How much do you really know about your doctor?

It could be dangerous to just assume he or she knows what they’re doing.

Medical errors are the third leading cause of death in the United States, according to a 2016 study by doctors at Johns Hopkins Medicine.

You’ve likely heard the headlines before: A sponge left inside a patient after surgery; scalpels and scissors forgotten; the wrong leg amputated; the right side of the skull opened when it was supposed to be the left.

Phoenix-based attorneys provided 12 News some local examples, such as drugs that should not have been prescribed, surgeons performing surgery while under the influence, or hernia procedures that turned deadly.

The patients who survive mistakes often have to live with the impacts of the medical errors for the rest of their lives—which are often shortened.

But some mistakes are deadly.

For example, a flesh-eating bacteria was mistaken for the flu for a patient in Ohio. The patient returned the hospital to get the right diagnosis and died five days later.

Another case went to court, where the plaintiff won $22 million after she suffered permanent damage to her vocal cords during a procedure on her leg.

Medical errors claim a shocking 250,000 lives a year in the U.S., according to a 2016 study by doctors at Johns Hopkins Medicine. Meaning, medical error would rank third on the Centers for Disease Control and Prevention’s list of leading causes of death. That would place it just below heart diseases and cancer.

Another way to look at it—medical errors kill more people than car crashes and homicides combined.

Deb Saeed Gay lost her son just before Christmas in 2014. She says he was misdiagnosed by emergency room doctors and released.

“He used to bring [Christmas] to life,” said Gay.

Ten-year-old Isaiah went into the emergency rooms at Swedish Medical Center near Denver with flu symptoms. Less than an hour later after leaving, the boy collapsed while his father filled his prescription at a pharmacy. Isaiah suffered irreversible brain damage and later died.

“Without him here … I don’t feel Christmas anymore,” his mom said.

In a wrongful death lawsuit, the parents claim the boy had treatable diseases that were not diagnosed. They said they weren't concerned about money. They just didn't want it to happen to anyone else.

“You’re always going to have that grief,” said Gay. “You’re always going to have that person missing. You just have to learn to live without them.”

Swedish Medical Center representatives only commented they were surprised by Gay's accusations. They did not comment on the lawsuit, which is still pending.

For the sake of illustration, let’s assume all deadly medical errors happen in hospitals. There were about 126 million hospital visits in the last year, according to the CDC. That means only 0.002 percent of the visits resulted in death.

Factor in other scenarios where medical errors can occur—at the clinic with your primary care physician, at a physical therapy session or other outpatient care—and the number drops even lower.

Medical errors can be catastrophic, but they are also extremely rare.

Sometimes more stressful than dealing with the mistake is the legal process that follows, especially if you don’t have solid proof.

“It’s difficult or almost impossible to prove whether or not a malpractice caused the death,” said Kevin Tucker, a Phoenix-based medical malpractice attorney.

“Litigation is traumatic. To force somebody to go through so the attorney can make a profit,” is not right, he said, adding it often costs somewhere between $30,000 and $50,000.

Banner Health was the only health care organization (local or national) to respond to our request for input on this story. A spokesperson said patient safety is a top priority.

In a statement, Banner highlighted a list of practices in place in its care environment, such as providing two sets of caregivers to patients in the intensive care unit and using decision-making technology that provides a notification if a choice of care isn’t consistent with evidence-based practices. The statement reads:

At Banner Health, patient safety is our first responsibility. Here are a few highlights of the practices we use to protect patients in our care environment:

• Caregivers at all levels demonstrate their skills in Banner’s simulation hospital– one of the largest in the country– before they work in direct patient care.

• We use sophisticated bedside decision making technology that suggests next steps in care and provides notification when care is not consistent with evidence-based practices.

• We closely monitor infection rates and intervene when performance in a specific clinical area does not meet our standards.

• In our intensive care units, we utilize eICU technology that enables each patient to have two sets of expert caregivers. They have a clinical team at the bedside, and also a remote team of critical care providers that is constantly monitoring their vital signs for changes.

• If an adverse event does occurs, we address it in a no-fault environment in order to best understand the cause of the event, and look for improvements in training or process so future events can be avoided.

But errors still happen.

The question is: How do you prevent them from happening to you or your loved one?

The advice may seem like common sense, but few people follow it.

First, ask questions–lots of them!

“Who do you think does this as well as you? Who else would you recommend I have look at my situation?” are questions Kyle Israel, another medical malpractice attorney in Phoenix recommended.

Secondly, get a second opinion.

“Find out if you have multiple options,” he said.

You can also ask the doctor how many times he or she has performed the recommended procedure.

Another tip is to find out if the doctor has had issues with unprofessional behavior, fines, probation or other disciplinary actions in the past. Some of their history is available on the Arizona Medical Board’s website.

If you are going into surgery, make sure the body part being operated on is clearly marked before you go under.

Some of this information can be scary. But before you swear off seeing your doctor, you should know the same research cited above also shows most medical mistakes aren’t because the doctors are bad medical professionals. Most errors are because of systemic problems, such as poorly coordinated care, problems with insurance networks, and not having backup plans.

Another piece of advice from the attorneys mentioned above: Tell your doctor "I don't know" is an acceptable response to your questions as long as they are willing to ask someone who does know the answer.