What percentage of body weight is made up of blood?

Blood typically accounts for approximately 7-8% of an individual's total body weight. This percentage can vary slightly based on factors such as body composition, age, and sex. The 8% figure represents a common average used in medical contexts and education, reflecting how significant blood is in terms of mass relative to the entire body.

Understanding the composition of body weight, including the contribution of blood, is crucial for health professionals, particularly in fields like phlebotomy where blood volume and its components play an essential role in patient care and diagnostics. Knowing that blood makes up about 8% of body weight can guide technicians in estimating blood volume and understanding its impact on various medical conditions and treatments.