At first glance, the 2015 health plans offered by the Ohio nonprofit insurer CareSource look a lot like the ones it sold this year, in the Affordable Care Act’s first enrollment season.

The monthly premiums are nearly identical, and the deductibles are the same.

But tucked within the plans’ jargon are changes that could markedly affect how much consumers pay for health care. Generic drugs will soon be free, but the cost of expensive specialty medications will increase. Co-payments for visits to primary-care doctors will go down, but those for emergency room trips will be higher.

Millions of people nationwide bought health insurance this year through the federal government’s health insurance exchange, often through the website Healthcare.gov. Now, as they pick plans for next year, they face a complex battery of choices.

They have until Dec. 15 to select a new plan or they’ll be re-enrolled automatically in the one they currently have. Or, if that plan no longer exists, they’ll be enrolled in another product offered by the same insurer, when available. But even if they get the same plan — of the nearly 2,800 health plans offered in 2014, about 1,700 of them will exist in the same form next year — their benefits may not stay the same.