Nearly £200,000 of prescription medication was wasted in Guernsey and Alderney last year, a study has found.
The research, carried out by the Health and Social Services Department, was based on uncollected prescriptions and packets returned to pharmacies.
It is being presented to the Royal Pharmaceutical Society's annual conference next month.
Reasons for the waste were found to be patients not finishing courses and unnecessary repeat prescriptions.
Pharmacist Elmarie Brache conducted the research with help from the Social Security Department's prescribing advisor, Geraldine O'Riordan.
Unused medicines in the Bailiwick are estimated to have cost £186,000 in 2009.
In the UK it has been estimated the NHS loses about £100m every year through unused medicines.