“I really try to stay away from the doctor because I am so scared of what everything will cost,” said Ms. Readling, who is divorced and has twin 18-year-old sons. Before every doctor’s visit and test, she asks, “How much are you going to charge me?” She says she tries to arrange “the best deals I can.” But in many cases, the price is still unaffordable, and “I have to do without.”

Even those with insurance have reason to be concerned, economists say, because they end up paying for the uninsured in various ways. Some of the costs are also passed on to taxpayers and employers. To help cover the cost of treating the uninsured, hospitals often increase charges to other patients. Insurers then increase premiums for companies that provide health benefits, and they in turn shift some costs to employees.

Ms. Readling is engaged to be married in June, to another real estate agent. But she said she may postpone the wedding because she would not want her husband to be legally responsible for her medical bills.

“I am scared to get married because I don’t have insurance,” Ms. Readling said. “If I have to go to the hospital and I can’t pay my hospital bills, what happens? Do they go after him? Can they take your home?”

To collect unpaid medical bills, health care providers often obtain judgments against a patient’s spouse, as well as the patient, and file liens against their homes. Ms. Readling says she does not own a house, but her fiancé does.

The idea of universal coverage, in the form proposed by President Bill Clinton, proved politically untenable. Since the Clinton plan collapsed in 1994, the politics of health care have changed because of the steady rise in health costs, the increase in the number of uninsured and the erosion of employer-sponsored insurance. Politicians are once again speaking about universal coverage as a goal, though opinion polls show that many voters still oppose the idea of a government-run health care system.

Ms. Readling said it was stressful enough visiting doctors every few months for her cancer follow-ups. Without coverage, she said, the experience is even more stressful.