IntroductionSome medicines purchased are not used, resulting in pharmaceutical waste. Finland, among many other countries, is seeking to reduce the amount of pharmaceutical waste, but little information on this is currently available. This study aimed to evaluate the quantity, type, economic value, and reasons for returning pharmaceutical waste from households to community pharmacies in Finland. MethodsCommunity pharmacies (n = 82) quantified and qualified the amount of pharmaceutical waste returned to them over three days in May 2022. The data was collected using an electronic form. The reasons for returning medicines were asked from customers who returned medicines using a paper questionnaire. The data was analyzed for frequencies and percentages. To estimate the economic value, we used the Finnish medicines prices at the end of June 2022. The annual economic value was calculated by means of a pharmacy size-weighted average. The confidence intervals were estimated using the non-parametric bootstrap method. Sensitivity analyses were conducted to examine the reliability of the results. ResultsIn total, 5173 medicines were returned to pharmacies, of which 66 % were prescription medicines. The most common medicines group returned were medicines for nervous system (18 %), respiratory system (16 %), and alimentary tract and metabolism (12 %). The estimated annual economic value of the medicines returned was 81 million euros (CI 95 % M€61–M€103), of which the cost to society was 43 million euros (CI 95 % M€30–M€60). 799 customers responded to the questionnaire (Response rate 81.9 %). The limited shelf life of the medicine after opening (36 %), improvement of the medical condition or symptom (25 %), and the unnecessarily large pack size (22 %) were common reasons for returning. ConclusionA considerable amount of pharmaceutical waste is returned to pharmacies, causing unnecessary costs to both individuals and society, indicating the need to reduce waste. The limited shelf life and large pack sizes of medicines account for a large proportion of causes for household pharmaceutical waste. Reducing pharmaceutical waste requires action from all actors in the pharmaceutical chain.