Filling a prescription is no longer the simple errand you run after a doctor visit.

With drug prices rising and insurance coverage shrinking, it pays to ask questions and do a little research before handing over your insurance card at the pharmacy counter. Having coverage offers no guarantee that you're getting the best price for your medicine.

Customers of CVS and Walgreens brought that concern to light earlier this month when they sued the drugstore chains over prices paid for generic prescriptions. The lawsuits accuse the companies of charging insured patients more for generic drugs than wh...