kernicterus ) and other serious problems. So some babies who develop jaundice may need treatment to lower their bilirubin levels.
The bilirubin test is used to:
• Check liver function and watch for signs of liver disease, such as hepatitis or cirrhosis , or the effects of medicines that can damage the liver.
• Find out if something is blocking the bile ducts. This may occur if gallstones , tumors of the pancreas, or other conditions are present.
• Diagnose conditions that cause increased destruction of red blood cells , such as hemolytic anemia or hemolytic disease of the newborn .
• Help make decisions about whether newborn babies with neonatal jaundice need treatment. These babies may need treatment with special lights, called phototherapy. In rare cases, blood transfusions may be needed.
Alkaline Phosphatase (ALP)
An alkaline phosphatase (ALP) test measures the amount of the enzyme ALP in the blood. ALP is made mostly in the liver and in bone with some made in the intestines and kidneys . It also is made by the placenta of a pregnant woman.
The liver makes more ALP than the other organs or the bones. Some conditions cause large amounts of ALP in the blood. These conditions include rapid bone growth (during puberty), bone disease (such as Paget's disease or cancer that has spread to the bones), a disease that affects how much calcium is in the blood ( hyperparathyroidism ), vitamin D deficiency, or damaged liver cells.
If the ALP level is high, more tests may be done to find the cause. The amounts of different types of ALP in the blood may be measured and used to determine whether a high level is from the liver or bones. This is called an alkaline phosphatase isoenzymes test. A test for alkaline phosphatase (ALP) is done to:
• Check for liver disease or damage to the liver. Symptoms of liver disease can include jaundice , belly pain, nausea, and vomiting. An ALP test may also be used to check the liver when medicines that can damage the liver are taken.
• Check bone problems (sometimes found on X-rays), such as rickets , bone tumors, Paget's disease, or too much of the hormone that controls bone growth ( parathyroid hormone ). The ALP level can be used to check how well treatment for Paget's disease or a vitamin D deficiency is working.
Aspartate Aminotransferase (AST)
An aspartate aminotransferase (AST) test measures the amount of this enzyme in the blood. AST is normally found in red blood cells , liver , heart, muscle tissue, pancreas , and kidneys. AST formerly was called serum glutamic oxaloacetic transaminase (SGOT).
Low levels of AST are normally found in the blood. When body tissue or an organ such as the heart or liver is diseased or damaged, additional AST is released into the bloodstream. The amount of AST in the blood is directly related to the extent of the tissue damage. After severe damage, AST levels rise in 6 to 10 hours and remain high for about 4 days.
The AST test may be done at the same time as a test for alanine aminotransferase, or ALT. The ratio of AST to ALT sometimes can help determine whether the liver or another organ has been damaged. Both ALT and AST levels can test for liver damage. An aspartate aminotransferase (AST) test is done to:
• Check for liver damage.
• Help identify liver disease, such as hepatitis . Liver disease may produce symptoms such as pain in the upper abdomen, nausea, vomiting, and sometimes jaundice .
• Check on the success of treatment for liver disease.
• Find out whether jaundice was caused by a blood disorder or liver disease.
• Keep track of the effects of medicines that can damage the liver.
Alanine Aminotransferase (ALT)
An alanine aminotransferase (ALT) test measures the amount of this enzyme in the blood. ALT is found mainly in the liver, but also in smaller amounts in the kidneys , heart, muscles, and pancreas . ALT was formerly called serum glutamic pyruvic transaminase (SGPT).
ALT is measured to see if the liver is damaged or diseased. Low levels of ALT are normally found in the blood. But when the liver is damaged or diseased, it releases ALT into the bloodstream, which makes ALT levels go up. Most increases in ALT levels are caused by liver damage.
The ALT test is often done along with other tests that check for liver damage, including aspartate aminotransferase (AST), alkaline phosphatase, lactate dehydrogenase (LDH), and bilirubin. Both ALT and AST levels are reliable tests for liver damage. The alanine aminotransferase (ALT) test is done to:
• Identify liver disease, especially cirrhosis and hepatitis caused by alcohol, drugs, or viruses.
• Help check for liver damage.
• Find out whether jaundice was caused by a blood disorder or liver disease.
• Keep track of the effects of medicines that can damage the liver.
Prostate-Specific Antigen (PSA)
A prostate-specific antigen (PSA) test measures the amount of prostate-specific antigen in the blood. PSA is released into a man's blood by his prostate gland . Healthy men have low amounts of PSA in the blood. The amount of PSA in the blood normally increases as a man's prostate enlarges with age. PSA may increase because of inflammation of the prostate gland ( prostatitis ) or prostate cancer . An injury, a digital rectal exam, or sexual activity (ejaculation) may also briefly raise PSA levels.
A vitamin B12 test measures the amount of vitamin B12 in the blood. The body needs this B vitamin to make blood cells and to maintain a healthy nervous system .
Vitamin B12 is found in animal products such as meat, shellfish, milk, cheese, and eggs. Most people who eat animal products are not likely to develop vitamin B12 deficiency anemia unless their bodies can't absorb it from food. Strict vegetarians (vegans) who do not eat animal products and babies of mothers who are strict vegetarians are at increased risk for developing anemia and should take a supplement containing vitamin B12. Vitamin B12 is stored in the liver for a year or more, which reduces a person's risk of anemia.
Vitamin B12 is usually measured at the same time as a folic acid test, because a lack of either one or both can lead to a form of anemia called megaloblastic anemia . Lack of vitamin B12 also affects the nervous system.
A vitamin B12 test is used to:
• Check for vitamin B12 deficiency anemia. There are several risk factors for this anemia, such as those who have had stomach or intestinal surgery, small intestine problems, or people with a family history of this anemia.
• Diagnose the cause of certain types of anemia, such as megaloblastic anemia.
• Help find the cause of dementia or other nervous system symptoms, such as tingling or numbness of the arms or legs (peripheral neuropathy).
• See if vitamin B12 deficiency anemia is present after a person has been diagnosed with atrophic gastritis .
Do not eat or drink (other than water) for 10 to 12 hours before the test.
Urine Test
A urine test checks different components of urine, a waste product made by the kidneys . A regular urine test may be done to help find the cause of symptoms. The test can give information about your health and problems you may have.
The kidneys take out waste material, minerals, fluids, and other substances from the blood to be passed in the urine. Urine has hundreds of different body wastes. What you eat and drink, how much you exercise, and how well your kidneys work can affect what is in your urine.
More than 100 different tests can be done on urine. A regular urinalysis often includes the following tests:
• Color. Many things affect urine color, including fluid balance, diet, medicines, and diseases. How dark or light the color is tells you how much water is in it. Vitamin B supplements can turn urine bright yellow. Some medicines, blackberries, beets, rhubarb, or blood in the urine can turn urine red-brown.
• Clarity. Urine is normally clear. Bacteria, blood, sperm, crystals, or mucus can make urine look cloudy.
• Odor. Urine does not smell very strong, but it has a slightly "nutty" odor. Some diseases cause a change in the odor of urine. For example, an infection with E. coli bacteria can cause a bad odor, while diabetes or starvation can cause a sweet, fruity odor.
• Specific gravity. This checks the amount of substances in the urine. It also shows how well the kidneys balance the amount of water in urine. The higher the specific gravity, the more solid material is in the urine. When you drink a lot of fluid, your kidneys make urine with a high amount of water in it, which has a low specific gravity. When you do not drink fluids, your kidneys make urine with a small amount of water in it, which has a high specific gravity.
• pH. The pH is a measure of how acidic or alkaline (basic) the urine is. A urine pH of 4 is strongly acidic, 7 is neutral (neither acidic nor alkaline), and 9 is strongly alkaline. Sometimes the pH of urine is affected by certain treatments. For example, your doctor may instruct you how to keep your urine either acidic or alkaline to prevent some types of kidney stones from forming.
• Protein. Protein normally isn't found in the urine. Fever, hard exercise, pregnancy, and some diseases, especially kidney disease, may cause protein to be in the urine.
• Glucose. Glucose is the type of sugar found in blood. Normally there is very little or no glucose in urine. When the blood sugar level is very high, as in uncontrolled diabetes, the sugar spills over into the urine. Glucose can also be found in urine when the kidneys are damaged or diseased.
• Nitrites. Bacteria that cause a urinary tract infection (UTI) make an enzyme that changes urinary nitrates to nitrites. Nitrites in urine show a UTI is present.
• Leukocyte esterase (WBC esterase). Leukocyte esterase shows leukocytes ( white blood cells [WBCs] ) in the urine. WBCs in the urine may mean a UTI is present.
• Ketones. When fat is broken down for energy, the body makes substances called ketones (or ketone bodies). These are passed in the urine. Large amounts of ketones in the urine may mean a very serious condition, diabetic ketoacidosis , is present. A diet low in sugars and starches (carbohydrates), starvation, or severe vomiting may also cause ketones to be in the urine.
• Microscopic analysis. In this test, urine is spun in a special machine (centrifuge) so the solid materials (sediment) settle at the bottom. The sediment is spread on a slide and looked at under a microscope. Things that may be seen on the slide include:
• Red or white blood cells. Blood cells aren't found in urine normally. Inflammation, disease, or injury to the kidneys, ureters, bladder, or urethra can cause blood in urine. Strenuous exercise, such as running a marathon, can also cause blood in the urine. White blood cells may be a sign of infection or kidney disease.
• Casts. Some types of kidney disease can cause plugs of material (called casts) to form in tiny tubes in the kidneys. The casts then get flushed out in the urine. Casts can be made of red or white blood cells, waxy or fatty substances, or protein. The type of cast in the urine can help show what type of kidney disease may be present.
• Crystals. Healthy people often have only a few crystals in their urine. A large number of crystals, or certain types of crystals, may mean kidney stones are present or there is a problem with how the body is using food ( metabolism ).
• Bacteria, yeast cells, or parasites. There are no bacteria, yeast cells, or parasites in urine normally. If these are present, it can mean you have an infection.
• Squamous cells. The presence of squamous cells may mean that the sample is not as pure as it needs to be. These cells do not mean there is a medical problem, but your doctor may ask that you give another urine sample.
A urine test may be done:
• To check for a disease or infection of the urinary tract . Symptoms of a urine infection may include colored or bad-smelling urine, pain when urinating, finding it hard to urinate, flank pain, blood in the urine (hematuria), or fever.
• To check the treatment of conditions such as diabetes, kidney stones, a urinary tract infection (UTI), high blood pressure ( hypertension ), or some kidney or liver diseases.
• As part of a regular physical examination.
Magnesium
A magnesium test checks the level of magnesium in the blood. Magnesium is an important electrolyte needed for proper muscle, nerve, and enzyme function. It also helps the body use energy and is needed to move other electrolytes (potassium and sodium) into and out of cells. Most of the magnesium in the body is found in the bones and inside the cells. Only a tiny amount of magnesium is normally present in the blood. Tests for other electrolytes, such as calcium, potassium, sodium, and phosphorus, may be done along with a test for magnesium. A test for magnesium is done to:
• Find a cause for nerve and muscle problems, such as muscle twitches, irritability, and muscle weakness.
• Find the cause of symptoms such as low blood pressure, nausea, vomiting, diarrhea, dizziness, muscle weakness, and slurred speech.
• Monitor kidney function.
• Find the cause of heart problems or trouble breathing, especially in people who have kidney disease.
• Find the cause of a low calcium or potassium level that is not improving with treatment.
• Look for changes in magnesium levels caused by medicines, such as diuretics
• See if people who have heart problems need extra magnesium. Low magnesium levels can increase the chances of life-threatening heart rhythm problems.
• Measure levels when magnesium is being given for medical treatment.
Many medicines may change the results of this test. Be sure to tell your doctor about all the nonprescription and prescription medicines you take. Do not take medicines containing magnesium for at least 3 days before this test. This includes antacids that contain magnesium, laxatives (such as milk of magnesia or Epsom salts), magnesium supplements, and some diuretics .
Folate
Folate is a form of B vitamin that occurs naturally in many foods. Folic acid is the man-made form of folate that is added to processed foods or vitamin and mineral supplements. Folate is needed in the human body for production of red blood cells.
A lack (deficiency) of folate in the human body can be caused by certain diseases, by taking certain medications, or by not getting enough folate in your diet. Folate deficiency can lead to decreased red blood cells, or anemia. Folate deficiency can also cause high levels of a certain amino acid in the blood, a condition called hyperhomocysteinemia.
Zinc
Zinc is an essential element involved in a myriad of enzyme systems including wound healing, immune function, and fetal development. In order to repair micro tears that can occur as a result of strenuous exercise, serious athletes may require higher amounts of vitamins and minerals including zinc. Zinc is essential to keeping the immune system strong. For athletes, this is especially important, since being sidelined with a viral infection, or other illness, can force one to miss valuable workout time. Zinc deficiency can be problematic as plasma testosterone is also regulated in part by zinc. Therefore, a zinc deficiency may adversely affect this hormone, causing muscular mass and strength to suffer.