Many of the eight million sign-ups in Obamacare exchanges nationwide already face more limited choices for physicians and hospitals than those in the private insurance market. But with low physician reimbursement rates, the problem could get even worse.

For a typical quick patient visit, Dr. Doug Gerard, a Connecticut internist, told NPR a private insurer would pay $100 while Medicare would pay around $80. But Obamacare plans are more likely to pay closer to $80, which Gerard says is unsustainable for his practice.

“I cannot accept a plan [in which] potentially commercial-type reimbursement rates were now going to be reimbursed at Medicare rates,” Dr. Gerard told NPR. ”You have to maintain a certain mix in private practice between the low reimbursers and the high reimbursers to be able to keep the lights on.”