Glucosamine: Benefits and Side Effects

Glucosamine is a compound found naturally in the body. It's needed to form and repair cartilage and other body tissues.

Since glucosamine production slows with age, some people use glucosamine supplements to fight aging-related health conditions, such as osteoarthritis. Most supplements are made with marine-life shells, such as shrimp and crabs.

This article explains how glucosamine works, and its benefits and side effects. It also covers what to look for when choosing a glucosamine supplement.

Why Take Glucosamine?

Glucosamine is thought to keep osteoarthritis in check by restoring the body's glucosamine supply and repairing damaged cartilage.

Glucosamine products include:

• Glucosamine sulfate
• Glucosamine hydrochloride
• N-acetyl-glucosamine

Glucosamine is often combined with chondroitin sulfate, a molecule naturally present in cartilage. Chondroitin gives cartilage elasticity and is believed to prevent the destruction of cartilage by enzymes.

In some cases, glucosamine is also combined with methylsulfonylmethane (MSM) in nutritional supplements.

Glucosamine Uses

When used in alternative medicine, proponents claim that glucosamine may help with the following health problems:

• Diabetes
• High cholesterol
• Inflammation
• Inflammatory bowel disease (such as ulcerative colitis)
• Osteoarthritis
• Rheumatoid arthritis
• Temporomandibular joint disorder

Health Benefits

Glucosamine has been widely studied with inconclusive results. It may offer health benefits including a reduction in pain, although a 2018 review published in the journal Orthopedics suggests the benefits may be due to a placebo effect.

Here's a look at other key studies on glucosamine and their findings.

Osteoarthritis

Glucosamine may offer benefits in treating osteoarthritis, especially in the knee. An early report concluded that some preparations of glucosamine may reduce pain and improve function. The study analyzed 20 randomized controlled studies involving a total of 2,570 adults.

Despite some very positive findings, though, there is mixed evidence on these claims. One of the largest glucosamine studies, sponsored by the National Institutes of Health (NIH), questioned these results.

The two-year Glucosamine/Chondroitin Arthritis Intervention Trial (GAIT), compared the effectiveness of glucosamine and chondroitin in 662 people with knee osteoarthritis and concluded that neither showed any benefit in relieving knee pain.

Later studies provide no clearer evidence of benefit. However, some researchers still contend that glucosamine not only helps to ease arthritis pain but also prevents cartilage loss.

A separate six-year study found that cartilage loss appeared to be slowed in adults with knee osteoarthritis who had taken glucosamine and chondroitin for up to six years. The benefits appeared to be greater the longer the supplements were taken.

Further research is needed to make sense of these contradictions.

TMJ

Glucosamine is possibly effective for temporomandibular joint (TMJ) osteoarthritis, according to a small study published in the Journal of Reseach in Pharmacy Practice. The trial involved 60 adults with TMJ who were given either glucosamine, ibuprofen, or a placebo for 90 days.

Although glucosamine and ibuprofen were both more effective in relieving pain than a placebo, ibuprofen proved superior to glucosamine.

Low Back Pain

Glucosamine may not benefit people with chronic lower back pain and degenerative lumbar osteoarthritis, according to previous studies.

However, a 2019 study from Japan reported improved function in people with lower back pain and knee pain who took glucosamine with milk-fat globule membrane (MFGM).

Possible Side Effects

Glucosamine side effects are typically mild and include:

• Nausea
• Heartburn
• Diarrhea
• Constipation

More serious side effects, including drowsiness, skin reactions, and headache, are rare. Taking the supplements with food seems to ease side effects.

People with certain health conditions should not take glucosamine supplements without consulting a healthcare provider. These diseases and disorders include:

• Asthma
• Diabetes
• Glaucoma
• High cholesterol
• High blood pressure

Women who are pregnant or breastfeeding should not take glucosamine as there is not enough research to support its safe use. 

Stop taking glucosamine at least two weeks prior to scheduled surgery, as it may impact the body’s ability to regulate blood sugar. 

Glucosamine Drug Interactions

Glucosamine supplements should not be taken with the blood-thinning drug Coumadin (warfarin) as it may increase its effects and cause bruising and serious bleeding.

There is some evidence to suggest glucosamine may interfere with certain cancer drugs, known as topoisomerase II inhibitors. These include:

• Adriamycin (doxorubicin)
• VePesid (etoposide)
• Vumon (teniposide)
• Novantrone (mitoxantrone)
• Cerubidine (daunorubicin)

Glucosamine may hinder the effectiveness of these drugs.

Dosage and Preparation 

There is no standard recommended dose for glucosamine. The supplement is typically sold in tablets and capsules, and is often included with other supplements that may be effective for pain.

It is OK to take glucosamine every day, but check with your healthcare provider. For example, with osteoarthritis, the following doses have been studied:

• By mouth: 1,500 milligrams (mg) per day, taken either at once, in two doses of 750 mg, or in three doses of 500 mg
• Topically: A cream containing 30 mg/gram of glucosamine sulfate, 50 mg/gram of chondroitin sulfate, 140 mg/gram of chondroitin sulfate, 32 mg/gram of camphor, and 9 mg/gram of peppermint oil has been applied to the skin as needed for 8 weeks.
• By injection: 400 mg of glucosamine sulfate injected into the muscle twice weekly for 6 weeks

What to Look For 

When selecting a brand of supplements, look for products that have been certified by Consumer Labs, The U.S. Pharmacopeial Convention, or NSF International. 

While the supplement is sold as glucosamine sulfate, glucosamine hydrochloride, and N-acetyl-glucosamine, most of the research showing benefits has been done on glucosamine sulfate.

A Word From Verywell

Glucosamine may be of some benefit to people with osteoarthritis. Some healthcare providers may suggest it on a trial basis. If you're considering the use of glucosamine in the treatment of any condition, talk to your healthcare provider before starting your supplement regimen.