Many people take glucosamine hoping the supplement will help aching knees, hips or other joints. It's for sale at your local pharmacy, health food store and supermarket. But you may be wondering: Is glucosamine safe for me? And does this joint supplement really work?
What Is Glucosamine?
Glucosamine is something your body already makes. The body changes this natural substance into building blocks for the cartilage found in your joints, according to the National Center for Complementary and Integrative Health (NCCIH).
Over-the-counter, it comes in several chemical forms, including glucosamine hydrochloride, N-acetylglucosamine and synthetic forms, as well as in various preparations, such as powders and liquids, but most is sold as glucosamine sulfate in capsules or tablets, according to Michigan Medicine, from the University of Michigan Health System. People take it as a dietary supplement to improve joint health, but most scientific studies say it doesn't help much if at all.
Read more: What Foods Have Glucosamine?
What the Experts Say
Mixed research results indicate that glucosamine may help some people with pain, according to the Mayo Clinic, but in some studies, a placebo was more effective. There's little evidence it will restore joints harmed by arthritis or injury.
Glucosamine is often sold in combination with chondroitin, another substance that occurs naturally in the body's cartilage, according to the NCCIH. There's some evidence that chondroitin may benefit joint structure, but the improvements may be too small for users to notice, according to the NCCIH.
Caution may be warranted before you start spending money on the supplement. A study published in July 2016 in Arthritis & Rheumatology that involved 316 people with knee pain was stopped because those taking the combined supplement — 1,200 milligrams of chondroitin sulfate and 1,500 milligrams of glucosamine sulfate — felt worse than those taking a placebo.
Researchers noted that after the initial six months of the study, people taking the supplements had their pain reduced by 19 percent, but the placebo group's pain scores dropped by 33 percent.
A July 2018 meta-analysis in the Journal of Orthopaedic Surgery and Research involving more than 7,100 people with osteoarthritis of the knee or hip, found that glucosamine showed a significant affect when compare with popping a placebo. However, there was not enough evidence to show that a combination of glucosamine and chondroitin is superior to placebo.
On the plus side, side effects are few, so glucosamine is safe for most people to use, says Michael B. Banffy, MD, who specializes in sports medicine and orthopedics at the Cedars-Sinai Kerlan-Jobe Institute in Los Angeles and is a physician for the city's Rams and Dodgers professional sports teams.
"There really are minimal side effects," he says, adding that it's easier on the body than aspirin and other over-the-counter anti-inflammatory medicines that can irritate the stomach or raise blood pressure.
"The other problem is that (being a supplement) it's not regulated by the FDA," Dr. Banffy says. "You never know how much of the active ingredient you're getting."
The common dosage of glucosamine sulfate, often used in clinical studies and cited on manufacturers' labels, is 1.5 grams a day, taken in a single dose or split into three 500 milligram doses.
If you do decide in favor of these supplements, Dr. Banffy suggests buying them from big, reputable, mainstream brands. The American Academy of Orthopaedic Surgeons notes a study by ConsumerLab.com that showed half of the glucosamine and chondroitin supplements tested did not contain the amounts of these chemicals printed on the labels.
An August 2013 Consumer Reports analysis found that out of 16 brands of combined glucosamine and chondroitin supplements tested by independent laboratories, seven fell short on the amounts of chondroitin while glucosamine amounts were accurate.
Side Effects and Contraindications
Glucosamine is made from shellfish shells or produced in a lab, according to the Mayo Clinic. As a result, it may cause problems for people with a shellfish allergy. It may also worsen asthma.
Taken by mouth, glucosamine or a combination of glucosamine and chondroitin may increase the blood-thinning effect of warfarin (brand name Coumadin). Glucosamine may also change blood sugar levels, a possible problem for people with diabetes or related issues, according to the NCCIH.
The NCCIH suggests that anyone who has a shellfish allergy, has diabetes or is pregnant or nursing talk to their doctor before taking glucosamine or adding any new supplement to their daily regime.
Other possible side effects include nausea, heartburn, diarrhea, constipation, drowsiness, headache and skin reactions, according to the Mayo Clinic, which also says glucosamine taken with acetaminophen (Tylenol) may reduce the effects of both.
Is This an Emergency?
- Michael B. Banffy, MD, orthopedist, Cedars-Sinai Kerlan-Jobe Institute, Los Angeles; team physician, LA Rams, LA Dodgers; and consultant, Loyola Marymount University Athletics
- National Center for Complementary and Integrative Health: "Glucosamine and Chondroitin for Osteoarthritis"
- University of Michigan: Michigan Medicine: "Glucosamine and Chondroitin"
- Mayo Clinic: "Glucosamine"
- Arthritis & Rheumatology: "Combined Treatment With Chondroitin Sulfate and Glucosamine Sulfate Shows No Superiority Over Placebo for Reduction of Joint Pain and Functional Impairment in Patients With Knee Osteoarthritis: A Six‐Month Multicenter, Randomized, Double‐Blind, Placebo‐Controlled Clinical Trial"
- American Academy of Orthopaedic Surgeons: "Glucosamine and Chondroitin Sulfate"
- Consumer Reports: "The Facts About Joint Supplements"
- Journal of Orthopaedic Surgery and Research: "Effectiveness and Safety of Glucosamine an Chondroitin for the Treatment of Osteoarthritis: a Meta-analysis of Randomized Controlled Trials"