Blood Volume in Men vs. Women: Similar When Adjusted for Body Size

Total blood volume (TBV) is ~70 mL/kg in adults. Men average 5–6 L (70–75 mL/kg); women 4–5 L (65–70 mL/kg). The absolute difference (~1 L) is primarily due to larger body size and muscle mass in men, not gender per se.

Determinants

• Body weight and composition (lean mass > fat mass).
• Height, age, fitness level.
• Pregnancy: ↑ 30–50% (1.5 L) by term.

Clinical Relevance

• Transfusion triggers, pharmacokinetics, hemodynamic monitoring use weight-based estimates, not sex.
• Blood donation: 500 mL (~10% TBV) safe for ≥50 kg donors (both sexes).

No intrinsic 1-L gender gap after size adjustment. Volume status assessed clinically and via labs, not sex-based assumptions.