Washington, D.C. ? Diabetics, watch out: A hot spot on your foot can signal an ulcer is brewing, a wound that could cost your limb.

New research shows that using a special thermometer to measure the temperature of their soles can give patients enough early warning to avoid one of diabetes’ most intractable complications.

It’s a simple-sounding protection for such a huge problem. Foot ulcers each year strike 600,000 U.S. diabetics, people slow to notice they even have a wound because diabetes has numbed their feet.

“They’ve lost the gift of pain,” says Dr. David Armstrong of Chicago’s Rosalind Franklin University of Medicine and Science, a diabetic foot specialist.

Worse, foot ulcers are so slow-healing and vulnerable to infection that they’re to blame for most of the roughly 80,000 amputations of toes, feet and lower legs that diabetics undergo each year.

So word that an easy-to-use gadget could help is generating excitement. Using the thermometer reduced by nearly two-thirds the number of high-risk patients who got foot ulcers, Armstrong found in a study of 225 diabetic veterans, the third in a series of government-funded research to back the approach.