Medi-Cal patients are swamping California emergency rooms in greater numbers than they did before the Affordable Care Act took effect, despite predictions that the health law would ease the burden on ERs.

Emergency room visits by people on Medi-Cal rose 75 percent over five years, from 800,000 in the first quarter of 2012 to 1.4 million in the last quarter of 2016, according to data recently released by the state’s Office of Statewide Health Planning and Development.

The most dramatic increase began roughly around the time the ACA expanded health care benefits in January 2014. More than 5 million Californians have gained coverage under the ACA, either through the expansion of Medi-Cal, California’s version of the Medicaid program for low-income people, or by purchasing health plans from Covered California, the state’s Obamacare insurance exchange.

The architects and proponents of Obamacare had argued that once people got health coverage they would stop going to the ER so much, because they could visit primary care doctors instead. But in reality, people who were uninsured before the ACA were actually reluctant to go to the ER unless they were “about to die,” because they would be saddled with big bills, said state Sen. Richard Pan (D-Sacramento), a pediatrician. Under Medi-Cal, though, patients aren’t worried about those expenses.

And old habits die hard: A newly-insured patient accustomed to visiting the ER for treatment might not immediately switch to a primary care doctor who is, “just a name — not somebody you know,” Pan added.

Still, experts believe fewer Medi-Cal patients would be visiting the ER if there were more doctors willing to treat them.

Though “we have seen a very strong increase in the number of Medi-Cal patients … the number of doctors willing to see Medi-Cal patients has not increased accordingly,” said Jan Emerson-Shea, vice president of external affairs for the California Hospital Association.

Dr. Marc Futernick, the immediate past president of the California American College of Emergency Physicians, agreed that “there aren’t adequate providers for the demands.” He said he believes Medi-Cal’s low payment rates for physicians play a role.

Historically, doctors across the country have been reimbursed less for treating Medicaid patients than those on private insurance or Medicare — especially in California, which ranks 47th in the country in fee-for-service reimbursement rates.

This means the state’s doctors are less likely to accept Medi-Cal patients, who will then seek treatment wherever they can get it, Futernick said. The ER is always open and cannot legally turn people away, even though many of the Medi-Cal patients’ ills could be treated by primary care providers, Emerson-Shea said.

California doctors have long lobbied to increase Medi-Cal reimbursements. They are pushing hard to use some revenue from California’s recently passed tobacco tax to increase Medi-Cal rates. But Gov. Jerry Brown wants to use it more broadly for overall Medi-Cal spending.

Pan, the state senator, noted other factors that could explain the surge in ER use.

Health clinics, which see many Medi-Cal patients, generally cannot provide specialty care on site, he said. “What’s the quickest way to see a specialist? Send them to the emergency room.”

Moreover, many Medi-Cal patients work jobs without flexible hours or sick leave, which means they are not able to make appointments or visit health care providers during regular hours, Pan said.

“When I worked in the emergency room,” he recalled, “people would show up early in the morning with their kids who had an ear infection or cold or something and the parents would tell me, ‘Well, I have to go to work today or I’ll get fired.’”

California is not the only state where the ACA has failed to produce a drop in ER use. A study published in 2014 found that Oregon residents who won Medicaid coverage in a 2008 lottery made 40 percent more trips to the ER in the first 18 months they were covered than those who entered the lottery but were not selected.