Those odds are almost exactly in the middle of the pack - a better chance than you'll find in the nation's most populous states, such as New Jersey, but far worse than rural states in the heartland where almost all physicians accept new Medicaid patients.
Medicaid has low reimbursement levels compared with private insurance and the federal Medicare program, which covers seniors and the disabled. This means that doctors don't get paid as much for providing services to Medicaid patients.
That means some primary-care physicians simply won't take on new Medicaid patients or have opted out of Medicaid altogether, which is a concern for public-health advocates.
Nationally, about 64.7 percent of primary-care physicians accept new patients with Medicaid. That's well below the acceptance rate for new patients with private insurance, which is about 81 percent for all physicians, including specialists.
The percentages don't tell the full story, said Cindy Mann, deputy director with the Centers for Medicare & Medicaid Services.
"It's a broader health-care delivery supply question," she said. There's a doctor shortage, and "the ACA gives us some new tools to boost the supply of care providers." Medical care homes, nurse practitioners, and physician assistants will all be a bigger part of the health-care system, she said.
Opponents of the Affordable Care Act and its expanded Medicaid mandate say the percentages prove that paying doctors less, as Medicaid does, won't lead to improved care or wider access; it will instead lead to a round-robin search for physicians willing to be paid about half of what they would make for treating a patient with private insurance.
It could also lead to lesser outcomes for patients, since people on Medicaid have a tougher time finding physicians and scheduling timely appointments than people with private insurance.
In Pennsylvania, about 68 percent of doctors are taking on new Medicaid patients as of 2011, according to a study published in the journal Health Affairs, conducted by Sandra Decker, a National Center for Health Statistics economist.
Pennsylvania's "new" patient acceptance rate is better than the rate in New Jersey (40 percent) but worse than Delaware (78 percent).
Alan Yeasted, Mount Lebanon-based governor of Pennsylvania's American College of Physicians chapter, said the percentages may not reflect an unwillingness by primary-care physicians to take on new Medicaid patients, but rather a general crunch in the physician population, one that could be exacerbated when more people enter the ranks of Medicaid enrollees.
Supporting Yeasted's contention that this is more a shortage issue than a Medicaid issue is recent Pennsylvania Department of Health research, which says 94 percent of "rural" doctors and 84 percent of "urban" doctors currently see Medicaid patients.
That means that nearly all doctors are willing to work within Medicaid and its low rates, but it also means that some physicians already have so many patients that they can't take on any new patients, regardless of whether they have Medicaid, Medicare, or private insurance.
In states with the lowest Medicaid reimbursement rates, though, "you will have difficulty finding a physician who will accept Medicaid in the future," Yeasted said.
He does not include Pennsylvania among those states; here, Medicaid payment rates are about 40 percent lower than Medicare rates for the same services, but that's fairly average, since different states reimburse for Medicaid at different levels.
Several studies, including one published in 2011 by the University of Pennsylvania, suggest that patients with public insurance - especially Medicaid and CHIP (the Children's Health Insurance Program) - "are less likely to receive specialty care" than privately insured patients.
Bill Toland can be reached