Doctors have a term for it: “defensive medicine.” It’s when the rash on your hand leads to tests for syphilis–that sort of thing. And it’s a big problem.

Most of us know that the U.S. healthcare system is the most expensive in the world, even though it underperforms many of its less expensive counterparts. What fewer of us know is how much of the cost is due to unnecessary medical testing. PricewaterhouseCoopers’ Health Research Institute has found that “excess tests” are costing the U.S. healthcare system $200 billion a year, roughly 10 percent of what the system spends annually.

According to Miriam Laugesen, a health policy expert and assistant professor at Columbia University’s Mailman School of Public Health, superfluous testing occurs in several incarnations. There is repetitive testing, when a test has already been done elsewhere but the patent’s record is incomplete or missing. There is misplaced testing, when a test intended for one specific population (one susceptible to a rare hereditary condition, for example) gets applied to all patients indiscriminately. There is testing because of patient pressure or fear of being sued.

And then there is testing because of the professional mindset of healthcare providers. John Schumann, a general internist who blogs at GlassHospital.com, notes that modern medicine embraces the idea of using every tool at your disposal. “There’s a culture in American medicine of no stone left unturned,” he says. “Residents are quick to learn they have to have their bases covered. They don’t want to look foolish on rounds.”

This means that most residents–doctors-in-training–at hospitals around the country are ordering a full round of blood tests on every patient in the hospital every morning, even when it’s not clinically necessary. These can cost from $50 to $200 each. Multiplied across every teaching hospital around the country, that figure runs into the billions. Perhaps more importantly, it’s ingraining a culture of over-testing.

It’s not just new doctors ordering tests. “We all do it,” Schumann admits. “And we all look for justifying ordering a test.” To curb over-testing, Schumann thinks doctors need to be incentivized or penalized in their test-ordering. He points to Medicare as a case study of restraint. If a physician can’t offer a good justification for a test, Medicare doesn’t cover it. The system then allows a doctor to reflect on his reasons for ordering a test and either pinpoint a justifying diagnosis or acknowledge that the test is superfluous.

Curbing over-testing is a message that has been resounding lately. Nine medical societies–including the American Board of Internal Medicine–put out a list this month of 45 common tests and procedures that doctors should perform less often. The initiative, Choosing Wisely, asks physicians and patients to limit, among other things, antibiotic prescriptions for sinus distress, cardiac imaging in asymptomatic patients, and imaging for most back pain.

Whether the 374,000 physicians represented by these professional societies will adhere to the guidelines is of course far from certain, and the societies can’t enforce the recommendations, but the message at least is loud and clear. Reinforcing it in the academic world is Steven Weinberger, CEO of the American College of Physicians. In a recent letter published in Annals of Internal Medicine, he called for the emphasis of “stewardship of resources” and “practicing in a cost-conscious fashion.” He says such cost consciousness should even be added as a seventh clinical competency-core medical training guidelines set by the Accreditation Council for Graduate Medical Education. Weinberger’s idea would have doctors trained early on to decrease unnecessary care, saving everyone time, money, and resources.

The money saved isn’t just that of the insurer. Columbia’s Laugesen thinks patients might hesitate to order so many tests if they think more about how large a share of the costs they themselves would have to pay. So the next time you go to the doctor, talk out your options and ask for the doctor’s medical opinion. You could be saving yourself–and everyone else–a lot of money.

Aleszu Bajak is a writer in Buenos Aires.

*Photo courtesy of Lorenzo Sernicola.