WASHINGTON (AP) — "Do you have prescription insurance?"

It's one of the first questions consumers hear at the pharmacy counter, and many hand over their insurance cards in the hopes of getting a good price. But sometimes using insurance can actually cost more — and even prevent the pharmacist from saying so.

That's because of so-called gag rules, which bar pharmacists from telling patients when they could save by paying cash instead of using insurance. The rules — set by companies that manage prescription plans — are getting new scrutiny after President Donald Trump singled them out for critic...