The dogs seem to sense a dangerous drop in blood glucose before it begins, allowing the people to prevent an episode altogether, reports the March issue of Diabetes Forecast, the consumer magazine of the American Diabetes Association.

Mark Ruefenacht, a forensic scientist with type 1 diabetes who started a hypoglycemia alert dog training center in California and who has placed trained dogs for three years, said some dogs also seem to sense high blood glucose.

"Clients are coming back saying, 'I have never had better control of my blood sugar in my life as I have since I got this dog.'" Ruefenacht said in a statement.

Scientists said they are unsure about how the dogs are able to sense the glucose changes in humans, but some think the dogs are reacting to scents created by chemical changes related to glucose imbalance.

"The first time that dog gets you up in the middle of the night because your child is dropping into a serious low, rapidly you realize it's worth every penny you spent, and every minute you had to wait," Donna Cope, whose child has diabetes, told Diabetes Forecast.