This post originally appeared on Shape.com

In a perfect world, you’d walk into the doctor’s office with a medical question and walk out with a diagnosis, a treatment plan, and a ride home from Channing Tatum.

In real life, things don’t always work out that way—and having Magic Mike in the driver’s seat may not be the only far-fetched part of that scenario. Primary care docs may miss or misidentify a wide range of common conditions. In a study last year in JAMA Internal Medicine, researchers looked at 200,000 appointments and found 190 diagnostic errors. Of those, one-third could have caused serious harm. In fact, researchers at Johns Hopkins estimate that more than one million Americans each year get hurt because their doctors came to the wrong conclusion. And while docs get it right more than they get it wrong, certain conditions are more likely to slip through the cracks than others.

What Doctors Miss Most
1. Depression. As many as one in four patients with depression leaves the doctor’s office without having their condition recognized, research shows.
2. Celiac disease. Many people have this severe reaction to gluten for a decade or more before receiving an accurate diagnosis, according to the National Institute of Diabetes and Digestive and Kidney Diseases.
3. Thyroid conditions. With subtle signs like fatigue, problems with this gland often masquerade as the effects of stress and sleep deprivation, says New York University gastroenterologist Roshini Raj, M.D.
4. Appendicitis. The main symptom—abdominal pain—can signal many different problems. So about one-third of young women with appendicitis are told they have something else, including gastroenteritis (better known as stomach flu) or a urinary tract infection.
5. Stroke. A recent study in the journal Diagnosis found more than one in 10 people who had strokes went to the hospital with headaches and dizziness within the previous month—and were sent home without treatment. Women and younger adults faced a greater risk of misdiagnosis.

On the flip side, some are over-diagnosed. For instance, blood tests spot lupus in five percent of people who don’t have it, notes the Centers for Disease Control and Prevention. What’s more, your internist or family physician doesn’t always have the tools, time, or expertise to treat complex psychological, gastrointestinal, or autoimmune disorders. Take obesity: Two-thirds of U.S. adults are too heavy, but a recent survey found only 39 percent have been told so by a doctor—and one in three who were instructed to lose weight said they weren’t given any guidance on how to do it.

Pointing the Finger
Doctors, patients, and the health system as a whole share the blame for these missteps. If your physician doesn’t see many people with certain conditions—say, eating disorders—he or she may not even think to consider them as potential explanations for unusual weight gain or loss, says University of Alabama dietitian Sheena Quizon Gregg, R.D.

And when it comes to treatment, a complicated condition like obesity presents unique challenges: “It requires specialized training not taught in med schools or residency training, along with lots of time, support, and a comprehensive approach, which is impossible in a primary care visit of 15 minutes,” says Arizona weight-loss physician Robert Ziltzer, M.D.

And yes, you’re part of the problem too. In the case of psychological illnesses like depression, you may feel too ashamed to bring up your symptoms. Or it might not even occur to you that the same person who treats your strep throat could help with issues like sadness and sleep disturbances, says Richard Kravitz, M.D., a professor of internal medicine at the University of California Davis School of Medicine.

Protect Yourself
The good news, though, is that you’re also part of the solution. While physicians should certainly strive to get things right as often as possible—and most do—patients can increase their chances of receiving the right diagnosis and effective treatment. Here, five ways to do it.

1. Document your past. Instead of Googling rare and life-threatening conditions, spend your precious pre-appointment time making a detailed list of your symptoms, when they began, how they changed, and what makes you feel better or worse. A detailed medical history often provides about 90 percent of the information your doctor needs to diagnose you, while tools like lab tests and X-rays fill in only the remaining 10 percent, Kravitz says.

2. Be honest. Sure, you might squirm as you spill the details of your one night stand, how much you really drink at happy hour, or whether you struggle to control your eating behaviors. But your doc needs the full scoop to pinpoint your problem and find the best solution, Raj says.

3. Ask about other options. Merely posing a question about your symptoms: “Is there anything else that could be making me feel this way?” or “Could this be depression?” can take busy doctors off autopilot. The answer may be “no,” Kravitz says, but asking gives him or her a chance to consider alternatives (and explain the reasoning if they’ve been ruled out).

4. Let your doc do his job. Sure, your college roommate may have had a brain tumor—but that doesn’t mean you should demand an MRI each time you have a headache. Excess testing poses its own risks, such as radiation exposure, false positives, and big medical bills. Plus, it can lead physicians too far astray from more obvious causes of your problems, Kravitz says.

5. Seek a second opinion. Take your issues elsewhere if your doc routinely dismisses your questions or opinions, Kravitz says. But even if you two get along, you may want to consult someone else if you’re not feeling better after a reasonable amount of time. Don’t feel guilty—most M.D.s will welcome additional input if they’re stumped, Raj says. Also consider asking for a referral to a specialist if you have more than 20 pounds to lose or if you’re concerned that an issue like depression or an eating disorder poses an immediate threat to your life (or a friend’s), say Ziltzer and Gregg.