Continuous renal replacement therapy (CRRT) is frequently used in the intensive care setting for the treatment of acute kidney injury. Dosing guidelines for many commonly used antibiotics were established during intermittent dialysis or in studies examining CRRT at lower blood and dialysis flow rates than are used in common practice. Herein we present data demonstrating frequent subtherapeutic levels of vancomycin in a population of patients on CRRT. Nephrology trainees should be educated as to the risks of under-dosing antibiotics in this population.