Anne Wills of Halethorpe found that out in an amazing way, when her dog detected that she had lung cancer.
Like most all dogs, Heidi loves to play. But the eight-and-a-half year old Shepard-Lab mix also has a day job she takes very seriously.
"In her almost eight years of working, she herself has gotten almost 2,000 animals home," said Anne Wills, founder of Dogs Finding Dogs, a canine search and rescue team that's dispatched to find missing pets and people.
"She's saved a lot of lives," Wills said. "I just never thought she would save mine."
"I often say that Heidi has the equivalent of two PhD's," said Dr. Enser Cole, Wills' oncologist and chief of Medical Oncology at Saint Agnes Hospital. "In this case, a dog diagnosed the cancer before the doctors did."
You read that right. Heidi detected her owner's cancer.
"Not having any symptoms whatsoever, I didn't know there was anything wrong," Wills said.
Back in February, Heidi started acting very distressed. She pawed at Wills' arm over and over again.
"She's progressively getting more and more aggressive with that behavior and then she started taking her nose and burying it in my chest and sniffing very, very hard," Wills said.
After a vet determined nothing was wrong with Heidi, Wills went to her primary care doctor to get checked out herself.
"Told the doctor the story, he sent me for a CAT scan and the next morning he was calling me telling me that he sees three spots of what looks like cancer," she said. "It was right where Heidi was smelling in my chest."
The early detection very likely saved her life.
"When they come when they develop symptoms, which is usually when we first see them, they typically, already have advanced stage lung cancer that isn't curable," Dr. Cole said, adding that what Heidi did is unusual, but it isn't unheard of.
"I think it's a testimony to Mrs. Wills devotion to her dog, the dog's devotion to her," he said. "The high training that Heidi has in using its special super sensitive nose to track people, lost pets, detect narcotics, and in this case, detect the presence of a lung cancer."
Wills' cancer is now in remission, and while not everyone has a Heidi, Wills hopes her story helps others.
"Listen to your pet, your dog," she said. "Not saying every dog, every time they smell you, it's something bad, but if you see something like my situation, at least, stop and think, 'Should I go to the doctor?'"
Dr. Cole said the hope is to be able to identify the chemical that the dog is smelling when there's cancer present. For now, he recommends people who are 55 to 75 and moderate to heavy smokers at some point in their lives, to undergo annual low-dose CAT scans to detect lung cancer.