Blood count , laboratory test that determines the number of red blood cells(Red blood cells) and white blood cellsLeukocytes) in a given volume of blood. The readings vary according to sex, age, physiological status and general health, but the average individual’s blood contains an average of 5,000,000 red cells and 7,000 white cells per cubic millimeter. aThe differential blood count is the percentage of each type of white blood cell per 100 white cells counted; white cells of a normal adult person are about 55% of neutrophils, 30% of lymphocytes, and small percentages of eosinophils, basophils, monocytes. A reduction in the number of red blood cells is usually associated with bAnemia, an increase or decrease in the number of white blood cells can occur with infections, infections, orLeukemia. Blood counts may also include determining the number of platelets, and the volume of red blood cells in the total blood by% (known asHematocrit), sedimentation rate for red blood cells, hemoglobin concentrations of red cells, and average red cell size.