There is a simple and potentially cost-saving question patients may not know they can ask their pharmacists.

NPR reports that patients “can pay a lower cash price for prescriptions instead of using their insurance and doling out the amount the policy requires.”

But, the pharmacist is often banned from offering this information, so patients have to know to ask.

Pharmacists often operate under a “gag clause” that prevent them from offering this information. According to NPR, in 2013, one in four Part D medications were overpaid for by patient beneficiaries, who had higher copayments than the drug’s list cash prices. For 12 of the 20 most commonly prescribed drugs, patients overpaid by more than 33 percent.

Although pharmacy benefit managers have retorted that such gag clauses are not “typical,” Kala Shankle, a policy and regulatory affairs director for the National Community Pharmacists Association attests to cases where pharmacist are “punished” by insurers for violating terms of gag orders, and are dropped from the network.

Read more here at NPR.