An estimated 12 million Americans a year are misdiagnosed with a condition they don’t have. In approximately half of those cases, the misdiagnosis has the potential to result in severe harm.

Misdiagnoses can have serious consequences on a person’s health. They can delay recovery and sometimes call for treatment that is harmful. For approximately 40,500 people who enter an intensive care unit in one year, a misdiagnosis will cost them their lives.

We talked to three different people, living with three different health conditions, about how a misdiagnosis changed their life. Here are their stories.

My symptoms started at age 14, and I got diagnosed right before my 25th birthday.

I had endometriosis, but I was diagnosed with “just cramps,” an eating disorder (because it hurt to eat due to gastrointestinal symptoms), and mental health issues. It was even suggested that I may have been abused as a child and so this was my way of “acting out.”

I knew something was wrong all along. It was not normal to be bedridden because of period pain. My other friends could just take Tylenol and live a normal life. But I was so young, I didn’t really know what to do.

Because I was so young, I think doctors thought I may have been exaggerating my symptoms. Plus, most people hadn’t even heard of endometriosis, so they couldn’t advise me on getting help. Also, when I tried to talk about my pain, my friends laughed at me for being “sensitive.” They couldn’t understand how period pain could get in the way of living a normal life.

I was eventually diagnosed right before my 25th birthday. My gynecologist performed a laparoscopic surgery.

If I had been diagnosed earlier, say in my teenage years, I could have had a name for why I was missing class and why I was in unbearable pain. I could have gotten better treatment earlier. Instead, I was put on oral contraceptives which further delayed my diagnosis. Friends and family could have understood that I had a disease and wasn’t just faking it or trying to get attention.

My symptoms began in early childhood, but I didn’t receive my diagnosis until I was 33 years old. I’m 39 now.

I have celiac disease, but I was told that I had irritable bowel syndrome, lactose intolerance, hypochondria, and an anxiety/panic disorder.

I never believed the diagnoses that I was given. I tried to explain the subtle nuances of my symptoms to various doctors. They all just nodded and smiled indulgently instead of actually listening to me. The treatments they recommended never worked.

I eventually got sick of regular MDs and went to a naturopath. She ran a bunch of tests, and then put me on a very basic diet that was free from all known allergens. Then, she had me introduce foods at regular intervals to test my sensitivity to them. The reaction I had to gluten confirmed her instincts about the disease.

I was chronically ill for 33 years, from chronic throat and respiratory illnesses to stomach/gut issues. Thanks to the lack of nutrient absorption, I have (and still have) chronic anemia and B-12 deficiency. I’ve never been able to carry a pregnancy beyond a few weeks (infertility and miscarriage are known to occur in women with celiac disease). Additionally, the constant inflammation for over three decades has resulted in rheumatoid arthritis and other joint inflammation.

If the doctors I’d seen so often actually listened to me, I could have gotten a proper diagnosis years earlier. Instead, they dismissed my concerns and comments as being hypochondriac-female nonsense. Celiac disease wasn’t as well-known two decades ago as it is now, but the tests I asked for could have been run when I requested them. If your doctor isn’t listening to you, find another who will.

I had Lyme disease and two other tick-borne illnesses called bartonella and babesia. It took 10 years to be diagnosed.

In 1999, at age 24, I was out for a run. Shortly after, I discovered a tick on my belly. It was about the size of a poppy seed and I was able to remove it intact. Knowing that Lyme disease can be transmitted from deer ticks, I saved the tick and made an appointment to see my primary care doctor. I asked the doctor to test the tick. He chuckled and told me they don’t do that. He told me to come back if I developed any symptoms.

A few weeks after the bite, I started feeling achy, developed recurring fevers, experienced extreme fatigue, and felt run down. So, I returned to the doctor. At this point, he asked if I developed a bull’s eye rash, which is a definitive sign of Lyme disease. I had not, so he told me to come back if and when I did. So despite having symptoms, I left.

Several weeks later I developed a 105°F fever and couldn’t walk in a straight line. I had a friend bring me to the hospital and the doctors started running tests. I kept telling them that I thought it was Lyme disease and explaining my history. But, they all suggested I needed to have the rash for this to be the case. At that point, the rash did appear and they started intravenous antibiotics for one day. After I left, I was prescribed three weeks of oral antibiotics. My acute symptoms resolved and I was “cured.”

I started developing new symptoms like drenching night sweats, ulcerative colitis, headaches, stomach pain, and recurring fevers. Trusting the medical system, I had no reason to believe these symptoms could actually be a consequence of the tick bite.

My sister is an ER doctor and knew my health history. In 2009, she had discovered an organization called the International Lyme and Associated Diseases Society (ILADS) and learned that Lyme disease testing is flawed. She learned that the illness often goes misdiagnosed and that it’s a multisystemic illness that can present as a large number of other illnesses.

I went to support groups and found a Lyme-literate doctor. He suggested we run specialty tests that are much more sensitive and accurate. After several weeks the results concluded that I did have Lyme, as well as babesia and bartonella.

If doctors completed the ILADS Physician Training Program, I could have avoided years of misdiagnosis and saved tens of thousands of dollars.

“[Misdiagnosis] happens more often than it’s been reported,” says Dr. Rajeev Kurapati, a specialist in hospital medicine. “Some diseases present different in females than males, so chances of missing it is common.” One study found that 96 percent of physicians feel that many diagnostic errors are preventable.

There are certain steps you can take to help decrease your likelihood of getting misdiagnosed. Come prepared to your doctor’s appointment with the following:

  • a list of questions to ask
  • a copy of all relevant lab and blood work (including reports ordered by other providers)
  • a short, written description of your medical history and current health condition
  • a list of all your medications and supplements, with dosages and length of time you have been on them
  • progress charts of your symptoms, if you keep them

Take notes during appointments, ask questions about anything you don’t understand, and confirm your next steps after diagnosis with your doctor. After a serious diagnosis, get a second opinion or ask for a referral to a medical professional that specializes in your diagnosed condition.