Red blood cell (RBC) transfusion, a life-saving intervention, is limited by reduced RBC potency over time. Cold storage at +4 °C for up to 42 days can reduce transfusion efficacy due to alterations termed the "storage lesion." Strategies to mitigate the storage lesion include alkaline additive solutions and supercooled storage to extend storage by reducing metabolic stresses. However, RBC metabolism during supercooled storage in standard or alkaline additives remains unstudied. This study, thus, investigated the impact of storage additives (alkaline E-Sol5 and standard SAGM) and temperatures (+4 °C, -4 °C, -8 °C) on RBC metabolism during 21- and 42-days storage using high-throughput metabolomics. RBCs stored with E-Sol5 showed increased glycolysis and higher ratios of reduced to oxidized glutathione compared to SAGM. Supercooled storage at -4 °C showed markedly lower hemolysis than -8°C, preserved adenylate pools, decreased glucose consumption, and reduced lactate accumulation and pentose phosphate pathway activation. The combination of supercooled storage and E-Sol5 helped to preserve ATP and 2,3-DPG reservoirs, while preventing catabolism and free fatty acid accumulation. While supercooled storage with E-Sol5 offers a promising alternative to standard storage, preserving RBC metabolic and functional quality, further research is necessary to validate and improve on these foundational findings.