The cost of health care is making Americans sick with worry.

One in five Americans, 19 percent, report not going to the doctor because they want to avoid paying health-care bills, according to a recent survey from Amino, a San Francisco-based health-care information provider.

A quarter of millennials aged 18 to 35 are forgoing medical treatment to avoid the costs, according to the research.

Three-quarters of the respondents, 74 percent, said their health-care costs have gone up in recent years, and over half of the respondents, 55 percent, said they had received a medical bill they could not afford to pay. While most women, 62 percent, reported having received a bill they could not afford, fewer than half of the men, 47 percent reported the same.

For Amino’s respondents, maintaining good insurance coverage was the most common method used to avoid high health-care costs, named by 39 percent. But almost half of the survey’s insured respondents, 49 percent, said that their provider didn’t provide them with enough information to determine their out-of-pocket costs.

Fewer than one in three respondents, 32 percent, said they were contributing to a health savings account.

In fact, many of the respondents weren’t saving for medical expenses—fewer than half set aside $50 or more per month for their health care, and only 15 percent were setting aside for unexpected health emergencies.

More than one-third of the respondents, 37 percent, said they could not afford an unexpected bill for more than $100 without going into debt.

The research firm Ipsos polled 1,006 U.S. adults for Amino, performing the poll online and surveying those over the age of 18. The poll was conducted from February 23 to February 24, 2017.