BACKGROUND: Hemolysis, variably defined in mechanical circulatory support (MCS), is understudied in percutaneous left ventricular assist devices. We characterize hemolytic sequelae of Impella 5.5-supported patients in the largest series to date. METHODS: All Impella 5.5 patients at our center from 2020 to 2023 were identified (n = 169) and retrospectively reviewed. Patients with a plasma free hemoglobin (PfHb) recorded (and not previously elevated) were included (n = 123). The top (high hemolysis [HH], n = 26) and bottom (low hemolysis [LH], n = 25) quintiles were categorized based on PfHb levels. Analysis between groups identified factors associated with hemolysis. RESULTS: HH patients had higher admission SCAI stages (p = 0.008), more Impella 5.5 days (23.5 v 10.0, p = 0.002), more additional MCS (16/26 [61.5%] v 6/25 [24.0%], p = 0.015), and more transfusions of packed red blood cells (12.5 v 4.0, p = 0.002), fresh frozen plasma (2.5 v 0.0, p = 0.033), and platelets (3.0 v 0.0, p = 0.002). Logistic regression identified additional MCS (OR 10.82, p = 0.004) and more Impella days (OR 1.13 p = 0.006) as hemolysis risk factors. Eleven (44%) LH and 19/26 (73%) HH patients died, with no significant differences between postoperative complications. Compared with those who died, HH survivors had fewer platelet transfusions (2.0 vs. 5.0, p = 0.01) and less PfHb elevation days (3.0 v 6.0, p = 0.007). CONCLUSIONS: Hemolysis in this high-risk cohort has a poor prognosis. HH patients spent more days on Impella 5.5, needed more MCS, and required more blood product transfusions.