Ask Your Pharmacist

July 29, 2020

Is glucosamine sulfate useful in the treatment of osteoarthritis?


Many New Brunswickers are physically active, whether it be working long hours on the farm, manual labour on the job site, or the normal wear and tear associated with time on the ice, field, or maybe at CrossFit. Eventually, osteoarthritis catches up with many of us (including me, even though I’m still young!).

What is glucosamine sulfate?

Glucosamine sulfate (glucosamine) exists naturally in our body and is a building block for cartilage. The job of cartilage is to provide protection to the ends of bones. When you have osteoarthritis, your cartilage breaks down with wear and tear and leads to pain and sometimes swelling.

Does it work? (and if so at what dose?)

When I was a pharmacy student doing a fourth-year rotation in Tasmania, Australia, I was given the opportunity to present this topic at a state hospital pharmacists’ conference. Almost twenty years later, we now have much more evidence about the effect of glucosamine on joint function, pain, and joint damage caused by osteoarthritis.

Glucosamine may work for people with osteoarthritis of the knee. What does “work” mean? At least two separate studies have shown that when taken at a daily dose 1500 mg (i.e. 500 mg orally three times daily), glucosamine may reduce joint space narrowing in people with mild to moderate knee arthritis. In other words, glucosamine has been shown in two studies to slow the bone-on-bone destruction of the joint seen in osteoarthritis. Two studies also showed a 50 per cent reduction in the incidence of osteoarthritis related surgery of the lower limbs after five years of follow up.

Is it safe?

People who take glucosamine will probably not have significant side effects. At usual doses, glucosamine is well tolerated. Some reported side effects have included nausea, diarrhea or constipation. These side effects can be lessened by taking the pill with food, and by starting at a lower dose and increasing slowly (i.e. 500 mg once daily for one week, then 500 mg twice daily for one week, and 500 mg three times daily as a target dose). Other uncommon side effects are possible. Talk to your pharmacist about your specific side effects, if you experience bothersome symptoms.

When choosing a glucosamine product over-the-counter always choose a product that has a Natural Product Number (NPN) on the label. Products with an NPN have been assessed by Health Canada and found to be safe, effective and of high quality under their recommended conditions of use.   

Early reports suggested that glucosamine may interfere with control of blood sugars in people with diabetes. We now understand more, and glucosamine appears safe to take for people with diabetes. Make sure that you let your pharmacist know if you start taking glucosamine so that he or she can check for potential interactions with your other medication therapy. Some reports have shown that glucosamine may increase bleeding in people who are on warfarin and other blood thinners. Some glucosamine products may originate from shellfish so take care if you have a shellfish allergy.

Even though glucosamine does not require a prescription, it is still medicine. Before you make a decision to take any new medicine, it is very important to talk with your pharmacist to make sure that there are no drug interactions with the medicines you are already taking.  

Can I afford it?

You will find many product combinations containing glucosamine at different dosages and in different dosage forms on the pharmacy shelf. It is not known whether the same benefit exists regardless of the brand of product. This can be confusing, and I encourage you to speak to your pharmacist about which product is best for you. In general, glucosamine regular strength 500 mg tablets cost approximately $15-20 for 60 capsules.  

Bottom Line: Available evidence suggests that consistently taking glucosamine sulfate 500 mg three times daily with food may help slow joint destruction and improve symptoms of osteoarthritis of the knee. Glucosamine is well tolerated and affordable, and may be a suitable alternative for people who are not able to take nonsteroidal anti-inflammatories (i.e. ibuprofen [AdvilR], naproxen [AleveR] to control their osteoarthritis symptoms. Talk to your physician or nurse practitioner about its role in therapy for you. 

Dr Kevin Duplisea (PharmD BSc. Pharm, BSc. ACPR) is a pharmacist at Sharp’s Corner Drugstore in Sussex, New Brunswick. His opinions expressed in this newspaper are published for educational and informational purposes only, and are not intended as a diagnosis, treatment or as a substitute for professional medical advice, diagnosis or treatment. Send your questions to