WASHINGTON, D.C. — An estimated 18 million U.S. adults reported in June that they were unable to pay for at least one doctor-prescribed medication for their household during the prior three months, according to a new Gallup survey.

That’s about 7% of American adults, up from the 6% reported in March. However, in that time period, Gallup says the percentage jumped from 10% to 19% among those in households earning less than $24,000 a year, a statistically significant increase.

Gallup says the inability to pay for a prescription runs twice as high for households with an adult younger than 65, compared with households that have at least one senior. That’s despite the fact that prescription drug usage climbs significantly with age.

Gallup also reports that being unable to afford medication over the prior three months climbs with medical need.

“Among respondents with three or more chronic conditions, or eight or more prescriptions, reports of being unable to pay for a prescribed drug in the household reach 11% and 18%, respectively,” wrote Gallup. “Among respondents with no chronic conditions and no more than two prescribed drugs, these household rates drop to 4% and 5%, respectively.”

And the analytics company says respondents with certain chronic conditions are significantly more likely to suffer medication insecurity than adults are generally.

High costs often lead to Americans going without prescribed medications. Gallup says 10% of Americans report skipping dosages in the prior 12 months as a way of saving money.

“This rate is considerably higher among lower-income households. Among respondents in households earning less than $48,000 annually, for example, 18% report that they or someone in their household had skipped a pill,” said Gallup. “Even among higher-income households earning $90,000-$180,000, 7% of respondents report having skipped a pill in the prior 12 months."