Most people with diabetes wear the wrong size of shoe - a mistake which could cost them a leg, say experts.
A badly fitted shoe can have terrible consequences
A Dundee University study of 100 people found only 37 had well-fitting shoes.
If they are too narrow, tight or loose, they can cause ulcers, which can be slow to heal, leading to infections and even amputation.
The study, in the International Journal of Clinical Practice, has prompted calls for the shoe industry to provide better sizes for diabetics.
The number of people with diabetes in the UK is rising, and one of the problems caused by the condition is decline of nerve sensation in the toes and feet.
This can mean that small injuries such as blisters and ulcers go unnoticed, and, coupled with slow healing, this increases the risk of a serious infection.
Another effect is that diabetic people may choose shoes which are too tight - because the increased pressure makes them "feel" like the right size.
Dr Graham Leese, who the led the study, measured the feet of 100 diabetic patients, and found that 63% of them were wearing the wrong size shoes, mostly taking the wrong width fitting.
He said: "We also discovered that almost a third of the patients said they took a different shoe size to the one they were actually wearing. "This isn't helped by the fact that shoe sizes vary from make to make."
Diabetics with nerve problems in their feet and legs are urged by doctors to make daily checks looking for small cuts and scrapes which could cause problems.
Only 29% of those checked by Dr Leese did this, and 22% never checked their feet.
Andrea Parnes, a podiatrist from the University of Ulster, is calling for shoe manufacturers to offer more help to diabetic patients by not only standardising their sizes, but also increasing the range of width fittings available.
In an accompanying editorial, she wrote: "This finding is worrying considering the potential severity of the problems associated with ill-fitting footwear.
"If the number of patients wearing ill-fitting shoes is as great as the present study suggests, there should be a sizeable market for suitable footwear, and considerable economic benefits for the manufacturers who choose to supply that market."