Blood donor BMI is associated with increased hemolysis during cold storage of RBCs and with reduced posttransfusion recovery in NSG mice. Leukoreduced RBC units from 18 donors were stored for 6 weeks and tested weekly as described under methods. Hemolysis measurements were evaluated for each BMI group (<25 kg/m2, normal weight, n = 4; 25-29.9 kg/m2, overweight, n = 7; ≥30 kg/m2, obese, n = 7). A, Percent storage hemolysis. B, Percent osmotic hemolysis. C, Percent AAPH-induced oxidative hemolysis. D, Posttransfusion recovery of 6-week-old leukoreduced RBC transfused into NSG mice. N = 14 of which n = 3 for BMI <25 kg/m2, n = 6 for BMI 25-29.9 kg/m2, and n = 5 for BMI ≥30 kg/m2. Data are represented as mean ± SEM. Asterisks denote significance (P < 0.05, repeated measures two-way ANOVA with Bonferroni’s multicomparison test) of differences between nonobese (<25 or 25-29.9 kg/m2) and obese samples (A); <25 vs ≥30 kg/m2 (B); and between 25-29.9 and BMI ≥30 kg/m2 (D)