By Marisa Cohen

Let’s be honest – when it comes to confessing your most personal issues to doctors, it’s tempting to fudge the details, whether it’s those diet pills you borrowed from a friend or that fling you had with a neighbor.

You keep quiet for seemingly good reasons: You don’t think it’s important, you’re embarrassed, you feel rushed – or, most likely, you simply don’t want to look bad, says Barbara Korsch, MD, a professor at the University of Southern California Keck School of Medicine and author of The Intelligent Patient’s Guide to the Doctor-Patient Relationship.

“We tend to believe that if our doctor likes and respects us, we’ll receive better treatment,” she says. But revealing all can do more than just improve the quality of your health care – in some cases it may even save your life. We talked to top MDs to find out the most common secrets women keep, and what you gain by telling the truth.

1. “Those pills you prescribed? I haven’t been taking them.” 
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. And when you toss antibiotics before you’re done with the full course, you may not kill off all the infectious bacteria in your body, leaving them resistant to drugs and possibly causing the illness to come back with greater force. If money is an issue, talk to your doctor about switching to a less-pricey medication, rather than borrowing pills (they may be expired or the wrong dose for you). Bring up, too, any herbal supplements you’re taking – they’re still medicine and may not mix well with your prescription.

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. “Cleanse diets can also strip you of micronutrients like magnesium and vitamin D,” says Pamela F. Gallin, MD, author of How to Survive Your Doctor’s Care. Talk to your doctor about a better weight-loss plan—or, if you’re going to do the cleanse anyway, at least check in to ensure you’re going about it as safely as possible.

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. Some types of human papillomavirus, for example, can lead to cervical cancer if not treated; untreated chlamydia can lead to infertility, and herpes can lie dormant but be passed on to your future babies, says Cheryl Iglesia, MD, director of female pelvic medicine and reconstructive surgery at Washington Hospital Center, in Washington, D.C. That’s why it’s also crucial to tell your gyno if you or your partner have had an affair or you were once sexually assaulted. (Dr. Iglesia suggests that you schedule a separate appointment to talk about these sensitive subjects, so you don’t feel rushed during your annual exam.) Your doctor can also help make your sex life better, but only if you’re willing to open up about it. “Low libido is very common, and there are several treatments for it, from hormones to couples therapy,” Dr. Iglesia says.

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.

Dr. Knobel also points out that when a doctor’s questions seem to come from left field – like asking about depression when you’re suffering from back pain – there’s usually a method to the seeming madness. Your symptoms could be caused by a not-so-obvious condition, and your family history may point your doc in the right direction.

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.” That’s true whether you “cheat” with a traditional doctor or an alternative healer. “We need to know what you’ve tried,” says Dr. Knobel, who adds that it’s often easier to get reimbursed for tests, such as MRI, if a patient has already tried physical therapy or a chiropractor. “Think of your main doctor as your home base, the one who keeps track of everything,” Dr. Knobel says. “If you’re not comfortable sharing all that information with her, then you may want to look for another doctor.”