You’ve probably heard the horror stories. You go to a doctor or local hospital and expect that your health insurance will cover your costs. Then you get hit with a huge medical bill, which can leave you on the hook for thousands of dollars.

Such surprise medical bills are all too common because it’s not always clear whether a doctor or medical provider is part of your health insurance network. While your insurance company provides a list of doctors and hospitals that are considered "in-network," there are times when the doctor you want—or need—won't be covered by your insurance. 

This could happen, for example, if you need a specialist and your insurance company doesn't have any doctors with that specialty in its network. According to a 2015 Consumer Reports Survey of 2,200 adults, 11 percent of privately insured Americans tried to receive care from a doctor or facility that was out-of-network in the past two years. 

Harvard analysis last year of 135 plans sold through the federal marketplace found that nearly 15 percent lacked at least one specialist. That was particularly true in the fields of endocrinology, rheumatology, and psychiatry—areas that were most commonly excluded from health insurance networks.  

If you use a doctor that's not part of your network, here’s what you need to do to keep your costs as low as possible.

Call Your Health Insurer

Different types of plans have different rules for going out-of-network, and some will cover a greater share of the bill than others. If you find yourself in this situation, the first thing you should do is call your health insurance company to explain why you need a doctor, says Claire McAndrew, private insurance program director at Families USA. Confirm what type of plan you have and get the most current listing of the providers covered in your plan. Then explain why you are unable to see an in-network provider for the care you need.  

What if you need a doctor in an emergency? All plans must cover emergency care at in-network levels and many insurance plans will include some form of coverage for other types of out-of-network care as well. 

Beyond emergency care, some health insurers do not include out-of-network services at any level. If you find yourself seeking a specialized treatment not covered by your plan, ask if the insurance company can make an exception. You may be able to get the treatment covered if you obtain the necessary approval in advance.  
"Insurers will usually help consumers find in-network providers that meet their needs," says McAndrew. "But if you don't contact them first, they'll be much less likely to hold you harmless for those costs."

You can also call your state insurance department to understand your rights for going out-of-network, McAndrew says. Some states have consumer assistance programs that will advocate for you as well. 

Calculate Your Expected Cost

Ask the doctor you plan to see for the diagnostic code that will be used for billing the health insurance company. If you give that information to the insurance company, you'll get a better estimate of how much you'll end up paying. If you anticipate needing a lab test, ask your insurance company which labs are in your network.  Then you can request that the doctor use those labs when you’re at your appointment. That can save you hundreds of dollars.

Get Help From Your Doctor

Some providers are not covered by insurance at all so you'll have to pay the full fee at the time of service. But ask your doctor for any paperwork that you need to submit to the insurance company. That may improve the chances of getting some of your expense covered. Ideally, the paperwork will include the provider’s name, reason for your visit, the date and description of services provided, and charges incurred. Since the doctor isn't covered by insurance, don't be afraid to negotiate with him, advises McAndrew. The doctor may be willing to charge you less.

Keep Copies of Your Paperwork

No one is going to be a better advocate for insurance reimbursement than you. If the provider you saw wasn’t covered at all but gave you reimbursement paperwork, look for a claim form in the health insurer's online portal that you can fill out and submit along with the paperwork. Then file away copies of everything in case the health insurance company has a question or you need to dispute something later on.  

Even if you take all the necessary precautions, you should realize that you'll have to pay more if you go to a doctor that is out-of-network. One way to reduce the financial burden is to take advantage of a Flexible Savings Account (FSA), if your employer offers one. An FSA allows you to put aside pre-tax funds (up to $2,550 in 2016) to pay for eligible medical expenses like co-pays during the year. You can also try switching to a plan with a broader network of providers during your next open enrollment period.