SPARTA, Mich. (WZZM) -- Carl Langowski uses Lipitor and he's got a lot of company. Lipitor, used to treat high cholesterol,is the number one selling prescription in the country.

Through his insurance plan, Carl pays $8 a month. For Carl, a retired construction worker, that's two meals a day.

He can get a better deal at Meijer, where Lipitor is free. Retail, Lipitor costs $16 for a month's prescription at Costco, and $138 at CVS. (Meijer also offers free antibiotics and free Metphormin, a diabetes drug.)

The price variances are much the same with other common generic drugs, like Actos, Singulair and Plavix.

A 2012 Consumer Reports survey found that retail prices for generic drugs were highest at CVS and lowest at Costco. That's what we found in west Michigan as well.

The best deals, however, were found online, at the site Good RX. It offers deeply discounted coupons redeemable at most major pharmacies.

Good RX brings a transparency and savings to just one part of our health care: prescription prices. To know if you're getting a good deal you need to know what your insurance will require you to pay - a set co-pay, a percent of the full price?

And if you buy outside of your insurer's network, your spending won't count toward meeting your yearly deductible - but with some of the savings that are out there, it may not be worth worrying about that deductible.