OBJECTIVES: To determine whether currently used meropenem dosages in our hospital provide adequate serum concentrations. METHODS: Trough blood samples taken during the first meropenem concentration monitoring were included. For the evaluation of achievement of the pharmacokinetic/pharmacodynamic (PK/PD) target, MIC of the pathogens defined by the European Committee on Antimicrobial Susceptibility testing was selected. RESULTS: Eighty three patients were enrolled. A large variability in meropenem trough serum concentrations was observed (median 34.3 mg/L, range < 1.0-146.1 mg/L). The lowest PK/PD target for susceptible pathogens (100% T > MIC) was achieved in 100% of patients on dialysis and continuous renal replacement therapy (CRRT) and in 91% non-RRT patients. For pathogens with intermediate susceptibility, 100% T > MIC was attained in all patients on CRRT and 96% on dialysis, only 74% non-RRT patients achieved this PK/PD target. Patients on RRT were more likely to achieve the highest PK/PD target 100% T > 5 × MIC, P < 0.05. Higher proportion of patients on RRT would also require meropenem dose reduction if upper limit 100% T > 10 × MIC was chosen, P < 0.05. CONCLUSIONS: Administration of a standard meropenem dose to critically ill patients leads to a large concentration variability. Thus, a personalised dosing regimen is crucial for the achievement of adequate meropenem exposure.