Genetic factors contributing to l-carnitine levels in 13 091 human RBCs after storage for 42 days. (A) Unsupervised clustering of 13 091 index donors based on RBC metabolism at day 42 identified a subset of donors with significantly higher levels of l-carnitine compared to the rest of the population. (B) l-carnitine showed a skewed distribution across the population. (C) Line plots display the impact of donor age, sex, BMI, and ethnicity on end-of-storage l-carnitine levels in 13 091 blood units. (D-H) Breakdown of donor distributions based on additive solution, sex, age, BMI, and ethnicity for the donors with the highest and lowest end-of-storage RBC l-carnitine levels (n = 500 per group; y-axes show % of total donor in the high vs low subgroup).