An experimental patch that could automatically deliver doses of insulin to patients with diabetes has been successfully tested in lab animals, researchers said.

If trials in people are shown to work, the patch could offer a less painful alternative for people who must otherwise use needles to inject themselves with insulin.

Researchers at the University of North Carolina and North Carolina State described the product as "the first smart insulin patch that can detect increases in blood sugar levels and secrete doses of insulin into the bloodstream whenever needed."

The patch itself is about the size of a penny and contains more than 100 tiny needles, each about as big as an eyelash, according to the study in the Proceedings of the National Academy of Sciences.

Each microneedle contains "microscopic storage units for insulin and glucose-sensing enzymes that rapidly release their cargo when blood sugar levels get too high," said the study.

In mice with diabetes, those treated with the microneedle patch saw their blood glucose levels brought under control within 30 minutes, and stayed that way for several hours.

Mice that were injected with insulin saw blood sugar levels return to normal, but they required another shot sooner than the patch-wearing lab animals.

"If we can get these patches to work in people, it will be a game-changer," said John Buse, co-senior author and director of the UNC Diabetes Care Center.

Diabetes affects more than 387 million people worldwide.