Doctors are well-educated people, but that doesn’t mean they know it all. Good doctors can troubleshoot the human body and direct patients toward better health with empathy and compassion. However, sometimes your physician may be unable to answer your questions, and you need to know when and where to turn for help.

Americans have a healthy amount of skepticism when it comes to their doctors. According to research published in the New England Journal of Medicine, only about 58 percent of American adults believe doctors can be trusted. But distrust across the board may be unhealthy. Knowing which questions your doctor may not be equipped to answer can temper this lack of faith and give you the tools to navigate the health care system accordingly.

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1. What is wrong with me?

Diagnostic errors affect at least one in 20 adults in the country, according to research published last year in the journal BMJ Quality and Safety. The study found misdiagnoses affect some 12 million people, and about half of those errors had the potential to be harmful.

Unfortunately, your doctor may not admit when she just doesn’t know what’s wrong with you. If you are uncomfortable about your diagnosis (or lack thereof), if you don’t feel like your concerns are being adequately addressed or if your doctor is recommending a serious surgery, it may be time to check with someone else.

Don’t be afraid to talk to your doctor about getting a second opinion— the best physicians are often more than happy to refer you to another professional. Plus, when they know you’re going elsewhere, they can be sure that all of your records follow you for the most accurate diagnosis. Also, make sure you double-check with your insurance company that a second opinion will be covered.

2. How much will this cost?

With out-of-pocket costs rising for American patients, expense questions are common, but your doctor likely doesn’t know the answer. Waiting until you’re in the exam room to talk prices isn’t wise because your doctor will probably have to direct you elsewhere. Instead, if you have questions about the cost of any medical treatment or services, ask the billing department for your provider or hospital well in advance.

Medical billing offices are accustomed to providing price estimates to patients. They’ll tell you— and you should take heed— that their estimates are rarely set in stone. Also, insurance coverage can greatly affect how much you’ll pay.

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When you talk to the billing office staff, ask if they’re willing to help you determine how much will be covered by insurance. Many are very helpful in this regard, and because they’re used to navigating health insurance policies and you are not, issues of coverage and your share of the cost will be easier for them to identify. If they don’t have the time or simply aren’t willing, ask for an itemized estimate and call your insurance company next.

3. Will my insurance cover this?

Your doctor may be able to provide some insight into whether a treatment or protocol is “medically necessary,” which is a status insurance companies often require for coverage. But the issue of coverage extends far beyond medical necessity, and your doctor doesn’t know the specifics of your insurance policy.

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It’s up to you to understand your insurance and to ask questions when you don’t. Your doctor’s billing office can be helpful in this regard, but they don’t have the final say— your insurance company does.

Calling your insurer before you go in for an appointment can help clarify whether your visit is covered. If your doctor is proposing a treatment or surgery, and you want to be sure of coverage, ask the billing office how the procedure will be coded when it’s sent to your insurer. Then, call your insurance company with those numerical codes to double-check your coverage, making sure to ask what your cost-sharing responsibilities will be if it is, in fact, covered.

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Several decades ago, the attitude that “doctor knows best” was prevalent. But now, consumers understand the complex and multi-faceted face of health care. Your physician may very well be able to answer many of your questions, but becoming familiar with other sources will help to make you a more empowered patient.