With ample opportunities for billing errors within today's complex health care claims and reimbursements systems, it's a wonder people carrying individual medical insurance don't spend more time carefully checking each Explanation of Benefit (EOB). The EOB shows what was charged less what the insurer agreed to cover, the balance being what you owe. Checking your EOB is the first line of defense against overpaying on a health insurance claim.

Your EOB may not reveal a lot, but you can check to see that your name, address, and policy information are correct. You should also confirm that you were charged the "allowable" rate set by your insurer and not a penny more. Deductibles can be as high as $10,000, and payment comes entirely from your bank account, which makes group discounts all the more important.

Other common errors the EOB may reveal include: Failing to get credit for a deductible that has been paid, in-network providers classified as out-of-network, legitimate claims denied as "medically unnecessary," "upcoding" (being charged for more expensive services than you received), and "unbundling" (when a single procedure is broken down and billed as many). At Blue Cross/Blue Shield's Web site www.bcbs.com/betterknowledge/anti-fraud/explanation-of-benefits.html, there's a brief tutorial on how to read and double-check an EOB.

According to a 2001 Harvard study, illness and its associated costs are responsible for 50 percent of all bankruptcies, so it literally pays to request itemized bills from hospitals and other service providers. They are your next line of self-defense against overpayment. The problem is making sense of them, which may require hiring a patient advocate.

Lee Taber works for HealthCare Mediation Group auditing itemized bills, coordinating appeals, and, when possible, negotiating reduced payments and workable payment schedules to keep clients from getting a damaging credit rating. While costly mistakes are rare, Taber estimates that 40 to 50 percent of hospital bills contain errors: "The potential for error is high when a bill is 15 pages long and lists every aspirin and other medical supply."

Advocates receive a percentage of the money they save you. Their cut varies but can run as high as 30 percent. He concisely sums up the benefit of working with an advocate: "If you don't know what you're looking for, how would you find it?"

Indeed, visit the Individual Services page at Medical Billing Advocates of America at www.billadvocates.com/ where you can read about a patient who was charged $12 for a "mucus recovery system" —a box of tissues.

If paying someone to fix a mess you didn't make gets you mad, imagine being the victim of medical identity theft. It's like losing control of your social security number and private financial info, but this is a loss that can be deadly. If a phony claim is made using your benefits, your chart could contain wrong information when you need urgent care. If your benefits are tapped out by an impostor, you'll have none left for your own care. According to a World Privacy Forum report on the crime, all levels of the medical system may be involved, in addition to organized crime.

When it comes to your individual medical insurance, do your homework and prepare in the event of inflated bills or medical identity theft. It can save your money and your life.