This review summarises the effect of common medication on sleep patterns. Evaluation of current medication status is an important part of the assessment in case of complaints of disturbed sleep. Medication may affect sleep continuity and sleep architecture directly via effects on wake or sleep promoting neurotransmitter systems and indirectly via beneficial therapeutic effects or unwanted side effects. It is important for clinicians to be aware of potentially sleep disturbing effects of prescribed medication, especially in case of polypharmacy, and to adjust treatment accordingly to avoid disrupted sleep patterns and the resulting impairment of daytime functioning.