If you’re thinking of leaving your job, Cobra may seem like the one part of our screwy health insurance system that actually works. Named for the health insurance provisions in the 1986 Consolidated Omnibus Budget Reconciliation Act, Cobra ensures that if you leave your job, you won’t also lose your employer-sponsored health insurance. In most cases, you’ll get 18 months coverage on your employer’s plan before you’ve got to come up with other arrangements.

If only it were that simple. It’s distressingly easy to be thrown off of Cobra for no reason at all, and you can count on getting plenty of bad information while you’re trying to get reinstated. Here’s what you need to know to make sure your health insurance coverage continues, even if your job doesn’t.

First, the basics.

Cobra is expensive. In most cases, Cobra allows you to stay on your employer’s health insurance plan. But your employer is no longer going to be paying for it. In 2010, the National Conference of State Legislatures estimated that the cost for Cobra coverage for a family was $13,375.

If, while you were employed, your company deducted $500 a month from your paycheck to cover the cost of health insurance for you and your family, the chances are the company was also paying the insurer about $800 on top of that.

If your company goes belly-up, forget it. This is the really, really bad thing about Cobra. If your former employer goes out of business, you’re not going to be able to go on Cobra, either. Think about it: Cobra lets you stay on your former company’s health insurance policy. If there’s no company, there’s no policy.

Now, the zinger.

You are very likely to be kicked off Cobra. Even if you’ve been paying your premiums.The first time you go to the doctor after going on Cobra, you will probably be told you have no coverage. Don’t freak out. And while it’s probably not a bad idea to check your bank account, those big checks you’ve been writing have most likely cleared. As Diana Mazariegos, the office manager for a busy New Jersey pediatrician’s office, says, “If someone tells me they’re on Cobra, I already know what’s going to happen. I submit the claim, and it gets denied.”

Even once you’re on Cobra, you can be kicked off for no apparent reason. Before going on Cobra, you only had to deal with the insurance company if something went wrong. On Cobra, there’s a third-party administrator to deal with, too. (That’s usually who you’ll be writing your checks to.) While you wrestle with the insurance company, the doctor’s office and the administrator to figure out who’s at fault, you don’t have any insurance. More than half the time, Mazariegos believes, “The Cobra administrator gets paid, but it doesn’t get put through to the insurer.” When my daughter got kicked off Cobra, the representative from ADP (the administrator in my case) said it was because of “a computer glitch,” which is the same explanation Mazariegos says she often receives. ADP did not return a call for comment for this story.

If you’re at the doctor’s office when you find out you have no insurance, they’ll probably give you time to get it sorted. They know this happens. If you find out from the pharmacist — who expects to be paid right away — it’s a much bigger headache.

What can you do to increase the chances this will all go smoothly?

Find out on OneThingNew here.