(MONEY Magazine) – The last time my wife fainted, which happens once every decade or so, we went to the E.R., stayed for a few hours, found out that she had a concussion and got hit with a bill for $13,086.48. Then it was my turn to faint. It took four months, half a dozen calls and one visit to the hospital to fix the problem (her insurance card hadn't been properly photocopied, so no claim was processed). The result was a revised bill for "only" $1,726.79. Unfortunately, such billing mistakes are all too common. Enter the cavalry: claims-assistance professionals. A relatively new type of consumer advocate, CAPs specialize in helping patients manage billing problems and resolve disputes. Tips from these pros can help ensure you don't get clipped when what you need is care.

Take Preventive Measures

The first rule of billing health: Think like a sick person when you're choosing insurance, advises Dawn Hampton, a CAP and principal of Ph.D. Organizational Services in Santa Barbara. In other words, don't reflexively choose the policy with the lowest premiums, but instead focus on what your out-of-pocket costs might be if you become seriously ill. Look at details like co-insurance, exclusions for medical procedures and caps on costs for expensive treatments, such as chemotherapy, which can top $3,500 a day. That way you won't end up fighting to be reimbursed for a treatment your insurer never actually promised to cover in the first place.

Also, be sure to get all required authorizations before seeing specialists or obtaining second opinions, and make copies for your records. "It's not easy to prove that you tried to get authorizations," says CAP Susan Dressler, owner of Health Claim Assistance in West Chicago. And always use certified mail, return receipt.

Stop the Bleeding

Don't let charges mount by ignoring a big bill you're sure (uh, you hope) is a mistake. Instead, ask health-care providers to stop the collections clock while you gather the necessary paperwork or authorizations. Most will honor requests for a 30-day extension. That will preserve your credit rating while you try to sort out the problem, since many doctors and hospitals now use billing programs that initiate collection proceedings for unpaid bills after 30 to 60 days vs. the previous 90- to 120-day grace period. Warns Hampton: "This is no time to play ostrich."

Try being collaborative, not combative. "The claims of people who get angry right away have a funny way of being misplaced--or at least don't necessarily get an agent's full attention," says Dressler, who spent 17 years working in the claims department of several insurers. Instead, get the full name and direct telephone extension of anyone helping with your claim and make him your ally.

Get Professional Help

If you're unable to make headway in resolving billing problems on your own, bring in a consumer advocate to help you negotiate a fair outcome. You can get free firepower from your state's department of insurance, where representatives offer advice (some specialize in particular health insurers) and may step in on your behalf if they determine that your complaint is valid. To find an office near you, visit the National Association of Insurance Commissioners online (naic.org) or call the help desk at 816-783-8500.

You can also hire help. For fees ranging from $30 to $160 an hour, depending largely on the complexity of your case, a claims-assistance professional can sort through your bills, identify errors, negotiate discounts or settlements, expedite payments and generally keep doctors, hospitals, insurers and collection agencies off your back. For referrals, contact the nonprofit Alliance of Claims Assistance Professionals (claims.org).

Curtis Pesmen is the author of How a Man Ages and The Colon Cancer Survivors' Guide.

85% of hospital bills contain errors, according to AMBR, a medical-bill auditor.