Your doctor is recommending a surgical procedure you're unsure about. Or maybe you've just received a diagnosis you don't understand. Or perhaps your doctor isn't giving you any diagnosis at all and you still don't feel right. In all these situations, you should seek a second opinion from another physician. That's a message most Americans don't seem to get. According to a 2005 Gallup poll, about half of 5,000 Americans surveyed said they never seek a second opinion when their doctor "diagnoses a condition, or prescribes a treatment, drug, or operation" while just 3 percent say they always seek one.

What's the problem? In most cases, it's ignorance of how the health-care system works. Patients just don't understand that doctors think seeking a second opinion is routine. Many insurers recommend it and some even require it for certain procedures. But women in particular often say they feel awkward about consulting another doctor because they worry that their primary physician will be less than cordial in future visits. In fact, that's rarely the case. "I think the physician benefits almost as much as the patient from having a second opinion," says Dr. Charles Cummings, executive medical director of Johns Hopkins Medicine International. "It is always a good idea to get another set of eyes looking at the slides, looking at the lab data … to structure a diagnostic and treatment plan."

Doctors say that both men and women should seek a second opinion in virtually all types of non-emergency surgery, when your doctor recommends long-term medication that has potential side effects and if you are not feeling better despite repeated visits to your doctor. In the first two cases, studies indicate that the second physician is most likely to confirm the initial recommendation, but may also suggest alternatives for you to consider. In the last case, "another set of eyes," especially if they belong to a specialist, may catch something your first doctor missed.

In addition to these general recommendations, women should get a second opinion for certain issues specific to gender. That's especially true if you a get a recommendation for a hysterectomy, an operation in which the uterus is removed. It's the second most common surgery among American women (more than 600,000 are performed annually). And yet, many doctors think there are other ways to deal with some of the problems—such as uterine fibroids, pain or heavy bleeding—that lead to hysterectomies. Those other options might include medication or less drastic procedures. "I see women on a weekly basis who are not given choices," says Dr. Holly Thacker, director of the Center for Specialized Women's Health at the Cleveland Clinic. "A woman should be suspicious if she's not given choices. That should be the first red flag."

Women should also seek a second opinion for unresolved cardiac problems. "Many women who present with the same risk factors as men do not get the same treatment," Thacker says. Until recently, for example, doctors didn't understand that the signs of a heart attack in women can be very different from those in men. (Some of those signs include shortness of breath, weakness and unusual fatigue, which are much subtler than the acute chest discomfort you see in heart attacks in the movies.) Tests given to detect heart disease in men may not always be sensitive to women's heart problems so if you get an all-clear but continue to experience symptoms such as shortness of breath or periods of rapid heartbeat, you should seek another opinion—preferably from a specialist in women's heart disease.

If you get a diagnosis of any kind of cancer, especially breast or gynecological cancer, you should also seek a consultation. Although there is widespread agreement on the effectiveness of many therapies, it's a good idea to talk to another physician who can suggest alternatives. Women who are told that they have a condition considered a precursor to breast cancer may also want a second opinion. This is often a controversial area with some doctors urging much more aggressive action than others. You will need to understand how these issues apply to your particular situation.