Glucosamine: Benefits and Side Effects

Glucosamine is a natural substance in your body that is used to build cartilage, the flexible connective tissue that supports movement and protects joints and bones. According to some proponents, supplementary glucosamine benefits people with arthritis, multiple sclerosis, age-related joint problems, and many other conditions.

Most supplements are made with marine life shells, such as shrimp and crabs. These supplements may not be appropriate for everyone and should not be combined with certain types of medication.

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

What Is 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.

Benefits of Glucosamine

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

• Osteoarthritis (joint pain and bone health)
• Rheumatoid arthritis (inflammation)
• Type 2 diabetes
• Inflammatory bowel disease (such as ulcerative colitis)
• Temporomandibular joint disorder
• Autoimmune disease (multiple sclerosis, type 1 diabetes)

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.

Osteoarthritis

Glucosamine may offer benefits in treating osteoarthritis (OA), especially in the knee. A 2016 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.

Studies across two decades had found mixed results on glucosamine benefits. However, a 2023 review of 15 studies found glucosamine did relieve pain in people with knee osteoarthritis and was safe to use. The authors note these are short-term effects and call for more study because OA is a chronic condition for which people are treated across a lifetime.

Rheumatoid Arthritis

Rheumatoid arthritis (RA) differs from OA because its underlying cause is an inflammatory process linked to autoimmune dysfunction, although researchers are still working to understand the precise causes. There is likely a genetic factor in many cases.

The research on whether glucosamine can help is mixed. A 2017 study of supplement use in older adults found some pain relief benefit when using glucosamine. On the other hand, a 2022 review of a wide range of supplements and diets found no benefit to glucosamine for RA.

Type 2 Diabetes

Type 2 diabetes is a health condition that develops over time and is typically diagnosed in adults as their body's ability to produce and effectively use insulin affects their blood sugar levels. There are mixed results on whether glucosamine affects blood sugar levels, some suggesting it does and others reporting no adverse effects or risk to glucose metabolism.

Some studies suggest that glucosamine use over time can actually have a protective effect against developing type 2 diabetes. Researchers who followed more than 400,000 people for an average of just over 8 years found that glucosamine use led to a 17% lower risk of developing type 2 diabetes. They also caution that more study is needed, including dosage and other supplement factors.

Temporomandibular Joint Disorder

Glucosamine is possibly effective for temporomandibular joint (TMJ) disorder, but a 2023 review of eight studies found it was not possible to confirm a benefit on the basis of existing evidence.

However, length of time when taking glucosamine (more than three months) did appear to improve mobility, limit pain, and offer anti-inflammatory benefits. The authors call for more study on TMJ.

Inflammatory Bowel Disease

One of the impacts of inflammatory bowel disease (IBD) is that it reduces your body's ability to use certain types of glucosamine. This affects tissue in your digestive system and contributes to IBD symptoms. Some researchers find that glucosamine supplements may reduce IBD symptoms.

A small study of healthy people who took glucosamine suggests it reduced symptoms of bloating with some benefits toward constipation. However, more study is needed to understand glucosamine use and digestive health, including any benefits in reducing the risk of colorectal cancer.

Multiple Sclerosis

Glucosamine benefits are studied in people diagnosed with autoimmune disorders like type 1 diabetes and multiple sclerosis (MS), in which the disease causes the body to attack its own healthy cells.

A specific supplement form called N-acetylglucosamine shows promise in treating MS, with therapy leading to lower levels of inflammation. About 30% of people in one study showed improvement in their neurological disability.

Side Effects of Glucosamine Supplements

Glucosamine side effects are typically mild and include:

• Nausea
• Bloating
• Diarrhea
• Constipation

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. 

Interactions and Warnings for Glucosamine Supplements

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 also 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 Sources 

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, 1,500 milligrams (mg) per day, taken orally either at once, in two doses of 750 mg, or in three doses of 500 mg, is believed to be a safe dose taken for up to three years in adults.

Check with your healthcare provider about other options, including topical creams and injected forms or combinations of drugs that include glucosamine. While the supplement is sold as glucosamine sulfate, glucosamine hydrochloride, and N-acetylglucosamine, most of the research showing benefits has been done on glucosamine sulfate.

Summary

Glucosamine may be of some benefit to people with certain health conditions including diabetes, osteoarthritis, and multiple sclerosis. However, more research is needed to verify these benefits and better understand how they can be used to prevent or treat health conditions.

If you're considering the use of glucosamine, talk to your healthcare provider before starting your supplements. Certain underlying health conditions and medications can create risks when taking glucosamine. You also should discuss the dosage and type of product it will be safe to use.