Having a battery of medical tests may seem like a good idea—like your doctor is leaving no stone unturned in the quest for hidden disease. And getting the right test at the right time can be lifesaving.

But undergoing testing you don’t need is not only a waste of time and money but can also cause harm. “It can expose you to radiation, cause unnecessary anxiety, and lead to expensive follow-up tests and treatments that themselves carry risks, sometimes even more so than the disease you’re screening for,” says Tanveer Mir, M.D., chair of the Board of Regents of the American College of Physicians.

Concerns about over-testing have grown so much that more than 60 groups—including the American College of Physicians, the American Academy of Family Physicians, and the American College of Surgeons, plus Consumer Reports—are now participating in a project called Choosing Wisely to alert patients and their doctors about the risks.

Rates of some tests are going down but more progress is needed, according to a 2015 study in JAMA Internal Medicine. Here are five examples of common tests that are done more often than necessary.

Stress Test for Heart Disease

Why you usually don’t need one: Many people get the test—also called a treadmill or exercise test—as part of their routine checkup. A Consumer Reports survey of people ages 40 to 60 with no history of heart disease or heart-disease symptoms found that almost 10 percent had a stress test within the past five years.

But if you’re at low risk, the tests—which involve having you walk on a treadmill while connected to an electrocardiogram (EKG) to measure your heart health—aren’t recommended. And they can produce misleading results that may require further testing, says Mark Creager, M.D., president of the American Heart Association and director of the Heart and Vascular Center at the Dartmouth Hitchcock Medical Center in Hanover, N.H.

Those follow-up tests can include coronary angiography, which can expose you to a radiation dose equal to 600 to 800 chest X-rays. An exercise stress test costs a few hundred dollars; follow-up tests can add thousands more.

When it’s warranted: An exercise stress test may be necessary if you have symptoms of heart disease, such as chest pain or shortness of breath, or if your doctor determines that you’re at increased risk of a heart attack because of high blood pressure or cholesterol levels, diabetes, smoking, or other risk factors.

Chest X-Rays Before Surgery

Why you usually don’t need one: Many hospitals routinely order presurgery X-rays. But for low-risk patients, those tests find something that requires your surgeon or anesthesiologist to change your care only about 2 percent of the time, according to the 2015 JAMA Internal Medicine study. In most cases, a medical history and physical exam will give your doctors all of the information they need.

“Thirty years ago, hospitals did preop chest X-rays because most surgery patients were under anesthesia for a lengthy amount of time, so doctors wanted to make sure their lungs were healthy,” explains Debra Monticciolo, M.D., a professor of radiology at Texas A&M University Health Sciences and a spokeswoman for the American College of Radiology. “But as procedures have gotten shorter and shorter, they often require conscious sedation. X-rays have become much less necessary.”

Getting an X-ray when you don’t need one could trigger a false alarm that leads to unneeded follow-up tests and delay the care you do need. The amount of radiation in a chest X-ray is small, but the cancer risk from radiation may be cumulative, so it’s wise to avoid exposure when you can.

When it’s warranted: A chest X-ray before surgery is necessary if you have a history of heart or lung disease, or symptoms of those conditions. You should also have a chest X-ray if you’re older than 70 and haven’t had one in the past six months, or if you’re having surgery on your heart, lungs, or any other part of your chest.

CT Scans for Headaches and Concussions

Why you usually don’t need one: If you’re suffering from a bad headache or you hit your head hard, getting a CT scan—which combines multiple X-ray images to create 3D images—may seem to make sense. But the test is often not needed.

In fact, one in three CT scans for minor head injuries, including concussions, aren’t useful, according to a 2015 study. “Concussions can’t be seen on a CT scan,” explains the lead author, Edward Melnick, M.D., an assistant professor of emergency medicine at Yale University.

In addition, one in eight visits to a doctor for a headache or migraine leads to a CT scan or MRI, according to a 2014 study from the University of Michigan’s medical school. But even for people with recurring headaches, only 1 to 3 percent of scans find a significant abnormality.

“Patients come in asking for a brain scan, and physicians are so worried that they’ll miss something that could trigger a lawsuit that they give patients what they want even if there’s no real need,” explains the study’s author, Brian Christopher Callaghan, M.D.

Those scans can spot “incidentalomas”—slightly abnormal results that lead to follow-up tests but ultimately prove to be harmless. And needless CT scans expose you to even more radiation than unnecessary X-rays.

When it’s warranted: In most cases, a neurological exam that includes questions about the injury and symptoms can determine whether you or your child has had a concussion.

Expect a CT scan only after a car crash, a fall from a bike when you’re not wearing a helmet, or another serious accident, or if you have worrisome symptoms, such as confusion, loss of consciousness, weakness or tingling on one side of the body, or loss of hearing or vision.

For headaches, imaging tests may be appropriate if you have unusual symptoms, an abnormal neurological exam, or your doctor can’t diagnose the problem based on your symptoms.

Carotid Artery Ultrasound

Why you usually don’t need one: You may have seen this test offered at a mobile clinic or local health fair. Pitched as a simple, painless way to assess your risk of a stroke, the test checks for clogging in the carotid arteries, which are on either side of your neck. But less than 2 percent of people who have blockages of those arteries, but who don’t have any symptoms, end up having a stroke.

The test doesn’t expose people to radiation, but it often suggests that they have a blockage when in fact they don’t, according to a 2014 review in Annals of Internal Medicine.

“This can lead to further testing and even unnecessary surgery to clear out the arteries, which itself carries risk of stroke,” says Michael LeFevre, M.D., vice chair of family and community medicine at the University of Missouri School of Medicine, and the past chair of the U.S. Preventive Services Task Force, which advises the government on public-health issues. In fact, a common treatment for clogged carotid arteries—carotid endarterectomy—can trigger strokes in 2 to 4 percent of people.

That’s why the task force, as well as the American Heart Association and the American College of Cardiology, don’t recommend ultrasound screening tests for most people.

When it’s warranted: The benefits of the test outweigh the risks if you have a history of stroke or mini-stroke (transient ischemic attack), which is often marked by such symptoms as sudden numbness or weakness on one side of the face or difficulty speaking or understanding.