Obamacare has been successful in meeting one of its main goals: signing up millions of uninsured people for health insurance.

But behind the curtain, there have been some surprising cost increases that champions of Obamacare may not have anticipated.

Senior Reporter Charles Ornstein has been writing about these costs for ProPublica.

“I think that a lot of folks base their decisions about which plans to choose on premiums, which is the sticker price. It’s the first number that you’re drawn to,” he said. But, he warns there’s much more to factor in — like the cost of deductibles, out-of-pocket expenses, and shifting prescription prices.

This summer, Ornstein discovered the co-payment for a generic prescription for his son had doubled in price. He said under health exchange plans, it’s important to take a look at the formulary — the list of drugs covered — and whether that’s changing in 2015. He also explained that insurance companies are placing drugs in different tiers, which can also affect price.

“It’s really important to take the drugs that you know you’re going to take and look them up online for each of the health plans you’re considering to see what your out-of-pocket expenses would be for those,” he said.

In this interview, Ornstein talks to WNYC’s Soterios Johnson about some of the rising costs of healthcare under the Affordable Care Act.