Insurance or no insurance, prescription drugs are costing us more than ever. But Tod Marks of Consumer Reports did some digging and found that you can get your meds on discount if you know where to look.

A national price study conducted by Consumer Reports and led by Marks showed just how widely prices can vary on the same drugs in pharmacies throughout the country. The survey found that the prices of four particular prescription drugs can vary by as much as $340, and up to $100 even within individual chains of stores! Of all the drug-store chains, Costco proved to be the cheapest, Marks said.

Opting for generic drugs is the easiest way to save big, but not all drugs have generic counterparts. Prices for medications that are on patent, meaning the pharmaceutical company has control of the market, can still be compared online at sites like DrX.com.

Online drug stores or even the online arms of brick-and-mortar pharmacies like Walgreens and CVS tend to be cheaper, Marks said, because they fill prescriptions from a central repository with cheaper overhead costs.

So next time you take that prescription down to the local drugstore, make sure you've done your homework first.