The blood cells that are biconcave in shape lack nucleus but contain hemoglobin are called erythrocytes or RBC's. These are commonly known as red blood cells. They are formed in the bone marrow and destroyed in the liver and spleen after 120 days.
A normal range in adults is generally considered to be 4.35 to 5.65 million red blood cells per microliter (mcL) of blood for men and 3.92 to 5.13 million red blood cells per mcL of blood for women. In children, the threshold for high red blood cell count varies with age and sex.Dehydration (If the liquid component of the blood (plasma) is decreased, as in dehydration, the red blood cell count increases. This is due to the red blood cells becoming more concentrated.