It is well known, by now, that almost 50 million Americans lacked health insurance for all or part of last year. What is less well known is that 25 million Americans who did have health insurance often found it pitifully inadequate when a medical crisis hit. They were only marginally better off than those who had no coverage at all.

That is the disturbing finding of a survey by the Commonwealth Fund, a private foundation specializing in health policy research, that was published by the journal Health Affairs. The survey found that some 22 million adults with health coverage all year still spent a large chunk of their incomes — at least 10 percent for middle-class families — for out-of-pocket medical expenses. Another 3.4 million were saddled with high deductibles that would cause financial problems if they became ill.

Conservative health theorists and insurance industry leaders have long argued that the best way to slow soaring health care costs is to force people to pay a significant share of the bill so that they will buy medical services more judiciously, and sparingly. But as out-of-pocket expenses and deductibles have risen, many families are instead postponing or forgoing treatment.

Many of those surveyed had put off seeing a doctor when sick, failed to fill prescriptions or skipped tests, treatments and preventive care. About half had difficulty paying their bills; many took out loans, mortgages or credit card debt to pay them.

Middle-income families have increasingly been hit hard. The rates of underinsurance among families earning more than $40,000 a year nearly tripled from 2003 to 2007. Most worked for small businesses with poor coverage or had to buy costly, bare-bones individual policies on the private market. A typical family might have to cope with rising premiums, high deductibles, benefit limits that exclude or cap treatments and substantial co-payments for each service.

Cutting health care costs and reducing the number of uninsured Americans are critical priorities for this country. But the health care debate needs a wider focus to also address the plight of the underinsured. Insurance plans that discourage needed care will only cause greater sickness and higher costs down the road.