Background: Subsidizing the cost of medicines through insurance schemes increases consumption of medicines and may contribute to irrational use of antibiotics. Objectives: To describe the systemic antibiotics prescriptions patterns and analyze the determinants of their utilization in the National Health insurance Scheme (NHIS).Methods: Established WHO guideline was followed to conduct this cross-sectional retrospective study at University of Nigeria Teaching Hospital, Nigeria. Data were collected from randomly sampled prescription sheets of one year duration. Logistic regression analysis was performed to determine the predictors of antibiotics prescriptions.Results: The results are based on 802 sampled out-patients NHIS prescriptions. Average number of medicines per encounter was 4.0 ± 1.8, whereas 46.9% of antibiotics were prescribed by generic name. Penicillins (most frequently amoxicillin/clavulanate), and nitroimidazole (most frequently metronidazole) were the most commonly prescribed antibiotics with percentage share of 43.3% and 22.2%. Being <5 years old, and taking more than 4 medicines (OR 2.20, 95% CI 1.37-3.55) were the factors associated with the highest risk of antibiotics exposure.Conclusion: There were poly-pharmacy, and non-adherence to generic antibiotic prescriptions. Penicillins (amoxicillin/clavulanate) were the most commonly prescribed antibiotic class. Being < 5 years old, and taking more than 4 medicines were significant predictors of antibiotics exposure.Keywords: Antibiotics; national health insurance scheme; Nigeria; poly-pharmacy; prescription.