Understanding Blood Counts

Counting and examining blood cells are very important in the diagnosis of blood cell diseases. Blood has several different types of cells in it: Red blood cells pick up oxygen as blood passes through the lungs and release it to the cells in the body. White blood cells help fight bacteria and viruses. Platelets are the cells that form a plug in response to a cut or wound. The platelets aggregate and plug up the site of bleeding.

Normal blood counts fall within the range that has been established by testing healthy men and women of all ages. The approximate normal ranges of blood cell counts for healthy adults are as follows:

Red blood cell (RBC) count: 4.5 to 6.0 million red cells per microliter of blood in men, 4.0 to 5.0 million red cells per microliter of blood in women

White blood cell (WBC) count: 4.5 to 11 thousand white cells per microliter of blood

Platelet count: 150 to 450 thousand platelets per microliter of blood

Hematocrit is the percent of the blood that is composed of red cells:
42% to 50% is normal in men
36% to 45% is normal in women

Hemoglobin is the compound in the red blood cell that carries oxygen:
14 to 17 grams per 100 milliliters of blood is normal for men
12 to 15 grams per 100 milliliters of blood is normal for women

White cell differential count, sometimes referred to as a "diff," measures the proportion of the total white cell count that is composed of one of the five principal white cell types. The observer can also tell if the white cells in the blood are normal in appearance. The five types of normal white cells that are counted are neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Blood contains about 60% neutrophils, 30% lymphocytes, 5% monocytes, 4% eosinophils and <1% basophils.