I take straight Glucosamine (2 1000mg a day). As Mark said, they take a month or so to kick in (some people say 6 wks). And yes, if you run out, you know it.

When my mother was alive, I asked her doctor about using it for her arthritis (she was on about 10 meds) and the doctor said it was perfectly safe to use with her meds.

An acquaintance who has rheumatoid arthritis also uses the straight Glucosamine. She said she used the GC first, then could only get the Glucosamine (she lives way out in the Canadian boondocks), and didn't notice a difference except for price.

I don't know about the GMC combo.

Sue