A man in the United States has credited his dog with saving his life after it chewed off his diseased big toe as he lay passed out in a drunken stupor.

Michigan man Jerry Douthett, 48, woke up on a Saturday night in late July in his Rockford, Michigan home to find his Jack Russell Terrier, Kiko, had gnawed off his right big toe.

"The dog always lays with me on the bed," said Mr Douthett.

"That night, I woke up and looked down at my foot, and it was wet. When I looked it was blood, and there was the dog looking at me with a blood moustache."

Mr Douthett's wife, Rosee, rushed him to a hospital where doctors found he was suffering from type 2 diabetes.

Doctors found his toe was badly infected and surgeons amputated the remainder of the digit.

Ms Douthett, a registered nurse, had been urging him for weeks to have his infected toe examined by a doctor.

On the night Kiko ate his toe, Mr Douthett said he had been out with his wife and drank about "six or seven beers" and a pair of giant margaritas "big enough to put goldfish in".

"I was self-medicating at this point," he said.

"The moral of the story is that the dog saved my life, because otherwise I never would have gone in to see a doctor."

The couple said they were amazed that Kiko appeared to know Douthett had an infection that needed treatment.

"He kind of chewed off the infected part and stopped at the good bone," said Ms Douthett.

"We joked that we shouldn't have had to pay the co-pay because he did half the job by chewing off half of the toe."

- Reuters