We look up to doctors, so it’s easy to think they know everything there is to know about health care. 

Indeed, most doctors are exceptionally smart, take their work seriously and look out for their patients’ best interests. But despite their best intentions, doctors aren’t perfect. To that effect, here are some things they’ll probably never admit to patients.

‘I'm not fully knowledgeable about health insurance or costs.’

They might have a general idea about the financial aspects of health care, but doctors are experts in physiology and medicine. That job takes a lot of time and dedication on its own, with little left for administration and finance. It’s a different expert who handles billing, coding and insurance claims, and that’s why doctors have trusted support staff to handle it for them.

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In a survey of more than 2,500 physicians about controlling health care costs, only 36 percent of physicians said doctors had a “major responsibility” for controlling costs. Sixty percent said trial lawyers had a major responsibility, and 59 percent said health insurers did; health systems, patients and drug manufacturers were also chosen by a majority of physicians as having a major responsibility.

Even though about 76 percent of doctors reported being aware of the costs of the tests and treatments they recommend, in practice the actual percentage might not be so high. In a separate study, the physicians and residents of St Luke’s-Roosevelt Hospital in New York City were quizzed about their knowledge of the hospital’s procedure charges, and overall they earned failing grades— less than 25 percent answered correctly.

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For most doctors who responded to the larger survey, however, costs were perceived as largely irrelevant to care. A majority of doctors— 78 percent— said they should be solely devoted to patients’ best interests, even if that is expensive.

‘Emergency room mortality and complication rates are higher on the weekend.’

That’s especially true if you are being admitted with a chronic condition— it may be a riskier to be admitted to the ER on the weekend. “The number of patients who are sick doesn’t go down on Saturdays and Sundays, but the number of health care workers does,” said Dr. Armand Leone, partner and cofounder of Britcher, Leone & Roth, who deals with medical malpractice cases. He is also a board-certified diagnostic radiologist.

Health care workers like their weekends just like the rest of us, Leone pointed out. As a result you end up with on-call workers or newer, less-experienced staff working the off-hours. “These workers aren’t bad at their job, but they don’t know you like your regular medical team does,” he said.

It goes for doctors, too, who usually take turns working weekend hospital shifts, so the chances your doctor is around are slimmer on a Saturday than a Monday.

‘About 1 in 20 cancer diagnoses made in primary care are wrong.’

Errors in medicine are not uncommon, and they span several varieties, from billing errors to surgical errors— all of which can be costly. Researchers from the Houston Veterans Affairs Center for Innovation and Quality analyzed cancer misdiagnoses rates and estimated that about 5 percent of the time, primary care doctors made erroneous diagnoses. This affects about 12 million adults per year, according to the researchers, and about half the time those errors resulted in serious injury.

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The reason why, Leone said, is in heuristics, or the act of making mental shortcuts in a rushed situation. “There is so much pressure for primary care physicians to see a high volume of patients, and they’re not reimbursed for critical thinking time,” Leone said. “When they’re rushed, doctors make diagnoses based on probability, and most of the time they’re correct, but not always.”

If you think your doctor is making decisions in a rushed state, “do something to break that autopilot mode,” Leone said. Ask questions that make the doctor think critically, such as, “If it’s not cancer, what’s the worst it could be?” or “How long do you think until this medication starts to work?”

‘There are safer times to get that elective surgery.’

According to a study last year that included over 55 million patients, the increased risk of mortality following surgery on the weekends is about 2 percent. That’s because similar to emergency room personnel, surgical center workers like to have time off on the weekends. As a result, the surgeon, doctor, nurses and other medical staff who know you well are more likely to be there during the workweek hours.

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If you’re recovering from surgery on a Friday afternoon, you have 60 hours to wait before regular staff gets in. “You want whoever’s coming in tomorrow to know you,” Leone said. “Yes, medicine is a science, but it’s also an art— the art is human interaction. You get a feel for a patient’s needs by just spending more time with them. It’s not just about lab numbers.”