For decades, specially trained dogs have helped people manage health issues such as hearing impairment, blindness, and autism. More recently, man's best friend has been paired with individuals with a seemingly unrelated disease: diabetes.

A dog's nose consists of more than 220 million scent receptors - over 1,000 times more than that of a human. Diabetic alert dogs (DADs) have been trained to alert diabetic patients when their blood sugar levels peak too high or drop too low. DADs pick up on volatile organic compounds excreted in sweat, urine, saliva and pulmonary vapors. Although science has yet to explain the exact diabetes-related compounds dogs are able to smell, experts at the Endocrinology Network suggest it likely has something to do with ketosis products.

Sarah Breidenbach, who was diagnosed with type 1 diabetes as child, now uses her 5-year-old service dog in her home of St. Paul, Minnesota. The black Labrador named Moxie sniffs out when Breidenbach's blood glucose is too high or too low - simply by smelling her breath. When she detects a distinct, potentially dangerous odor, Moxie goes into alert mode. She jumps, whines loudly, paces and stares directly into Breidenbach's eyes until her owner checks her blood sugar.

Though still rare, diabetes alert dogs have been emerging as part of diabetes care. Can Do Canines, a training organization in New Hope, Minnesota, estimates that there are only about 150 diabetes alert dogs nationwide.

So how does it really work?

Lily Grace, a registered nurse and founder of the National Institute for Diabetic Alert Dogs, explains that changes in body chemistry appear in body secretions up to 15 to 30 minutes before showing up in the blood. That means values from home blood glucose meters or continuous glucose meters lag behind what a well-trained DAD may smell. Notably, a retest is required about 10 to 15 minutes after an alert is signaled from the dog.

The pre-warning may help tighten control of patients' glucose levels by alerting them that there is a change happening so that they can take appropriate action. However, Grace emphasizes that there are limits to dogs' capabilities.

"It doesn't mean you don't treat without testing," Grace told the Endocrinology Network. "The dog is typically faster than a CGM, but CGMs give a number and the dog does not. It's still a dog, and dogs will occasionally miss a low. So it's always a combination of tools. It is absolutely critical that people know this."

Typically, DADs are placed with individuals with type 1 diabetes more than those with type 2 diabetes.

Scientific information

Diabetes research on DADs is still few and far between, but it seems to confirm observations of owners and trainers. In one survey of 212 owners with this type of dog, 65 percent of them reported that these dogs showed behavioral reactions to at least one hypoglycemia episode. About 34 percent of owners believed their dog's reactions happened before they were personally aware of the incident.

Another survey of 36 DAD owners reported significant decreases in severe hypoglycemia. A total of 75 percent explained that they experienced improved quality of life with their DAD.

To learn more about diabetic alert dogs:

Restoring Freedom — Diabetic Alert Dogs
Foundation Helps Those with Type 1 Diabetes Get Alert Dogs
Predict Your Blood Sugar 30 Minutes in Advance