Findings from research carried out in Pakistan have been published in the journal BMJ Quality Improvements.
The idea was first tested in a Lahore hospital using simple pictures of the sun, moon and stars to help patients understand when and how long to take their medication for.
The project has now spread and is currently being rolled out in Canada and doctors hope it will soon be adopted in the UK, where a recent survey estimated that one in five adults is 'functionally illiterate.'
Work by Dr Matthew Clayton and colleagues, working in outpatient clinics in Lahore found that even after counselling, only 12% of illiterate patients understood their prescription when leaving hospital. This left them risking relapses or possible under or overdosing.