Denied claims are fairly common—they happen in about one in seven cases, according to the US Department of Labor. For neurology patients, denials are most frequently related to the cost and number of medications, the number of days patients may stay in a rehabilitation facility, and the number of physical therapy visits.

If your claim is denied at the pharmacy and you're required to pay full price, ask the pharmacist about coupons that can reduce the cost. Or ask your doctor for referrals to foundations that can help cover co-pays. These are often based on income, and you will likely have to share that information.

If you get a letter denying coverage, check to make sure all information about the patient—name, birth date, insurance member number, doctor, date of service—is accurate. Then call the customer service number on the back of your membership card to find out why a claim has been denied. The insurer may be waiting for more detailed information from your doctor. If so, call your doctor and ask him or her to contact the insurer promptly. Your doctor may request payment for any treatment already given; explain to the office that you're waiting for the insurer to resolve a denial.

Don't ignore emails or letters from your insurer. Asking for a review of a denied claim is often allowed for a limited time only. Sometimes the insurance company requests more information from your doctor, and once it's received the insurer may allow the coverage. If you find the communication difficult to handle on your own, ask a trusted friend or relative for help.

If a claim is still denied after the doctor and insurer speak, the doctor can appeal the decision. Insurers expect appeals. Occasionally an insurer will cover an alternative—for instance, a pill instead of an injectable drug. If the injectable is preferred because it's more effective and is administered once or twice a year instead of as a daily pill, your doctor can explain those reasons in the appeal. You may have to continue paying for medication while the appeal is in process.

You also may have to try the drug your insurer will cover. In what is known as a “step edit” or “fail first,” you will be asked to take the drug (or undergo the procedure) the insurer recommends and “fail” one or more times before the insurer will agree to cover your physician's preferred choice. That process can take awhile.

More than 20 states have enacted laws that allow patients to get a preferred treatment sooner. To find out the laws in your state, go to steptherapy.com. If your state doesn't have step edit laws, or your claim is still denied, ask your insurer about other appeals. Insurers are required to send information detailing all avenues of appeal.

As a last step, you can reach out to your state's insurance commissioner. You'll find contact information on the state's government website. All insurance plans are required to have an outside review process when coverage is denied. As you go through the process, keep a record of all calls and correspondence.

If coverage is ultimately denied—or even during the appeal process—you can contact a patient organization related to your condition, such as the National Multiple Sclerosis Society, the American Stroke Association, the Alzheimer's Association, or the Epilepsy Foundation. Staff members can explain denials, file appeals, or point you toward other resources to cover the cost of your care. You can also check the drug company's website for discount coupons.

Mr. Evans is CEO of Texas Neurology, a neurologic medical practice in Dallas, and chair of the American Academy of Neurology Health Policy Subcommittee.