Determinants and reference values for blood volume and total hemoglobin mass in women and men

Blood volume (BV) is an important clinical parameter and is usually reported per kg of body mass (BM). When fat mass is elevated, this underestimates BV/BM. One aim was to study if differences in BV/BM related to sex, age, and fitness would decrease if normalized to lean body mass (LBM). The analysis included 263 women and 319 men (age: 10-93 years, body mass index: 14-41 kg/m² ) and 107 athletes who underwent assessment of BV and hemoglobin mass (Hb_mass ), body composition, and cardiorespiratory fitness. BV/BM was 25% lower (70.3 ± 11.3 and 80.3 ± 10.8 mL/kg^BM ) in women than men, respectively, whereas BV/LBM was 6% higher in women (110.9 ± 12.5 and 105.3 ± 11.2 mL/kg^LBM ). Hb_mass /BM was 34% lower (8.9 ± 1.4 and 11.5 ± 11.2 g/kg^BM ) in women than in men, respectively, but only 6% lower (14.0 ± 1.5 and 14.9 ± 1.5 g/kg^LBM )/LBM. Age did not affect BV. Athlete's BV/BM was 17.2% higher than non-athletes, but decreased to only 2.5% when normalized to LBM. Of the variables analyzed, LBM was the strongest predictor for BV (R²  = .72, p < .001) and Hb_mass (R²  = .81, p < .001). These data may only be valid for BV/Hb_mass when assessed by CO re-breathing. Hb_mass /LBM could be considered a valuable clinical matrix in medical care aiming to normalize blood homeostasis.