AimsAccurate documentation of medication administration time is imperative for many therapeutic decisions, including dosing of intravenous antimicrobials. The objectives were to determine (1) the discrepancy between actual and documented administration times for antimicrobial infusions and (2) whether day of the week, time of day, nurse‐to‐patient ratio and drug impacted accuracy of documented administration times.MethodsPatient and dosing data were collected (June–August 2019) for 55 in‐patients receiving antimicrobial infusions. “Documented” and “actual” administration times (n = 660) extracted from electronic medication management systems and smart infusion pumps, respectively, were compared. Influence of the day (weekday/weekend), time of day (day/evening/night), nurse‐to‐patient ratio (high 1:1/low 1:5) and drug were examined. Monte Carlo simulation was used to predict the impact on dose adjustments for vancomycin using the observed administration time discrepancies compared to the actual administration time.ResultsThe median discrepancy between actual and documented administration times was 16 min (range, 2–293 min), with discrepancies greater than 60 minutes in 7.7% of administrations. Overall, discrepancies (median [range]) were similar on weekends (17 [2–293] min) and weekdays (16 [2–188] min), and for high (16 [2–157] min) and low nurse‐to‐patient ratio wards (16 [2–293] min). Discrepancies were smallest for night administrations (P < .05), and antimicrobials with shorter half‐lives (P < .0001). The observed discrepancies in vancomycin administration time resulted in a different dose recommendation in 58% of cases (30% higher, 28% lower).ConclusionsOverall, there were discrepancies between actual and documented antimicrobial infusion administration times. For vancomycin, these discrepancies in administration time were predicted to result in inappropriate dose recommendations.