Show it to your doctor. He or she should ask for a family medical history when you first visit. If there's something that stands out-early onset of cancer in several close relatives, for example, or a continuous string of men who died in their 50s from a heart attack—he or she may recommend (or you can ask about) a visit to a genetic counselor, says Roizen. In some cases, your actual medical care may change. For example, a strong family history of colon cancer or polyps may mean you should be screened before the usual starting age of 50. A family history of prostate cancer may tilt you in favor of taking the controversial prostate specific antigen, or PSA, test. And a family history of heart disease may mean a discussion with your doctor about taking daily aspirin.
Learn from it. Even if there are no additional medical steps to take, knowing you have an elevated risk may inspire you to focus on factors you can control: tobacco use, diet and weight, physical activity, or alcohol use, says George Kikano, professor and chair of the department of family medicine at Case Western Reserve University. It's rare that a gene destines you to a certain disease; more likely is that you're simply at higher risk than the average person. And in many cases you can modify that risk. "I look at it this way," says Roizen. "Every one of us has genes that make us vulnerable. Very few of us know which ones they have, and family history gives us clues."
Share it with your relatives. If you and your grandmother both had breast cancer in your 40s, that's information your children will need to have some day. Yes, even boys—they might be at higher risk of breast cancer themselves and also may pass on a mutation to their future daughters, Garber says. Your siblings, nieces, and nephews may also benefit from the information you find. So in the spirit of family, offer to share.