Also known as Complete Blood Count (CBC), blood count is a diagnostic blood test that measures the cellular composition of blood. It measures the number of red blood cells, white blood cells, hematocrit (Hct), and hemoglobin, mean corpuscular volume, platelet count, mean platelet volume, red blood cell distribution, and mean corpuscular hemoglobin concentration. This is a common diagnostic test ordered by doctors to detect various diseases like anemia, infections, and many other blood disorders. Venous blood is drawn from a patient’s arm and is analyzed in the laboratory. By measuring the volume of white blood cell count in blood, presence of certain diseases like autoimmune diseases, liver diseases, bone marrow conditions, are detected. This is deducted when the white blood cell count is less than the normal range. When the white blood cell count is more than the normal range, presence of diseases like, inflammatory diseases, infections, cancer or even stress is suspected. The normal range for adults is 3.5 to 10.5 billion cells per liter. By measuring the red blood cell count, the volume of red blood cells is measured. In case of lower red blood cell count, it can indicate conditions like anemia, lack of nutrition, prolonged infections, blood loss, cancer, hemorrhage, kidney disease, and others. When the red blood cell count is higher than the normal values (Polycythemia), it can indicate conditions like lung diseases, congestive heart failure, kidney diseases, genetic disorders, congenital defects, liver diseases, benign cysts in kidneys, and others. The normal range for red blood cells in adult males is 4.32 to 5.72 billion cells per liter and in females it is 3.9 to 5.03 trillion cells per liter. Hematocrit measures the ratio of the volume of red blood cells to that of the whole blood. The normal range for men is 38.8 to 50% and women is 34.9 to 44.5%. Mean corpuscular volume measures the average volume of a red blood cell. The normal range is 80 to 100 femtoliters. Mean corpuscular hemoglobin measures the average amount of hemoglobin present in an average red blood cell. The normal range is 27 to 32 picograms. Mean corpuscular hemoglobin concentration measures the concentration of hemoglobin in a volume of red blood cells. The normal range is 32 to 36%. The platelet count measures the number of platelets in a given sample of blood. The normal range is 150-450 billion cells per liter. An increase or decrease in the platelet count indicates an underlying disease condition.