Firstly, glucosamine is not a prescription medicine. It is a supplement. But it is a very good supplement. Usually starting with Glucosamine is a great place to start. Dosage wise, there is a very wide dosage range which is acceptable depending upon what your dog tolerates. And Glucosamine is safe and has no side effects. So your size pet can take anywhere from from 1000mg up to 2000mg daily very safely so the 750 mg is well within that range. How well it works does seem to be dosage dependent also. So your pet may do better on two of the 750 mg tablets daily. The only side effect could be upset stomach which is very rare when given with food. Always give it with food and I suggest dividing the dose into breakfast and dinner. Remember, that supplements are not regulated by the FDA therefore there is a lot of variability in quality. If your vet does not have a specific brand they recommend, then Jarrow is a good over the counter brand that can be purchased through many online pharmacies. You will need to give the supplement at least a month to see if it will be enough to help your pet. If he is not getting enough relief, then perhaps adequan injections can be added as they complement Glucosamine very well. Good luck and let me know if I can be of further help. I have certification in rehab medicine so I work alot with pain patients. Cheers!