Blood Tests

You and your doctor can learn a great deal about your health by testing a sample of your blood. Blood tests can help…
•  Provide basic information about your health
•  Determine what is "normal" for you, that is,establish a baseline that can be used forcomparison with future test results
•  Detect a medical condition before you have any symptoms
•  Confirm that a medical condition exists
•  Identify the cause of your symptoms
•  Find out if your medicine is working
•  Rule out a disease 

Your test results are usually reported along with a reference range of expected or desired values to help guide your doctor in interpreting them. Reference ranges reflect the numeric values found in healthy people; however, a small number of healthy people (5%) have values that are higher or lower than the ones shown in the reference range. Thus, values higher or lower than those in the reference range might or might not indicate a medical condition.  In addition to the reference range, your doctor will consider other factors when interpreting your test results. These factors include your personal and family medical history, results from a physical exam, and other test results. Your doctor will also think about things that might cause an incorrect test result such as improper sample collection or handling or improper patient preparation.   Therefore, it's important that you talk with your doctor about the meaning of your test results.  The following test descriptions can help you better understand some frequently ordered blood tests so  that discussions with your doctor can be more meaningful.   

Alanine Aminotransferase Blood Test  (ALT Blood Test  )  ALT is an enzyme found mainly in the liver, but it is also present in red blood cells and in the heart. ALT is a good indicator of liver function and liver cell damage. Hepatitis, cirrhosis, alcohol and drug abuse, medications, herbs, and obesity are among the things that can cause high levels of ALT. 

Albumin  Blood Test  Albumin is a type of protein that makes up about two-thirds of the total protein circulating in blood. This important protein keeps water inside the blood vessels. When the albumin level is too low, water can leak out of the blood vessels into other parts of the body and cause swelling. A low level of albumin in the blood can be caused by malnutrition, too much water in the body, liver and kidney ailments, severe injuries such as burns or major bone fractures, and slow bleeding over a long period of time. A high level of albumin may indicate dehydration (not enough water in the body). 

Alkaline Phosphatase Blood Test  (ALP Blood Test  , Alk Phos Blood Test  ) Alkaline phosphatase is an enzyme found in all body tissues, but the most important sites are bone and liver. Blood levels increase when bones are growing; thus children have higher levels than adults do. High levels of ALP can be seen in conditions involving the bone and liver. Certain drugs can also cause abnormal levels. For example, people who use aspirin for a long time and women who use birth control pills can have high alkaline phosphatase levels.

 Aspartate Aminotransferase Blood Test  (AST Blood Test  ) AST is an enzyme found mainly in the heart, liver, and muscles. Thus, high levels of AST in the blood suggest medical conditions that affect the heart, liver, or muscles. For example, chronic alcoholism affects the liver and causes a high AST level. Drug overdose, cirrhosis, congestive heart failure, and muscular dystrophy are among the many other causes of high AST levels. 

Bilirubin Blood Test  , Total Bilirubin is a waste product that is formed when hemoglobin, the oxygen-carrying protein, is broken down in the liver. There are two forms of bilirubin: direct bilirubin and indirect bilirubin. Together, they make up the total bilirubin. Too much bilirubin can cause your skin and the whites of your eyes to appear yellow. This condition is known as jaundice. One cause of jaundice is hemolytic anemia, a condition in which too many red blood cells (the hemoglobin-carrying cells in blood) are destroyed. Liver ailments and blocked bile ducts also cause jaundice. Fasting can cause a slight increase in total bilirubin. 

Bilirubin Blood Test  , Direct This is the soluble form of bilirubin; it can dissolve in water. Normally very little of this form of bilirubin is present in the blood. Thus, even a small increase in the direct bilirubin level can indicate a problem in the liver or bile ducts. 

Blood Urea Nitrogen Blood Test  (BUN Blood Test  ) BUN is a waste product produced when proteins are broken down in the liver. It is excreted by the kidneys. When the kidneys are not working well, the BUN level will rise. Dehydration and blood loss can also cause a high BUN level. A low BUN level might indicate liver ailments, a low protein diet, or too much water intake. 

Bun/Creatinine Ratio Blood Test  This ratio is calculated using the BUN and creatinine test results. The ratio helps the doctor find out if a high BUN level is caused by a kidney problem or by something like blood loss into the gut (intestine).

Calcium Blood Test  Calcium is one of the most important elements in the body. Ninety-nine percent of the calcium in the body is in the bones; the remaining one percent is in body fluids, such as blood. Calcium is very important for the proper functioning of nerves, enzymes, muscles, and blood clotting. High levels can be caused by too much milk and antacid (this is often seen in people with ulcers), too much vitamin D, overactivity of the thyroid or parathyroid gland, and various types of cancer. Low levels can be caused by low albumin or total protein levels, high phosphorus levels, too little vitamin D, and certain medications. Low levels can also be caused by an underactive parathyroid gland and by other medical conditions.  

Carbon Dioxide Blood Test  (CO2 Blood Test  ) CO2 is the waste product of breathing. When you take a breath, oxygen enters your body. Oxygen then binds to hemoglobin in the red blood cells and is carried in the blood to all parts of the body. When the body uses oxygen, CO2 is produced. The CO2 is then carried in the blood back to the lungs. When you breathe out, CO2 is released from your body. CO2 levels help your doctor diagnose different conditions in which the amount of acid or base in the blood is either too high or too low. These include chronic lung conditions, prolonged vomiting, severe diarrhea, hyperventilation, kidney failure, and other medical conditions. 

Chloride Blood Test  (Cl Blood Test  ) Chloride is an electrolyte that plays a role in both acid/base and salt/water balance. Changes in the chloride level are usually associated with changes in the sodium level; when one goes up the other goes down and vice versa. Thus, a small increase or Chloride is an electrolyte that plays a role in both acid/base and salt/water balance. Changes in the chloride level are usually associated with changes in the sodium level; when one goes up the other goes down and vice versa. Thus, a small increase or decrease in the chloride level generally has very little significance. When there is too much or too little acid in the blood, however, chloride is an important clue that helps doctors determine the cause of the acid abnormality. 

Cholesterol Blood Test  , Total Cholesterol is a fat that our bodies need to remain healthy, but too much can clog blood vessels and increase the risk of heart disease. Total blood cholesterol includes LDL ("bad" cholesterol) and HDL ("good" cholesterol). 

Cholesterol Blood Test  , HDL Blood Test  High density lipoprotein (HDL) cholesterol is called the "good" cholesterol because it protects against heart disease. HDL carries cholesterol away from the arteries to the liver. The liver then removes the cholesterol from the body. Thus, when there's more HDL, more cholesterol can be carried away so that it doesn't clog up the arteries and possibly lead to a heart attack. 

Cholesterol/HDL Ratio Blood Test  The total cholesterol and the HDL cholesterol test results are used to calculate the cholesterol/HDL ratio. This ratio provides more information than do the levels of cholesterol and HDL by themselves. The ratio gives doctors a more complete picture of their patient's heart disease risk. The higher this ratio is, the greater the risk of heart disease. 

Cholesterol, LDL Blood Test  Low density lipoprotein (LDL) cholesterol is called the "bad" cholesterol because high levels increase the risk of heart disease. When there is too much LDL, it can build up in the arteries and cause a blockage that results in a heart attack or stroke.

 Creatinine Blood Test  Creatinine is a waste product that is formed when food is converted to energy and when muscles are injured. The amount of creatinine in the blood depends on your sex. Men have higher values than women because they have more muscle mass. The amount of creatinine in the blood also depends on the ability of the kidneys to excrete creatinine. High levels of creatinine often mean that the kidneys are not doing a good job of clearing waste products and toxins from the blood. 

Ferritin Blood Test  Ferritin is a protein that binds to iron when it is stored in the body. Thus, the ferritin test is an indirect measure of the amount of iron that is stored in the body for future use. Low levels might indicate iron deficiency anemia (too little iron). High levels are associated with hemochromatosis (too much iron). 

Gamma-Glutamyltransferase (GGT Blood Test  ) GGT is an enzyme primarily found in the liver. GGT levels can be high when either the liver or the bile ducts are obstructed. Too much alcohol and certain drugs can also cause high levels of GGT. 

Globulin Blood Test  Globulin is a type of protein that makes up about onethird of the total protein circulating in blood. There are about 60 of these globulins, each one different from the other. Globulin helps to fight infection and clot the blood. High globulin levels sometimes occur in people who have an infection or rheumatoid arthritis. Low globulin levels might indicate liver or kidney problems. If your total globulin level is outside the reference range, your doctor might want to measure some of the specific globulins to get more information. 

Glucose Blood Test  Glucose is the chief source of energy for all living organisms and, as such, is very important for a healthy body. However, abnormally high or low blood glucose (blood sugar) levels might be a sign of a medical condition. For example, high glucose levels after 12 hours of fasting is consistent with diabetes. Low blood glucose, on the other hand, might be seen with certain tumors or with liver disorders. A low glucose level might also mean that the blood sample was not handled properly after it was drawn. 

Iron (Fe Blood Test  ) Iron is a metal the body uses to make hemoglobin, the protein that carries oxygen to the cells. Without oxygen, the cells, especially muscle cells in adults and brain cells in children, don't work properly. Too little iron causes anemia. On the other hand, too much iron can injure the heart, pancreas, joints, testicles, ovaries, and other organs. Iron levels are high in people with hemochromatosis, an inherited condition that affects the skin, liver, bones, joints, and pancreas. 

Lactate Dehydrogenase (LD Blood Test  or LDL Blood Test  ) LD is an enzyme found in all tissues in the body. It helps to release energy from glucose. A high LD level can be caused by liver, heart, or lung conditions, anemia, infection, and cancer. Slightly elevated levels are common and rarely indicate medical conditions. 

Magnesium (Mg Blood Test  ) Magnesium is a metal found primarily inside the cells of the body; but, like calcium, the level in blood is important. A low magnesium level in the blood might indicate severe malnutrition, severe diarrhea, alcoholism, or excessive use of diuretics. Low levels are also associated with heart disease. High levels are associated with severe kidney disease. The test is particularly useful for evaluating medical conditions affecting the heart, kidney, and acid/base/water balance. 

Phosphate Blood Test  Phosphate (phosphorus) is found primarily in the bones, but it is also found in the blood. Phosphate is very important for strong, healthy bones and for muscle and nerve function. Very low levels of phosphate in the blood can be caused by starvation or malnutrition and can lead to muscle weakness. Low levels can also be caused by antacids, diuretics, low levels of vitamin D, an overactive parathyroid gland, and certain types of cancer. High levels are usually associated with exercise, dehydration, an underactive parathyroid gland, and kidney disorders. 

Potassium (K Blood Test  ) Potassium is an electrolyte found inside all cells. It helps optimize the amount of water inside the cells and helps in the transmission of nerve impulses. The level of potassium in the blood is very important. Low levels can be caused by use of diuretics, low dietary intake, severe vomiting or diarrhea, certain medications, alcohol abuse, and other medical conditions. A low potassium level can cause muscle weakness and heart problems. People with kidney disorders and those who take too many potassium supplements can have high potassium levels. Some "salt" substitutes contain potassium in place of sodium. Excessive use of these salt substitutes can cause dangerously high levels of potassium in the blood. 

Sodium (Na Blood Test  ) Sodium is an electrolyte that plays an important role in balancing the amount of salt and water in the body. A low level in the blood can be caused by too much water intake, heart failure, or kidney failure caused by fluid retention. A low level can also be caused by loss of sodium in diarrhea, fluid, or vomit. A high level can be caused by intake of too much salt or not enough water. 

T4 (Thyroxine Blood Test  ) T4 is a hormone that controls the rate at which energy is used and released by the body. A low level of T4 (hypothyroidism) can cause tiredness, depression, or weight gain even though your appetite is decreased. A high level of T4 (hyperthyroidism) can cause nervousness, irritability, or weight loss. 

Total Iron Binding Capacity (TIBC Blood Test  ) Iron is transported in the blood bound to a protein called transferrin. Transferrin moves the iron from the iron storage sites to where it is needed in the body. It also transports the iron back to the storage sites when not needed. TIBC is an indirect measurement of transferrin levels. A low TIBC level can be found in patients with malnutrition or too much iron. A high TIBC level is consistent with too little iron. 

Total Protein Blood Test  The total protein test measures the total amount of protein in the blood. Normally, albumin makes up two-thirds of the total protein and globulin makes up the other one-third. When the total protein level is outside the reference range, your doctor might order additional tests to find out if there is a problem with your kidneys or liver. 

Transferrin Percent Saturation Blood Test  This percent is obtained by comparing the iron level to the TIBC level. It is a simple way to compare the amount of iron in the blood to the capacity of the blood to transport iron. The percent saturation is low when there is too little iron and high when there is too much stored iron.

Triglyceride Blood Test  Triglyceride is a type of fat that comes from food, but it is also made in the body. People with high triglyceride levels often have high levels of cholesterol (total, HDL, and/or LDL). As with cholesterol, high triglyceride levels are related to an increased risk of heart disease. People who have diabetes are more likely to have high triglyceride levels. 

TSH Blood Test  Thyroid stimulating hormone (TSH) is a hormone that is produced in the pituitary gland. It signals the thyroid gland to release T4 when blood levels of T4 are low. Doctors use the TSH test to check for thyroid conditions and to be sure people who are taking thyroid medication are getting the right amount.

 Uric Acid Blood Test  Uric acid levels are useful to doctors who suspect their patient has gout. Gout tends to run in families and is a form of arthritis that is more common in men than in women. Diets high in purines (present in sweetbreads, kidney, and liver) might worsen the condition. A number of drugs, particularly diuretics and aspirin, can increase uric acid. Uric acid levels can also be increased during kidney failure, with certain tumors, and as a response to stress and alcohol.