The volume of blood in females is generally lower compared to males. On average, adult females have about 4.5 liters of blood, while adult males have about 5.5 liters. This difference is partly due to females typically having a higher proportion of body fat and less lean muscle mass than males, and blood volume correlates more closely with lean body mass. When expressed relative to body weight, females have about 65 ml of blood per kg, and males have about 80 ml per kg. However, when normalized to lean body mass, the blood volume differences between sexes largely disappear. Additionally, during pregnancy, a female's blood volume can increase by roughly 50% to support fetal development.
