If there’s a bug going around the office and you wake up with some of the same symptoms, you’ll likely assume you’ve got it, too. Most doctors think the same way. If he or she sees three people with colds in one day, it would be an easy guess that the next person with a stuffy nose and fever has the same thing.

The problem is that a lot of conditions share symptoms, and it can be misleading if not all the symptoms show up. This makes it easy to make a misdiagnosis—as many as one in five diagnoses are incorrect or go undiagnosed.

For women, the most commonly misdiagnosed conditions include ovarian cancer, autoimmune disease and hormonal imbalances. Heart disease, for example, is more common in men. When women experience the same symptoms, especially young women, a doctor may consider stress to be the cause instead.

The best way to avoid a misdiagnosis is to share all of your symptoms. Seeing the same doctor doesn’t hurt, either. When you and your doctor know your history and get the full story, it’s harder to miss the little details that make a big difference. Finally, don’t be afraid to do some research before your appointment and don’t be afraid to ask questions.

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