Irene Adkins doesn’t know how she’s going to afford the drugs that keep her alive in 2018. The 59-year-old former building supervisor from Falls Church, Va., suffers from pulmonary hypertension, a rare lung disorder that can lead to fatal heart failure if left untreated. To keep the disease at bay she takes a few pills each day that, together, cost about $150,000 per year. While Adkins’s government-funded Medicare plan covers most of the cost, her out-of-pocket portion is about $10,000—a sum she can’t afford on her $1,600-a-month disability check.

Like hundreds of thousands of Medicare patients who can’t afford the copays on astronomically priced drugs, Adkins has turned to help from a fast-growing corner of the convoluted U.S. health system: patient assistance charities, which are funded almost entirely by drugmaker contributions and help Medicare patients with out-of-pocket expenses.

Now that help is in peril. For the past two years federal regulators have issued subpoenas and scrutinized relationships between drug companies and the charities, which are supposed to operate independently from industry donors. In November the U.S. Department of Health and Human Services yanked its approval from one charity, Caring Voice Coalition Inc., which gave $129 million in aid to tens of thousands of patients in 2016. Caring Voice now says it may not be able to help patients next year. It plans to announce its decision about its future in January.