When you receive a diagnosis from your doctor, chances are, you believe it. After all, physicians are medical experts with years of experience identifying a variety of diseases. They've probably seen hundreds, if not thousands, of patients with symptoms just like yours.

But doctors are also human beings who can make mistakes. And certain diseases can be hard to diagnose or may manifest themselves differently from patient to patient. For all these reasons, millions of Americans are misdiagnosed every year—a problem that can lead to serious health complications and even death.

Protecting Yourself

To prevent misdiagnosis, provide your doctor with a detailed history of your illness and as much information as possible about your symptoms. If you're not satisfied with your diagnosis, ask for more tests, and question your doctor about what else your symptoms could mean. Be especially careful if you suspect that you or a loved one may have any of these frequently misdiagnosed conditions.

  1. Cancer. Being diagnosed with cancer can be terrifying, but not being diagnosed if you have it is far worse. A Harvard study found that cancer, primarily the breast and colorectal types, is the most commonly misdiagnosed disease, and experts say this is due to doctors failing to stick to screening guidelines. In fact, singer Kylie Minogue reported that her breast cancer was initially misdiagnosed.
  2. Infection. The same Harvard study found that infection was the second most misdiagnosed disease, in part because many infections share symptoms that are similar to those of other conditions. Some of the most commonly misdiagnosed forms include ear infection, yeast infection, sinus infection, and pertussis infection (whooping cough).
  3. Aortic dissection. With this potentially life-threatening condition, there is bleeding into and along the wall of the aorta, the major artery leaving the heart. But the disease frequently gets misdiagnosed as heartburn because of sensations felt in the chest. It is believed that actor John Ritter died of an aortic dissection that had been misdiagnosed.
  4. Clogged arteries. When the arteries become clogged with fatty deposits called plaque, it leads to coronary artery disease—the leading cause of death in the United States for both men and women. Despite its prevalence, though, doctors often misdiagnose the condition because they attribute symptoms, such as shortness of breath, to the side effects of being overweight rather than to clogged arteries.
  5. Heart attack. How could a heart attack be misdiagnosed? Well, they're not always as obvious as the ones we see on TV; sometimes, the only symptoms are a sense of fullness in the chest and nausea. A study conducted by the New England Medical Center in Boston found that one in every 50 heart attack victims are mistakenly sent home by emergency room doctors, and other studies suggest that misdiagnosis rates may be even higher.
  6. Celiac disease. Celiac disease is a digestive condition triggered by eating the protein gluten, which is found in bread, pasta, cookies, and many other foods containing wheat, barley, or rye. It is most frequently misdiagnosed as irritable bowel syndrome, Crohn's disease, or even chronic fatigue syndrome or depression.
  7. Bacterial meningitis. Bacterial meningitis causes a swelling of the lining around the brain and spinal cord, and it can kill its victims in hours. Symptoms include fever, vomiting, severe headache, stiff neck, sensitivity to bright lights, sleepiness, confusion, rash, and seizures. From this list, you can guess how it could be easily mistaken for influenza.