Humans boast at least five senses. Dogs seem to have a few more—as evidenced by the fact that they can sense illness and medical conditions in humans before the humans have any idea.

Migraines 

According to a University of Pittsburgh study, dogs that live with people who suffer from migraines are able to notice subtle changes in their owners’ disposition that kick in when the severe headaches do. Amazingly, the dogs can sense that something is wrong up to two hours before the human demonstrates migraine symptoms. (One person in the study said that before she got the brunt of her migraine, her dog would bark, frantically wag its tail, and walk around in circles.)

Narcolepsy

Probably the most famous (and frightening) of all sleep disorders is narcolepsy. In severe cases, sufferers may fall asleep at random during the day, even if they got a good night’s rest the night before. It’s caused by the lack of hypocretin, a chemical in the brain that regulates awakeness and sleep.­ When a narcoleptic episode is about to strike, the body releases a nearly undetectable odor…undetectable by humans, that is. Researchers say that dogs can smell (and warn of) the onset of a bout of sudden sleepiness up to five minutes before their human can, which provides enough time for the person to get to a bed, pull over to the side of the road, or take emergency medication.

Diabetes

A telltale sign that a person has diabetes—or that a diagnosed diabetic needs to be hospitalized—is a condition called diabetic ketoacidosis. The body can’t make or use insulin to properly turn food into energy, and it starts breaking down fat instead, spilling a substance called ketones into the urine. It also reveals a slightly fruity or acidic scent in a person’s breath. People usually can’t smell their own breath, but dogs can…which is why some have been trained as assistants for diabetic patients. The dog can smell the ketoacidosis, and alert their human to it, before they pass out (or worse).