What can be more frustrating than getting denied by your health insurer for coverage just when you really need it?

One attorney who deals with these issues, Mala M. Rafik, of Rosenfeld & Rafik, Boston, says knowing the ropes is key.

Ms. Rafik handles cases of chronically ill patients in which health-care costs can run some $200,000 annually.

Medical insurance denials, she says, most frequently come in these two areas that health insurance sales representatives conspicuously omit when they sell your policies.

Insurer "caps" or limits on coverage of certain services. Most health insurance policies have annual dollar caps, for example, on coverage of skilled nursing care; durable medical equipment, such as wheelchairs and ventilators; and occupational therapy.

To be covered, a service must be "medically necessary." It can't just be something you want. Want a private nurse to stay in your home to help you go to the bathroom after surgery? Beware that your insurer may not consider this "medically necessary."

So what can you do if you're sick and need coverage, or if your insurer denies you coverage? Ms. Rafik says a key is not to lose your temper. Contacting the right people, on the other hand, may help produce results.

Resources to help your cause:

Your state insurance department. Often they can help you understand your consumer rights and how state laws may protect you.

An insurance company "ombudsman." Most insurance companies employ ombudsmen specifically to help policyholders decipher coverage and plow through red tape.

An insurance company's "chronic illness case manager." Most insurers employ these, she says, to help organize care and maximize services the insurer will cover. You just need to track them down. Some chronic illness case managers, she says, have even gone so far as to make "benefit exceptions" for individuals.

Nonprofit organizations that specialize in your illness. Find these by searching online. Their employees, used to assisting persons with problems similar to yours, often can help guide you.

Don't just write your insurance company that you disagree with its decision and expect results, she warns. Your coverage depends largely on state and federal laws and the terms of your insurance contract. Here are some of the most effective tactics recently outlined by Ms. Rafik in Elderlawanswers.com.

Request from your insurance company a detailed explanation of its denial, based on the terms of your policy. Have the insurer nail down the specific clause in your policy that applies.

Request in writing from your employer and insurance company a copy of your full policy -- not just the abbreviated synopsis. Read it.

Obtain from your insurer a copy of your "claims file," including the insurer's own medical review.

Write your insurer questioning the denial. If necessary, appeal it under the company's internal appeals process. Call on your doctors and other experts for help.

Consider in advance of the appeal asking your treating physicians to respond in writing to the specific reasons medical reviewers gave for denial.

To help your challenge, question the credentials of the insurer's medical reviewers as they relate to your illness. Find out whether they have spoken with your treating physicians about the care you require. Any holes you can find in their responses may help.

Keep copies of all communications between you and your insurance company. Record dates of correspondence. Note names, dates, times and correct spelling of everyone with whom you speak and their responses.

Don't give up. If necessary, publicize your case in the media. Notify your senators and/or representatives. Contact an attorney.

Ms. Rafik says that even if you must pay the bills, you still might get some relief. Say you have an HMO (health maintenance organization) or PPO (preferred provider organization). Bills for uncovered services often are at much higher rates. You frequently can at least negotiate these down to the rates for covered services.

Also, Ms. Rafik says, providers may agree to waive fees and/or approve a payment plan.