States are plowing billions of dollars into a high-stakes health care experiment that’s exploding around the country: using scarce public health insurance money to provide housing for the poorest and sickest Americans.

California is going the biggest, pumping $12 billion into an ambitious Medicaid initiative largely to help homeless patients find housing, pay for it, and avoid eviction. Arizona is allocating $550 million in Medicaid funding primarily to cover six months of rent for homeless people. Oregon is spending more than $1 billion on services such as emergency rental assistance for patients facing homelessness. Even ruby-red Arkansas will dedicate nearly $100 million partly to house its neediest.

At least 19 states are directing money from Medicaid — the state-federal health insurance program for low-income people — into housing aid and addressing the nation’s growing homelessness epidemic, according to the Centers for Medicare & Medicaid Services. Even though there’s little agreement that this will provide a long-term fix for vulnerable patients’ health or housing, the Biden administration is encouraging other states to jump in. Several are in the pipeline, including Tennessee, West Virginia, and Montana — and New York got the green light from the federal government in January.

Using health care funding to house people is “a big philosophical debate,” said Alex Demyan, assistant director of Arizona’s Medicaid agency. “We know health care can’t solve all the problems, but we also know that housing agencies are maxed out and we have enormous need to help stabilize people.”

Homelessness jumped 12% in the U.S. last year, to an estimated 653,104 Americans, the highest level on record, even as the nation dramatically increased its inventory of permanent housing and temporary shelter beds.