For many consumers, good health care means seeing as many specialists as possible. It may also mean undergoing rounds of tests and, if a serious illness is diagnosed, prolonged hospital stays and extensive treatment.

Though the idea that more health care is better seems to make sense, recent research has shown that none of the above necessarily helps you live better or longer. In fact, too much medical care might shorten your life.

Those findings grew out of the 2008 Dartmouth Atlas of Health Care study and almost three decades of research by John E. Wennberg, M.D., and colleagues at Dartmouth Medical School. Their study of 4,732,448 Medicare patients at thousands of hospitals in the U.S. from 2001 through 2005 found significant variations in the way that people with serious illnesses such as heart failure and cancer were treated during the last two years of their lives. Some regions used two or three times the medical and financial resources than others.

Other Dartmouth research has found that patients with serious conditions who are treated in regions that provide the most aggressive medical care—more tests and procedures, more specialists, and more days in the hospital—don't live longer or enjoy a better quality of life than those who receive more conservative treatment.

Patients treated most aggressively are at increased risk of infections and medical errors that come from uncoordinated care, such as doctors prescribing drugs that duplicate or interact with other drugs. They also tend to receive poorer care, spend a lot more money for co-payments, and are the least satisfied with their health care, the Dartmouth researchers found.

The chronically ill are not the only ones vulnerable to overly aggressive care. Consider the case of a middle-aged IBM executive from the New York City area who experienced chest pain. He went to a cardiologist, who ordered a full workup, including a CT scan of his chest. The scan found no heart problem, but at the edge of the film the radiologist noticed "something funny" in the neck area. A neck surgeon performed a biopsy and found nothing wrong. The cardiologist then performed an angiogram to look for abnormalities in the blood vessels. Complications from that procedure landed the executive in the hospital for a brief period. By the time it was over, his bills were more than $150,000 and he still had no diagnosis. Eventually the pain disappeared on its own.

Months later, when the executive's chest pain returned, he told his medical history to Paul Grundy, M.D., an internist and director of health-care technology and strategic initiatives at IBM's headquarters in Armonk, N.Y. Grundy asked him what he was doing at the time. "Oh, we started gardening again," the man told him. It turned out that overzealous use of his string trimmer had strained a chest muscle, a condition that required no treatment other than an over-the-counter pain reliever. None of the high-priced specialists (some call them the "partialists") had considered muscle strain, a common condition often mistaken for heart pain.

Few Americans are aware of the dangers of this type of unneeded testing and overreliance on specialists. Instead, many fear that their health problems will be neglected or inadequately treated. But for people with good private health insurance or Medicare, the perils of overtreatment are real.

Avoiding excessive testing and hospital stays is easier in some parts of the U.S. than in others where a "do more" medical culture prevails. We worked with the researchers at the Dartmouth Atlas to make their data on 2,878 hospitals available free at ConsumerReportsHealth.org. Use the Web site to find out how hospitals in your area treat people with long-term, life-threatening illnesses. Also consult Hospital Compare to Hospital Compare, a Medicare project that rates hospitals by patient satisfaction and a variety of other measures. And no matter where you live, get the right kind of care for serious illnesses by using these tips.