“For most people, a high-deductible plan is basically a bet against yourself,” said Ms. Stoll. “You’re betting that you won’t get sick and you won’t have an accident. But isn’t that exactly what insurance is supposed to be? A bet that something might happen, and if it does you’ll be protected?”

Whether you are considering a high-deductible policy because you are healthy and don’t think you need much coverage or you want the tax-sheltered savings account or you simply cannot afford anything else, you need to carefully consider the following.

WHY IS THE PREMIUM SO LOW? It is not always simply because the deductible is high. There may be other cost-reducing limitations on the plan as well. If the premium looks too good to be true, look for one of these lurking loopholes:

Image Kathleen Stoll, the director of health policy at the advocacy group Families USA, says high-deductible medical insurance has many potential pitfalls. Credit... Daniel Rosenbaum for The New York Times

A cap on lifetime coverage. It is hard to even estimate what you will need over your lifetime in health care coverage. But when you are looking at this number, keep in mind that the average hospital charge for an appendectomy is $22,000, and the average charge for a hip replacement is $40,000. You do not want a lifetime coverage cap that is going to be exhausted quickly by one or two long hospital stays or by extended outpatient care for a chronic illness.

A cap on doctor visits. Some severely restrictive plans will cover only a handful of doctor visits a year after the deductible is met. Others charge a big co-payment for every doctor visit. Still others will not even start to cover doctors’ visits unless they occur after a hospitalization  which, as Gary Claxton, a vice president at the Kaiser Family Foundation, points out, is basically a hospital-only policy.

A cap on hospitalization costs. Again, consider those hospital costs. Is the policy you are considering going to get you through? Mr. Claxton has seen policies that so severely restrict hospitalization that they will not pay for the first day you are admitted. “That’s the day when you’re most likely to have the most costs,” he said. “Think of it: You’re admitted to the E.R., you have surgery and you spend the night in the I.C.U., and none of it is covered.”

Other high out-of-pocket costs. Just because you have met your deductible doesn’t mean you are done spending money. High co-payments of 20 percent or more on doctors’ visits, prescription drugs and hospitalizations can add up quickly. With some of these policies, Mr. Claxton says, you will pay an extraordinary amount in out-of-pocket costs, sometimes as much as $10,000.