Getting a misdiagnosis by the doctor can be dangerous, even deadly.
One study has shown that nearly 126,000 Americans die each year because doctors aren't diagnosing common diseases like hypertension, heart attacks and pneumonia. Here's a look at some of the most common medical misdiagnoses.
"I probably had it a good 10 years before it was diagnosed," said Margaret Tischer, who finally found out she had sleep apnea a couple of years ago.
Tischer, 52, didn't realize how much it was affecting her life until she started treatment.
"I wake up easier in the morning sometimes and you do find that you have more energy," Tischer said.
Inova Fairfax Hospital pulmonary specialist Dr. Barry Dicicco said he sees many patients who've suffered from sleep apnea for years because they've received the wrong diagnosis. Often, they're told it's depression.
"Sleep deprivation can lead to irritability, lack of memory and generalized malaise," Dicicco said.
But it's not just sleep apnea that's a problem. Doctors could be giving a wrong diagnosis more often than you realize, and it's happening with some common diseases.
"It's typically conditions that are fairly subtle," said family medicine Dr. Tiffini Lucas.
Lucas said she sees it all the time.
"A lot of time we get patients, especially women, who have a lot of vague, non-specific symptoms and you have to dig a little to find the cause," Lucas said.
Thyroid problems are a big problem, for example. She said those can easily be mistaken for stress when the patient is a woman.
"Often women will come in with complaints that you can see everywhere -- fatigue, inability to lose weight, sleep problems and some people may write that off as stress, but it could actually be an underactive thyroid," Lucas said.
Sometimes a misdiagnosis can delay important treatment. Lucas points out that heart disease is often not picked up soon enough in women. Their symptoms can be very different from men's and doctors can easily make mistakes.
For men, cancer is often missed by doctors. Prostate and colon cancers are misdiagnosed because they can have subtle symptoms.
"Even though there are plenty of studies and groups that are recommending the screenings be done, we find that men still aren't getting the screenings done," she said.
The best way to avoid a misdiagnosis is to follow your instinct. If you're not getting better after your prescribed treatment, don't be afraid to go back to the doctor, Lucas said.
"If a patient has symptoms and you don't feel like you're getting the right answer, than I think you should push your doctor a little bit," she said. "You are your best advocate when it comes to your health."