5 Lies You Shouldn't Tell Your Doctor

There isn't a lot your body can hide in one of those crinkly numbers. Maybe that's why so many women refuse to reveal much else at doctor visits. About a third of men and women in the United States admit to lying to their M.D.'s, according to a 2010 survey. But keeping secrets can be dangerous, especially if the information you're withholding leads to a wrong diagnosis. Besides, "a doctor's job is to advocate for your health, not judge," say Gary Fischer, M.D., a general internist at the University of Pittsburgh Medical Center. Here's why it's time to tell the whole truth -- and nothing but.

"I never smoke."

The real deal: Jean Thilmany has been lighting up a couple of times a month for the past 20 years. But because the 42-year-old Saint Paul resident doesn't consider herself a smoker, she never mentions it to her doctor. "I don't smoke often enough for it to affect my health," she says. Actually, if you puff even the occasional cigarette at happy hour, your doctor needs to know. Yes, cancer is a concern, but equally important, those smokes affect your circulation and increase your risk for blood clots.

"Nothing has changed since my last visit."

The real deal: Really? When your doctor asks "What's new?" she doesn't mean only medically. Whether you're in a tense relationship or fretting about work woes or money matters, chronic stress can trigger high blood pressure, migraines, tummy troubles and heart palpitations, Dr. Fischer says. "The stress hormone cortisol throws other hormones, like estrogen and progesterone, out of kilter," says Jerilynn Prior, M.D., director of the Centre for Menstrual Cycle and Ovulation Research at the University of British Columbia. This does more than mess with your period: Estrogen helps prevent bone loss, and progesterone aids bone growth.

The good news: Although prolonged periods of stress can have serious health consequences, there is a lot you can do. Talk to your physician; she can suggest stress busters, like relaxation exercises and yoga. In some cases she may recommend that you speak to a mental health professional who can help you work through your problems.

"I'm not taking anything."

The real deal: More than 50 percent of Americans take supplements, according to the Centers for Disease Control and Prevention. The few natural remedies that you use may not seem noteworthy to you, but they are to your physicians. "A decade ago many women took Saint-John's-wort for PMS only to learn that it can make birth control pills less effective," says FITNESS advisory board member Mark Moyad, M.D., director of preventive and alternative medicine at the University of Michigan Medical Center. And that's not the only interaction your physician wants to watch out for. Using ginseng with antidepressants puts you at risk for serotonin syndrome, a potentially fatal condition that causes diarrhea, fever and seizures. Because fish oil can thin the blood, you should stop taking it a week before dental work or surgery and don't combine it with another blood thinner, like aspirin, without checking with your doctor. Too much vitamin D can cause kidney stones, while too much vitamin C can cause heartburn. So make a list of the pills you pop, including vitamins, supplements and meds (OTC and prescription), and bring it with you to your appointment.

"I feel fine."

The real deal: About one in eight women struggle with depression at some time, but recognizing that you need help isn't easy. Twice as many women as men are affected. In addition to having persistent feelings of sadness, guilt, hopelessness and irritability, depressed women may gain or lose weight. "Tell your physician about any significant changes in your mood, thinking or behavior that affect your ability to function at home, at work or with your friends," says David Fassler, M.D., clinical professor of psychiatry at the University of Vermont College of Medicine in Burlington. She'll probably rule out other potential causes, such as viruses, thyroid disorders and medication side effects, and then conduct a psychological evaluation herself or refer you to a mental health expert. The happy news is that there are many treatment options, including psychotherapy and antidepressants.

"I eat a healthy diet."

The real deal: After three days of swigging nothing but a concoction of lemon juice, maple syrup and cayenne pepper, Catherine Howe Bryant, 32, felt light-headed, lethargic and, not surprisingly, famished. "I dropped a few pounds, but I felt awful," admits the Winston-Salem resident. Still, Bryant does a liquid cleanse whenever she wants to "feel better" about her body. She's never told her doctor. What she and other women don't realize is that extreme diets can do real damage. "When your body doesn't get the protein it needs to generate new cells and tissue, it starts to burn muscle tissue, including the heart's cardiac muscle," says Arthur Frank, M.D., medical director of the George Washington University Weight Management Program in Washington, D.C. This can lead to heart palpitations, arrhythmias and many other cardiac problems. Putting yourself into starvation mode slows your metabolism in the short term and ultimately makes it difficult to maintain weight loss.

Whether you're trying to slim down for a beach vacay or training for a race, clue your doc in. She can help you devise a sensible plan and refer you to a nutritionist for a dietary tune-up that's safer than a detox or cleanse.