Many plans offer drug coverage only as an option at extra cost. But under the law, all individual and small-group plans will cover at least one drug in every category and class in the U.S. Pharmacopeia, the official publication of approved medications in this country. Drug costs will also be counted toward out-of-pocket caps on medical expenses.

You go to a hospital emergency room with a sudden and serious condition, such as the symptoms of a heart attack or stroke. The emergency visit is already covered under most plans. But under the reform law, emergency room visits do not require preauthorization, and you cannot be charged extra for an out-of-network visit.

Many plans don’t cover mental or behavioral health services, but that will change under the law. Patients may be billed around $40 per session. In some states, though, coverage may be limited to a set number of therapy visits per year.

Under the law, your insurer must cover your hospitalization, though you may have to pay 20 percent of the bill or more if you haven’t reached your out-of-pocket limit. Some hospitals charge $2,000 a day for room and board alone, and $20,000 with medical services, so those bills can soar. This year, medical costs will help bankrupt 650,000 American households — including many who thought they had decent insurance until diagnosed with a serious illness.

If you are injured or become ill, many plans today cover rehabilitation therapies to relieve pain and help you regain your ability to speak, walk or work. The plans often cover medical equipment, too, including canes, knee braces, walkers and wheelchairs. Few plans, however, address the reform law’s essential requirement for “habilitative” services, which are therapies to help overcome long-term disabilities, such as those that accompany a disease like multiple sclerosis.

Many experts believe this benefit could help rein in the nation’s rising medical costs. The idea is to get people to see doctors and make healthier choices before they get sick and run up medical bills. For example, you may be allowed a free “wellness visit” annually with your doctor to discuss your health. Beyond that, the law instructs insurers to provide all of the 50 preventive services recommended by the U.S. Preventive Services Task Force at no extra cost.

While the law codifies the full set of preventive screening tests — including prostate exams and Pap smears — that individual and small-group insurers must cover, you can still be billed for “diagnostic” tests that doctors order when you have symptoms of disease. Costs can range from $20 for a lab test to 30 percent of a magnetic resonance imaging scan (MRI).

Under the law, children under age 19 will be able to get their teeth cleaned twice a year, as well as receive X-rays, fillings and medically necessary orthodontia. In addition, children under age 19 will be entitled to an eye exam and one pair of glasses or set of contact lenses a year. Relatively few health plans cover children’s dental or vision services today.

The law classifies prenatal care as a preventive service that must be provided at no extra cost. And it requires insurers to cover childbirth as well as the newborn infant’s care. These maternity benefits are a welcome breakthrough for young people, as two-thirds of individual plans have traditionally excluded this type of coverage.