Does Glucosamine Make You Gain Weight? What the Trials Show

No. Glucosamine does not make you gain weight. In the human trials, which followed people for up to three years, weight gain never appeared as a side effect, and side effects on glucosamine were no more common than on placebo.^{1, 2, 3} The idea comes from rats and mice given glucosamine by infusion or in their drinking water at doses hundreds of times higher than any supplement, where it disturbed insulin signalling and, in one 2015 mouse study, increased weight gain.^{4, 5} Glucosamine is a sugar-like molecule, but a day's dose supplies about 6 kcal, and it does not hold water, change appetite or cause weight loss. What moves the scales for people with sore joints is how much they move: pain makes people sit more, and the NHS's first advice for osteoarthritis is exercise and, where needed, weight loss.⁶

• Weight gain: not seen in human trials; the claim traces to rodent studies at very high doses
• Calories: about 6 kcal a day, less than half a teaspoon of sugar
• Bloating and water retention: no evidence; mild digestive upset is the commonest side effect
• Blood sugar: no change in HbA1c or fasting glucose in trials, including in type 2 diabetes

Does glucosamine make you gain weight?

No, and it is worth being precise, because the wrong answer is widely repeated online. Glucosamine has been tested in large, long randomised trials: 1,583 people for six months in the US GAIT trial, and 212 and 202 people for three years in two European trials of glucosamine sulphate.^{1, 2, 3} Those trials recorded every adverse event, and weight gain was not among them: in the three-year trials safety was no different from placebo, and in GAIT adverse events were mild, infrequent and evenly spread across the groups. The Cochrane review of 20 trials put the risk of an adverse reaction on glucosamine at 0.97 times placebo.⁷ If 1,500 mg a day shifted weight, three years of follow-up in 400 people would have shown it.

Where the weight-gain idea comes from

From animals, not people. Glucosamine feeds into the hexosamine pathway, one of the routes a cell uses to sense how much nutrient is around. In the 1990s, researchers infused glucosamine into the bloodstream of rats and produced insulin resistance in their muscles, at concentrations 100 to 200 times higher than oral glucosamine produces in a person.⁴ In 2015, a mouse study gave animals a 10% glucosamine solution as their drinking water: mice on a normal diet gained more weight and body fat than controls, while mice on a high-fat diet gained less.⁵ That paper ranks high for this question, and its first half is where the claim comes from.

It does not transfer to a person taking capsules. The dose is several hundred times higher for body weight, an infusion bypasses the gut and liver that clear most of an oral dose, and when the question was put to people, nothing happened: forty lean and obese adults took standard-dose glucosamine for six weeks in a crossover trial measured with the insulin clamp, and it neither caused insulin resistance nor worsened it.⁸

Can glucosamine cause bloating or water retention?

There is no evidence that glucosamine makes the body hold water. The side effects that do occur are digestive: nausea, heartburn, wind, loose stools or constipation, in a small minority, usually settling when the capsules are taken with food.⁷ Wind can feel like bloating; it is not fluid. Glucosamine sulphate is sold stabilised with a salt, and the crystalline product used in the European trials carries sodium chloride: about 150 mg of sodium a day, roughly 6% of the NHS adult maximum and about what a slice of bread supplies. Most supplements use potassium chloride instead and carry no sodium. Neither amount makes anyone puffy.

Does glucosamine affect blood sugar?

Not at supplement doses, on the trial evidence. In a 90-day randomised trial in people with type 2 diabetes, glucosamine with chondroitin did not change HbA1c, the three-month average of blood glucose, and nobody needed a change to their diabetes treatment.⁹ A 2011 systematic review of eleven human studies called the picture mixed, because a few small studies in people with impaired glucose tolerance recorded a dip in insulin sensitivity; a review the same year of the long-term trials, up to three years and including people with diabetes, concluded that glucosamine has no effect on fasting glucose or insulin sensitivity at any oral dose.^{10, 11} If you have diabetes you can take glucosamine; checking your readings in the first few weeks is sensible.

Does glucosamine affect appetite or cause weight loss?

No to both. No trial has recorded a change in appetite, and glucosamine is not a weight-loss supplement; the mice that gained less on it were obese mice on a high-fat diet drinking a dose no person takes.⁵

What does change your weight when your joints hurt?

Movement, or the lack of it. Knee or hip pain makes people walk less, sit more and avoid stairs, and over a year that is enough to add weight without any change in eating. It runs the other way too: each step puts a multiple of your body weight through the knee, which is why the NHS puts exercise and, for people who are overweight, weight loss at the top of its osteoarthritis treatments.⁶ Exercise that builds the muscles around a sore joint usually eases symptoms rather than worsening them; how can I naturally lubricate my joints covers what movement does for a joint.

What glucosamine does and does not do

Glucosamine is the amino sugar the body uses to build the water-holding molecules in cartilage, taken as a supplement for knee and hip osteoarthritis. The evidence is mixed in a specific way: the 2010 network meta-analysis of ten large trials found an average effect on pain too small to be clinically relevant, while the Cochrane review found that glucosamine sulphate, in the preparation most of the positive trials used at 1,500 mg a day, improved pain and function against placebo, and individual response varies more than the averages suggest.^{7, 12} UK guidance does not recommend it on the NHS, though glucosamine sulphate was a licensed medicine in the UK for knee osteoarthritis; the fair test is to take it daily for three months, judge, and stop if nothing has changed. Glucosamine has no authorised health claim in Great Britain, so what the trials found is reported here as evidence. Vegan glucosamine products often pair the sulphate with a seaweed complex, so anyone with a thyroid condition, and anyone on warfarin, should check with their GP first; is glucosamine bad for you covers who should ask. The Wellgard joint health guide sets out the trials, and what foods are high in glucosamine explains why food is not a practical source.

Frequently asked questions

Does glucosamine chondroitin, or chondroitin on its own, cause weight gain?

No. Chondroitin is a long sugar chain that is barely absorbed. GAIT gave the combination to over 300 people for six months and the diabetes trial above used it for 90 days; neither recorded weight gain.^{1, 9}

What are the symptoms of too much glucosamine?

Digestive upset, and little else. No toxic dose has been established in humans; in animals, very large daily doses for a year caused no adverse effects.⁴

Does glucosamine make you sleepy?

Tiredness and headache are listed among the possible side effects of licensed glucosamine in the UK; in the placebo-controlled trials they were no more frequent than on placebo.⁷ If you feel drowsy after starting it, take it with your evening meal, and stop if it persists.

Does glucosamine cause hair loss?

No trial or case series links glucosamine to hair loss. Shedding is more often about age, thyroid function, iron or a stressful few months; a GP can test for the common causes.

Sources

1. Clegg DO, et al. Glucosamine, chondroitin sulfate, and the two in combination for painful knee osteoarthritis. New England Journal of Medicine, 2006. PubMed 16495392.
2. Reginster JY, et al. Long-term effects of glucosamine sulphate on osteoarthritis progression: a randomised, placebo-controlled clinical trial. Lancet, 2001. PubMed 11214126.
3. Pavelka K, et al. Glucosamine sulfate use and delay of progression of knee osteoarthritis: a 3-year, randomized, placebo-controlled, double-blind study. Archives of Internal Medicine, 2002. PubMed 12374520.
4. Anderson JW, et al. Glucosamine effects in humans: a review of effects on glucose metabolism, side effects, safety considerations and efficacy. Food and Chemical Toxicology, 2005. PubMed 15621331.
5. Hwang JS, et al. Glucosamine enhances body weight gain and reduces insulin response in mice fed chow diet but mitigates obesity, insulin resistance and impaired glucose tolerance in mice fed high-fat diet. Metabolism, 2015. PubMed 25516476.
6. NHS. Osteoarthritis: treatment. nhs.uk/conditions/osteoarthritis/treatment.
7. Towheed TE, et al. Glucosamine therapy for treating osteoarthritis. Cochrane Database of Systematic Reviews, 2005. PubMed 15846645.
8. Muniyappa R, et al. Oral glucosamine for 6 weeks at standard doses does not cause or worsen insulin resistance or endothelial dysfunction in lean or obese subjects. Diabetes, 2006. PubMed 17065354.
9. Scroggie DA, et al. The effect of glucosamine-chondroitin supplementation on glycosylated hemoglobin levels in patients with type 2 diabetes mellitus. Archives of Internal Medicine, 2003. PubMed 12860582.
10. Dostrovsky NR, et al. The effect of glucosamine on glucose metabolism in humans: a systematic review of the literature. Osteoarthritis and Cartilage, 2011. PubMed 21251987.
11. Simon RR, et al. A comprehensive review of oral glucosamine use and effects on glucose metabolism in normal and diabetic individuals. Diabetes/Metabolism Research and Reviews, 2011. PubMed 21218504.
12. Wandel S, et al. Effects of glucosamine, chondroitin, or placebo in patients with osteoarthritis of hip or knee: network meta-analysis. BMJ, 2010. PubMed 20847017.

This article is general information, not medical advice. Joint pain with swelling or heat, or pain after an injury, needs a GP, and if you have diabetes or take warfarin, speak to your GP or pharmacist before starting glucosamine.