I am 100% certain CVS can bill Part B for insulin. Like Walgreens the staff at your location may not know how. People have mentioned having more success at the embedded CVS locations, Target might be the most common and sometimes having to go to a store farther away.
Just in case there are other reasons CVS is a terrible option for you and you want to give the kids at your local Wags one more chance here is almost everything they need to do.
