Hematocrit refers to the percentage of blood volume occupied by packed red blood cells. This percentage is determined by spinning the blood in a centrifuge. For instance, a hematocrit of 25% indicates that there are 25 milliliters of red blood cells in every 100 milliliters of blood, meaning the red cells account for one-fourth of the total blood volume.Hematocrit levels vary with age and, after puberty, also differ between sexes. The typical hematocrit ranges are as follows:- Newborns: 55-68%- 1 week old: 47-65%- 1 month old: 37-49%- 3 months old: 30-36%- 1 year old: 29-41%- 10 years old: 36-40%- Adult males: 42-54%- Adult females: 38-46%There may be slight variations in these values depending on the laboratory. The term "hematocrit" was introduced in 1903, derived from the Greek words "hemat-" meaning blood and "krites" meaning judge, thus implying an evaluation of blood. The abbreviation for hematocrit is often used in medical contexts, and informally, it is sometimes referred to as the "crit."
