Glucosamine can cause digestive upsets, absolutely. It's one of the known side effects. I've also read that it can hinder normal blood clotting.

I'm curious, what type of supplements do you use?

My St. Bernard is on the Move-Free which my vet recommended. I buy it at Costco. He's been on it for 3 years now. I didn't know glucosamine/msm supplements could cause digestive upsets. So far my boy has been doing okay.

i've been using Flavocin for just over a year now. my dane girl is 8 years old, got her from rescue in august '08. it seems to have become somewhat ineffective so i called my vet a couple of days ago and he suggested i try her on Previcox so i picked some up yesterday. we'll see how she does.

I've been using Petco's Joint Support III for the last year and it has worked great. It not only has the glucosamine chondroitin but also msm and Hyaluronic Acid. No tummy upset seen with this one. Also another note, fish oil is a great supp to add with arthritis. My ridgeback used to have quite a bit of trouble before I started this combination and now she shows no signs of arthritic problems.