You leave your doctor's office with a prescription—and every intention of filling it. But then you never make it to the pharmacy, or you discover that your insurance plan doesn't cover that brand.
Even if you do get the pills, you might forget to take one, or you might toss them halfway through your treatment because you're feeling better. Then, when you go for a follow-up, you say, "Of course, I took them!"—despite your doc pointing out that your symptoms are still there.
Why you should spill: As embarrassing as it might be to admit it, "If you don't tell us you're skipping pills, we'll assume you're taking them and they aren't working, so we might change the dosage or the prescription"—which may put off your recovery and cause side effects, says Laura Knobel, MD, a family physician in Walpole, Massachusetts, and a member of the board of directors for the American Academy of Family Physicians.
2. "I'm doing a cleanse to lose 10 pounds."
You spent a week consuming nothing but lemon juice and cayenne pepper—and you know your doc won't approve.
Why you should spill: Any extreme diet—from those involving laxatives or stimulants to "healthier" versions (like juice fasts)—has its risks even if you're in good shape and follow it for just a few days. You can become dehydrated and throw off your electrolyte balance, which can harm the heart and kidneys, for starters.
3. "My sexual past isn't what it seems."
It's not easy to sit in a paper robe ticking off how many people you've had sex with or—even more difficult—admitting that you've been a victim of sexual violence.
Why you should spill: When your doctor asks about your sexual partners, it's not so she can judge your choices; it's to assess your risk for STDs and to schedule appropriate screenings.
4. "My family's health history is not so perfect."
Discussing your father's cirrhosis or your sister's battle with depression during a routine checkup might strike you as irrelevant; it might also dredge up grief, or fear. No wonder you don't want to mention it.
Why you should spill: If you have a family history of colon or breast cancer, for example, your doctor can advise you about screenings that could catch these scary diseases in their most treatable stages. And if depression, heart disease, or high blood pressure runs in your family, you can work out an action plan now for staying healthy down the road.
5. "I'm cheating on you."
When you see another doctor on the side, you might keep quiet to spare your physician's feelings, the way you wouldn't want to hurt your boyfriend by telling him you had drinks with a cute co-worker.
Why you should spill: There's no need to have a break-up talk with your doctor if you're leaving him—but if you're seeing two doctors at the same time, things can get dicey. "You need to tell each one what the other one is doing," Dr. Gallin says. "They need to be able to share test results, make sure there aren't any bad drug interactions, and ensure that their treatments work together."