Hematology is the study of blood and its disorders. Hematologists, board-certified internists, look specifically at blood components such as blood count, and blood and bone marrow cells. Hematological tests can help diagnose anemia, hemophilia, blood-clotting disorders, and leukemia. Blood samples are most often collected in lavender top tubes.

Complete Blood Count (CBC)

The CBC is one of the most common blood tests. It is often done as part of a routine checkup.

The CBC can help detect blood diseases and disorders, such as anemia, infections, clotting problems, blood cancers, and immune system disorders. This test measures many different parts of your blood, as discussed in the following paragraphs.

Red Blood Cells

Red blood cells carry oxygen from your lungs to the rest of your body. Abnormal red blood cell levels may be a sign of anemia, dehydration (too little fluid in the body), bleeding, or another disorder.

White Blood Cells

White blood cells are part of your immune system, which fights infections and diseases. Abnormal white blood cell levels may be a sign of infection, blood cancer, or an immune system disorder.

A CBC measures the overall number of white blood cells in your blood. A CBC with differential looks at the amounts of different types of white blood cells in your blood.

Platelets

Platelets (PLATE-lets) are blood cell fragments that help your blood clot. They stick together to seal cuts or breaks on blood vessel walls and stop bleeding.

Abnormal platelet levels may be a sign of a bleeding disorder (not enough clotting) or a thrombotic disorder (too much clotting).

Hemoglobin

Hemoglobin (HEE-muh-glow-bin) is an iron-rich protein in red blood cells that carries oxygen. Abnormal hemoglobin levels may be a sign of anemia, sickle cell anemia, thalassemia (thal-a-SE-me-ah), or other blood disorders.

If you have diabetes, excess glucose in your blood can attach to hemoglobin and raise the level of hemoglobin A1c.

Hematocrit

Hematocrit (hee-MAT-oh-crit) is a measure of how much space red blood cells take up in your blood. A high hematocrit level might mean you’re dehydrated. A low hematocrit level might mean you have anemia. Abnormal hematocrit levels also may be a sign of a blood or bone marrow disorder.

Mean Corpuscular Volume

Mean corpuscular (kor-PUS-kyu-lar) volume (MCV) is a measure of the average size of your red blood cells. Abnormal MCV levels may be a sign of anemia or thalassemia.

Blood Chemistry Tests/Basic Metabolic Panel

The basic metabolic panel (BMP) is a group of tests that measures different chemicals in the blood. These tests usually are done on the fluid (plasma) part of blood. The tests can give doctors information about your muscles (including the heart), bones, and organs, such as the kidneys and liver.

The BMP includes blood glucose, calcium, and electrolyte tests, as well as blood tests that measure kidney function. Some of these tests require you to fast (not eat any food) before the test, and others don’t. Your doctor will tell you how to prepare for the test(s) you’re having.

Blood Glucose

Glucose is a type of sugar that the body uses for energy. Abnormal glucose levels in your blood may be a sign of diabetes.

For some blood glucose tests, you have to fast before your blood is drawn. Other blood glucose tests are done after a meal or at any time with no preparation.

Calcium

Calcium is an important mineral in the body. Abnormal calcium levels in the blood may be a sign of kidney problems, bone disease, thyroid disease, cancer, malnutrition, or another disorder.

Electrolytes

Electrolytes are minerals that help maintain fluid levels and acid-base balance in the body. They include sodium, potassium, bicarbonate, and chloride.

Abnormal electrolyte levels may be a sign of dehydration, kidney disease, liver disease, heart failure, high blood pressure, or other disorders.

Kidneys

Blood tests for kidney function measure levels of blood urea nitrogen (BUN) and creatinine (kre-AT-ih-neen). Both of these are waste products that the kidneys filter out of the body. Abnormal BUN and creatinine levels may be signs of a kidney disease or disorder.

Blood Enzyme Tests

Enzymes are chemicals that help control chemical reactions in your body. There are many blood enzyme tests. This section focuses on blood enzyme tests used to check for heart attack. These include troponin and creatine (KRE-ah-teen) kinase (CK) tests.

Troponin

Troponin is a muscle protein that helps your muscles contract. When muscle or heart cells are injured, troponin leaks out, and its levels in your blood rise.

For example, blood levels of troponin rise when you have a heart attack. For this reason, doctors often order troponin tests when patients have chest pain or other heart attack signs and symptoms.

Creatine Kinase

A blood product called CK-MB is released when the heart muscle is damaged. High levels of CK-MB in the blood can mean that you’ve had a heart attack.

Blood Tests to Assess Heart Disease Risk

A lipoprotein panel is a blood test that can help show whether you’re at risk for coronary heart disease (CHD). This test looks at substances in your blood that carry cholesterol.

A lipoprotein panel gives information about:

• Total cholesterol.
• LDL (“bad”) cholesterol. This is the main source of cholesterol buildup and blockages in the arteries. (For more information about blockages in the arteries, go to the Diseases and Conditions Index Atherosclerosis article.)
• HDL (“good”) cholesterol. This type of cholesterol helps decrease blockages in the arteries.
• Triglycerides. Triglycerides are a type of fat in your blood.

A lipoprotein panel measures the levels of LDL and HDL cholesterol and triglycerides in your blood. Abnormal cholesterol and triglyceride levels may be signs of increased risk for CHD.

Most people will need to fast for 9 to 12 hours before a lipoprotein panel