ACA Deadline Day

Narendra Parmar sits with Certified Enrollment Specialist, Laquanda Jordan, as he finishes the process of picking and signing up for health insurance through the Affordable Care act at a Miami Enrollment Assistance Center on December 23, 2013 in Miami, Florida. Today is the deadline for people to enroll in a plan that would start January 1st. (Joe Raedle / Getty Images / December 21, 2013)

Nearly four years after it was signed and after months of uncertainty, President Barack Obama's landmark bid to guarantee Americans health security takes full effect Wednesday when the Affordable Care Act begins delivering health coverage to millions of the nation's uninsured.

How the law will ultimately work and whether it can endure remain unclear, though the fact that coverage will now be real for several million people will almost certainly change the debate over Republican efforts to repeal it.

While that broader political debate plays out, doctors, hospitals and pharmacies across the state and country are bracing for more confusion as patients struggle to understand their new coverage.

Some likely will show up at physicians' offices without insurance cards, the victims of the error-plagued enrollment process that bedeviled the rollout of Maryland's exchange website and the federal starting Oct. 1.

Others may discover that although they're properly enrolled in a health plan, the doctor or hospital they visit or the prescription they want to fill at the local drug store won't be covered by the plan they have selected.

Still other patients, including many who have never had insurance before, may be shocked to learn they have to pay thousands of dollars out of pocket before their coverage kicks in. Like employer-provided health plans, many insurance plans set up under the health law come with low premiums but high deductibles.

Surveys indicate that many Americans have little understanding of basic insurance concepts such as copays and deductibles.

"We still have a lot of education to do for the average man on the street who doesn't really understand the Affordable Care Act," said J. Mario Molina, chief executive of Molina Healthcare Inc., a California-based insurer that is selling policies in nine states.

Dr. Mark Lamos, president and medical director of Greater Baltimore Medical Associates and internal medicine physician at Greater Baltimore Medical Center in Towson, predicts people won't know what their plans cover.

"I think the misunderstanding will be great," Lamos said.

Kaiser Permanente of the Mid-Atlantic States, which is selling plans on Maryland's exchange, said it has increased staffing at its call center and will reach out to new members through telephone calls and welcome kits mailed to their homes. The kits include information about Kaiser's health care system and the many ways people can access it, including online and mobile.

Kaiser also is trying to ensure members get identification cards before January, but said as long as patients are in the computer system they can get care without one.

CareFirst BlueCross BlueShield said members can access their medical ID cards online or through the insurer's mobile app. Members don't have to wait to get the ID card in the mail.

Jeff Goldman, vice president for coverage policy at the American Hospital Association, said most hospitals already have systems in place to help patients sort out their insurance, something consumers often struggle with, particularly at the beginning of the year. "We are pretty confident that people are prepared," he said.

Mary Lynn Carver, a spokeswoman for the University of Maryland Medical System, said hospitals have been helping explain to patients the ins and outs of their insurance plans for years and they will use the same strategies with the newly insured.

"This is yet another service that hospitals have to staff for that is not reimbursed," Carver said.

The issues created by high-deductible and high-copay plans also is nothing new, Carver added. Hospitals are facing increasing levels of bad debt as patients are not prepared to pay these charges, she said.

About 1.1 million people have signed up for new health plans using the federal government's health exchange website.

A late-December surge in sign-ups — combined with rising enrollment on similar marketplaces operated by 14 states and the District of Columbia — means that about 2 million people nationwide appear to have signed up for health coverage since Oct. 1.

Not all states have reported their enrollment numbers through Dec. 24, so an exact tally is not available.