N-Acetyl D-Glucosamine

Glucosamine has been on shelves for decades and the evidence still hasn't settled. These are the questions our naturopaths ask in store.

A good fit if

• You have ongoing knee discomfort and you'll give it a few months
• You want glucosamine sulfate specifically, which is the form with the encouraging evidence
• You avoid shellfish and want the corn-fermented version
• You'd rather understand mixed evidence than be sold a certainty

Check with us first if

• You have asthma. It's named as a group to take care, alongside shellfish allergy.
• You take warfarin. Caution is advised, although one review found no significant interaction.
• You take diabetes medicine. Caution is advised, although the trial evidence was reassuring.
• You have kidney disease or take heart or blood pressure medicine, and the product is the potassium chloride form.
• You're pregnant or breastfeeding. There's no warning on Australia's permitted ingredients list, but there's no safety information either.

• Glucosamine sulfate (item 2368). Best known for: The salt used in the long-term trials. Absorption: Allowed in listed medicines with no conditions. Typical use: The form to choose if you are following the evidence that favours glucosamine.
• Glucosamine sulfate potassium chloride (item 2369). Best known for: A stabilised sulfate salt, very common on the shelf. Absorption: Potassium chloride is a required part of it. Typical use: Must carry a kidney and heart warning, and has a 550 mg potassium limit when taken by mouth.
• Glucosamine sulfate sodium chloride (item 2370). Best known for: The version stabilised with sodium. Absorption: Allowed in listed medicines with no conditions. Typical use: An alternative if potassium is a concern for you.
• Glucosamine hydrochloride. Best known for: A different salt with different evidence behind it. Absorption: The sulfate evidence does not carry over to it. Typical use: Check which salt a product actually uses.
• Corn-fermented glucosamine. Best known for: Made without crustacean shell. Absorption: The way around the shellfish question. Typical use: The option if an allergy or a vegetarian diet rules out glucosamine made from shellfish.

Reference values. There's no recommended intake for glucosamine, because it isn't a nutrient.

Typical supplemental range. Australian labels usually suggest around 1,500 mg a day, the dose most trials used, taken in one go or split. The long-term trials ran for one to four years, and the highest dose used in a human trial we reviewed was 3,000 mg a day of corn-fermented glucosamine.

Upper level. Australia's permitted ingredients list (Schedule 1) sets no upper limit for any form of glucosamine, and the NHMRC has no reference value for it. The one firm number applies to glucosamine sulfate potassium chloride: taken by mouth, it's only allowed in medicines containing less than 550 mg of potassium chloride.

Worth knowing. If you're going to try it, give it months rather than weeks. The trials that found an effect ran for a year or longer. What you need depends on your age, diet and health, so talk to one of our naturopaths.

Food first, where the diet allows it.

• None meaningful: glucosamine isn't obtained in useful amounts from food; supplements are manufactured

If any of these sound like you, talk to one of our naturopaths or your doctor before you start.

• You have a shellfish allergy. Most glucosamine is made from crustacean shell. Of 366 Australian side-effect reports on glucosamine and chondroitin products between 2000 and 2011, 263 (71.85%) were allergic-type (hypersensitivity) reactions.
• You have asthma. It is named alongside shellfish allergy as a group that needs caution.
• You take warfarin. Caution is advised, though the same review found no significant interaction. The evidence is not settled.
• You take diabetes medicines. This is named as a group needing caution, though 90 days of glucosamine hydrochloride with chondroitin was reassuring for blood sugar control.
• You have kidney disease, or take heart or blood pressure medicines. Glucosamine sulfate potassium chloride (item 2369) must carry a Schedule 1 warning about this.
• Pregnancy and breastfeeding. No glucosamine item in Schedule 1 carries a warning, but we found no safety data either.
• Children. Glucosamine items have no children's restriction, but sodium chondroitin sulfate (item 4582) must be labelled "Adults only", and joint health claims often carry age limits.
• Products that are not pharmaceutical grade. Safety monitoring after sale lists side effects specifically for non-pharmaceutical-grade glucosamine and chondroitin.
• If you take prescription medicines, check with your doctor, pharmacist or our naturopaths before you start.