WASHINGTON — Ending insurance discrimination against the sick was a central goal of the nation’s health care overhaul, but leading patient groups say that promise is being undermined by new barriers from insurers.

The insurance industry responds that critics are confusing legitimate cost-control with bias. Some state regulators, however, say there’s reason to be concerned about policies that shift costs to patients and narrow their choices of hospitals and doctors.

With open enrollment for 2015 three months away, the Obama administration is being pressed to enforce the Affordable Care Act’s anti-discrimination provisions. Some regulations have been issued; others are pending after more than four years.

More than 300 patient advocacy groups recently wrote Health and Human Services Secretary Sylvia Mathews Burwell to complain about some insurer tactics that “are highly discriminatory against patients with chronic health conditions and may … violate the (law’s) nondiscrimination provisions.”

Among the groups were the AIDS Institute, the American Lung Association, Easter Seals, the Epilepsy Foundation, the Leukemia & Lymphoma Society, the National Alliance on Mental Illness, the National Kidney Foundation and United Cerebral Palsy. All supported the law.

Coverage of expensive drugs tops their concerns.

The advocates also say they are disappointed by how difficult it’s proved for consumers to get a full picture of plans sold on the new insurance exchanges. Digging is often required to learn crucial details such as drugs covered, exact copayments and which doctors and hospitals are in the network.

Washington state’s insurance commissioner, Mike Kreidler, said “there is no question” that discrimination is creeping back. “The question is whether we are catching it or not,” added Kreidler, a Democrat.

Kansas’ commissioner, Sandy Praeger, a Republican, said the jury is out on whether some insurers are back to shunning the sick. Nonetheless, Praeger said the administration needs to take a strong stand.

“They ought to make it very clear that if there is any kind of discrimination against people with chronic conditions, there will be enforcement action,” Praeger said. “The whole goal here was to use the private insurance market to create a system that provides health insurance for all Americans.”

The Obama administration turned down interview requests.

An HHS spokeswoman said the department is preparing a formal response to the advocates and stressed that today’s level of consumer protection is far superior to what existed before President Barack Obama’s law, when an insurance company could use any existing medical condition to deny coverage.

The law also takes away some of the motivation insurers have for chasing healthy patients. Those attracting a healthy population must pay into a pool that will reimburse plans with a higher share of patients with health problems. But that backstop is under attack from congressional Republicans as an insurer “bailout.”

Compounding the uncertainty is that Washington and the states now share responsibility for policing health plans sold to individuals.

Although the federal government is running insurance markets in 36 states, state regulators are still in charge of consumer protection. A few states refuse to enforce any aspect of the law.

Kreidler said the federal government should establish a basic level of protection that states can build on. “We’re kind of piecemealing it right now,” he said.

Much of the concern is about coverage for prescription drugs. Also worrisome are the narrow networks of hospitals and doctors that insurers are using to keep premiums down. Healthy people generally shop for lower premiums, while people with health problems look for access to specialists and the best hospitals.

Before Obama’s overhaul, insurance plans sold on the individual market could exclude prescription coverage. Now the debate is over what’s fair to charge patients.

Some plans are requiring patients to pay 30 percent or more for drugs that go for several thousand dollars a month. HIV drugs, certain cancer medications, and multiple sclerosis drugs are among them.

Although the law sets an overall annual limit on what patients are required to pay, the initial medication cost can be a shock.

California resident Charis Hill has ankylosing spondylitis, a painful, progressive form of spinal arthritis. To manage it, she relies on an expensive medication called Enbrel. When she tried to fill her prescription the pharmacy wanted $2,000, more than she could afford.

“Insurance companies are basically singling out certain conditions by placing some medications on high-cost tiers,” said Hill. That “is pretty blatant discrimination in my mind.”

Hill, a biking advocate from the Sacramento area, has been able to get her medication through the manufacturer’s patient assistance program.

The insurance industry trade group America’s Health Insurance Plans says there’s no discrimination because patients have many options on the insurance exchanges. Gold and platinum plans feature lower cost-sharing, but have higher premiums. Standard silver plans generally require patients to pay a greater share of medical bills, but some have fairly robust drug coverage.

“There are plans on the exchanges that are right for people who have these health conditions,” said Brendan Buck, a spokesman for the group.

For 2015, the administration says it will identify plans that require unusually high patient cost-sharing in states where Washington is running the exchange. Insurers may get an opportunity to make changes. Regulators will collect and analyze data on insurers’ networks.

“People who have high cost health conditions are still having a problem accessing care,” said law professor Timothy Jost of Washington and Lee University in Virginia. “We are in the early stages of trying to figure out what the problems are, and to what extent they are based on insurance company discrimination, or inherent in the structure of the program.”