What percentage of human blood is made up of red blood cells?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Blood plasma — blood Blood sediment in test tubes, showing plasma (clear fluid), red blood cells (red), and the release of hemoglobin into the surrounding plasma (pink).

The percentage of human blood volume occupied by red blood cells is measured by a diagnostic procedure called a hematocrit. This value varies based on sex and age.21

In healthy adults, the volume of packed red blood cells typically falls within the following ranges:

Men: Approximately 42 to 54 percent2
Women: Approximately 37 to 47 percent2

These values are generally lower in children. An abnormal hematocrit—whether the percentage is too high or too low—can serve as an important clinical indicator of various health conditions, such as anemia or polycythemia.2341