When you visit your doctor, you may be asked to give a blood sample for a series of tests that evaluate your health. The hematological values obtained from these tests can give your doctor important information about various components of your blood.
One of the most common tests is a complete blood count (CBC). This test measures the amount of various types of cells in your blood, such as white blood cells (leukocytes), red blood cells (erythrocytes), and platelets (thrombocytes). The results can aid in diagnosis of a variety of diseases and medical conditions.
White blood cells are an important part of your immune system and help your body fight infections. They are the largest type cells in your blood. The white blood cell count (WBC) is expressed as a number per cubic millimeter, and the normal range is between 4,000 and 12,000 cells/mm3. Higher levels may indicate the presence of infection or possibly malignancy, and low levels can relate to chemotherapy treatments.
Red blood cells are the most plentiful cells in the blood and carry oxygen to all parts of the body. They are smaller than white blood cells, but larger than platelets. The red blood cell count (RBC) is also expressed as a number per cubic millimeter and the normal range varies by gender. Normal range for men is between 4.3 and 5.9 million cells/mm3 and for women between 3.5 and 5.5 million cells/mm3.
Hemoglobin is the molecule in red blood cells that actually attaches to oxygen and gives blood its red color. Hemoglobin (Hb) is expressed as weight per deciliter. The normal range for men is between 13.5 and 17.5 grams/deciliter and for women between 12 and 16 grams/deciliter. Low results on RBC or Hb can indicate anemia, and high results can be an indicator of hypoxia, a low level of oxygen in the blood.
Platelets are the smallest components of blood. Platelets are a part of the blood clotting system that helps to prevent bleeding. The platelet count is expressed as a number per cubic millimeter. The normal range is between 150,000 and 400,000/mm3. Low platelet count can reflect bleeding over an extended period and a high count can relate to a severe inflammation.
Other measurements are included in the complete blood count such as hematocrit, a ratio of red blood cells to total blood volume, and mean corpuscular hemoglobin concentration, the average concentration of hemoglobin in a specific volume of red blood cells. CBC tests are often used to get baseline values for general health status. Some medications can affect blood counts and routine testing may be used to monitor changes caused by those medications.
None of these numbers is a final diagnosis by itself. Blood test results are evaluated by health care professionals in conjunction with medical symptoms and other types of testing. Healthy blood is essential to overall health, and these hematological measures provide important information about the constituents of your blood.