When Pam Leonard felt a lump in her breast last November, she hesitated, debating whether to get testing to see whether she had cancer.

She thought of her insurance policy, which carries a deductible of $2,600. She knew she would also have to spend as much as $5,700 on medical bills that would not be covered by an individual policy she bought under the Affordable Care Act. “I went back and forth for a couple of weeks,” Leonard recalled. “It didn’t go away.”

She eventually got a mammogram and ultrasound, confirming a cancer diagnosis.

High-deductible plans have become commonplace, a deterrent used by companies to lower health care costs by discouraging unnecessary tests or treatments. Evidence for that link has mounted since the Great Recession 10 years ago, when deductibles began to soar: People increasingly deferred medical care, putting off elective surgeries and doctors’ visits.

But a recent study of women with insurance plans that carried deductibles of at least $1,000 underscores the danger to consumers required to shoulder a greater share of those costs.

Women who had just learned they had breast cancer were more likely to delay getting care if their deductibles were high, the study showed. A review of several years of medical claims exposed a pattern: Women confronting such immediate expenses put off getting diagnostic imaging and biopsies, postponing treatment.

And they delayed beginning chemotherapy by an average of seven months, said Dr. J. Frank Wharam, a Harvard researcher and one of the authors of the study in the Journal of Clinical Oncology. “Slight delays added up to long delays.”

While the study did not look at how the women fared after treatment, doctors warn that even short gaps between diagnosis and treatment can affect the outcome. Survival rates are higher for patients with some cancers if they are treated early.

“What we see here is an unintended consequence of sharing costs,” said Dr. Ethan Basch, the director of cancer outcomes research at UNC Lineberger Comprehensive Cancer Center.

As an oncologist, Basch said he frequently sees patients making decisions based on financial considerations. If they face high out-of-pocket costs, “they’re of a mind-set to avoid visits, expensive treatments,” he said. “They have a fear.”

At Susan G. Komen, a breast cancer charity, more than half of the questions to its help line are about financial assistance, said Susan Brown, senior director of education and patient support. The organization and its affiliates provide modest grants, including one to Leonard to help pay for a test not covered by her insurance, and refer patients to other resources for aid.

When Leonard tried to talk with the hospital about her medical bills, she found the staff largely unsympathetic. “Because I had insurance, I was told I didn’t need a financial advocate,” she said.

About half of all covered U.S. workers are enrolled in plans with a deductible of at least $1,000, and many must pay several thousand dollars in medical bills before their plans even start to cover their care.

While high-deductible plans are meant to encourage people to think twice about whether a test or treatment is necessary and if it can be done at a lower price, “it’s also frankly to impede their use of these services,” said Dr. Peter Bach, the director of the Center for Health Policy and Outcomes at Memorial Sloan Kettering Cancer Center.

The plans are succeeding in reducing the use of care. “The question is, at what cost?” Bach said.