A national survey has found 60 per cent of people keep unwanted and expired medicines in the house.

Australians are risking their health by hoarding unwanted, out-of-date and unused medicines in their homes, new research shows.

A national survey of more than 4,000 people conducted by Griffith University researchers found 60 per cent of the population keep unwanted and used medicines in the house "just in case they needed them again".

One-third of these medicines had expired, according to the survey published in CSIRO journal Australian Health Review.

Other common reasons for not throwing medicines away included not wanting to waste money, not knowing how to dispose of them, intending to give them to family and friends, or forgetting the medicines were there.

Keeping used and expired medicines at home can be risky, the researchers warned on Wednesday.

Keeping medicines to use for re-occurring conditions, like migraines, is appropriate, but keeping antibiotics to use for a different infection can lead to treatment failure if those antibiotics do not target the new infection.

Another risk from using antibiotics incorrectly could result in bacteria changing to become more resistant to treatment, the researchers said.

"Stockpiling of medicines in households and using out-of-date medicines could also contribute to public health risks, such as accidental ingestion, poisoning and delayed treatment if medicines are ineffective," they wrote.

Disposing of them in the garbage or down the toilet also carries severe environmental risks, they added.

The survey also found more than 80 per cent of people had not heard of the Federal Government's Return Unwanted Medicines Scheme.