How long is it safe to take glucosamine sulfate?

Indefinitely: Glucosamine is generally very safe for the long term. It can occasionally cause GI issues. If you are diabetic, watch your glucose level as it may rise on glucosamine.

Glucosamine: Has not been found to be unsafe. Can use as long as you think it is helping.

Long term.: As far as we know, the combination of glucosamine and chondroitin is safe to use in the long term. Studies had people taking it for at least two years.