BACKGROUND: Extracorporeal membrane oxygenation (ECMO) can alter the pharmacokinetics of diverse antimicrobials, posing challenges in achieving therapeutic drug levels. Some literature suggests that teicoplanin may require higher dosing in ECMO patients, however the respective evidence is scarce. The aim of this study was to assess teicoplanin trough levels in critically patients on ECMO support and to compare patients with and without additional continuous renal replacement therapy (CRRT). We conducted a retrospective study at the Intensive Care Unit (ICU) of the University Hospital Zurich, Switzerland. Teicoplanin trough levels and doses were analyzed in critically ill patients during ECMO support by means of a non-parametric local estimated polynomial regression. Outcomes included the proportion of patients with insufficient or toxic teicoplanin trough levels, dosage adjustments, and differences in teicoplanin trough levels between patients with and without additional CRRT during ECMO support. RESULTS: After screening 172 patients receiving teicoplanin therapy during their ICU stay from 1.1.2020 to 19.07.2023, a total of 23 adult patients were included. The proportion of patients with insufficient teicoplanin levels was notably higher during ECMO support compared to patients with toxic levels (78.3% vs. 13% of patients, respectively). Teicoplanin dosages mostly were increased during the first few days of ECMO treatment. Concomitant CRRT led to a further increase in the proportion of patients with insufficient levels. CONCLUSIONS: Teicoplanin trough levels using standard dosing tend to be low in patients on ECMO support, especially in the early days of therapy. Higher doses than the standard regimen are often necessary to achieve therapeutic levels, particularly in patients receiving additional CRRT.