BACKGROUND Medication histories acquired upon admission are often incomplete. Using a standardized approach warrants more complete medication reconciliation, however, this is too time consuming to be performed. Other strategies guaranteeing complete medication histories should be explored. We developed a limited list of standardized questions and assessed its impact on completeness of medication histories. METHODS This prospective study enrolled adults presenting to a tertiary care emergency department. In the control group, medication histories were conducted by physicians of general internal medicine conform standard care. In the intervention group, the physicians were obliged to use, besides the standard care, the 'limited questions list' for medication history acquisition. The clinical pharmacist re-obtained medication histories of the patients in both groups using a standardized approach. The primary outcome was the impact of the use of a 'limited questions list' on the frequency of drug omissions in medication histories. RESULTS 260 consecutive patients were enrolled: 130 in the intervention group and 130 in the control group. There was a significant reduction of 49.3% in drug omissions in the intervention group. The omission rate per medication history was 1.1 for the control group, which was significantly lower (0.6) in the intervention group. Antithrombotics were most frequently forgotten in the control care group as opposed to dietary supplements in the intervention group. CONCLUSIONS Drug omission rate in medication histories can be significantly reduced if a limited list of simple questions is used during anamnesis. Widespread use of this tool should be considered to be implemented.