When I worked at a supplement store during college, people would frequently purchase glucosamine supplements to prevent or lessen joint pain.

Due to its popularity, I assumed glucosamine was a safe and effective supplement for joint health.

However, I’ve since learned that the evidence to support glucosamine for joint health and its other supposed health benefits isn’t as clear-cut as the manufacturers would lead you to believe.

This article explains everything you need to know about glucosamine, including its benefits, side effects, and dosage information.

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Glucosamine is a compound that occurs naturally in your body. Chemically, it’s classified as an amino sugar (1).

It serves as a building block for a variety of functional molecules in your body. It’s primarily recognized for its role in developing and maintaining the cartilage within your joints (1).

Glucosamine is also found in some animal and other nonhuman tissues, including shellfish shells, animal bones, and fungi. Supplemental forms of glucosamine are often made from these natural sources (2).

This supplement is frequently used to treat and prevent joint disorders like osteoarthritis. You may take it orally or apply it topically via a cream or salve (3).

Summary

Glucosamine is a chemical compound that occurs naturally in both human and animal tissues. In humans, it helps form cartilage and is commonly used as a dietary supplement to treat joint disorders like osteoarthritis.

Glucosamine is often used as a supplement to treat symptoms of various inflammatory conditions.

Though glucosamine’s mechanisms are still poorly understood, it appears to readily reduce inflammation.

In a small study in 18 adults with overweight, taking 1,500 mg of glucosamine hydrochloride plus 1,200 mg of chondroitin sulfate daily for 28 days lowered C-reactive protein (CRP) — a biomarker of systematic inflammation — by 23% compared with placebo (4).

Like most other research on glucosamine, this study simultaneously supplemented with chondroitin, a compound similar to glucosamine. It’s also involved in your body’s production and maintenance of healthy cartilage.

Although glucosamine and chondroitin have been shown to lower systematic inflammation, it’s unknown whether they have any localized anti-inflammatory effects.

That being said, glucosamine and chondroitin have been shown to inhibit the activation of inflammatory pathways in human synovial cells. These cells are responsible for producing synovial fluid components, or joint fluid (5).

Interestingly, glucosamine’s anti-inflammatory effects have also has been associated with a lower risk of developing conditions mediated by inflammation, like type 2 diabetes (6).

Still, more research is needed to better understand how glucosamine may help reduce inflammation in your body.

Summary

Some research indicates that glucosamine may reduce inflammation, especially when used alongside chondroitin supplements. Still, more research is needed on the topic.

Glucosamine exists naturally in your body (1).

One of its main roles is to support the healthy development of articular cartilage, a type of smooth white tissue that covers the ends of your bones where they meet to form joints (7).

Along with the lubricating liquid called synovial fluid, articular cartilage minimizes friction and allows bones to move freely and painlessly across one another.

More specifically, it is thought that glucosamine promotes the creation of certain chemical compounds, including collagen, that are important structural components of articular cartilage and synovial fluid.

Some studies indicate that taking glucosamine supplements may protect joint tissue by preventing the breakdown of cartilage, particularly in athletes.

For example, one study demonstrated that taking 1.5–3 grams of glucosamine daily for 3 months significantly decreased cartilage breakdown in collegiate soccer players and professional rugby players (8).

These results suggest a joint-protective effect of glucosamine. However, more research is needed.

Summary

Glucosamine helps develop tissues that are crucial for proper joint function. While more studies are necessary, some research indicates that glucosamine supplements may protect your joints from damage.

Glucosamine supplements are frequently taken to treat various bone and joint conditions. Most scientific research on glucosamine has focused on the use of one specific form called glucosamine sulfate.

This molecule has been well-studied for its potential to treat symptoms and disease progression associated with osteoarthritis (OA), rheumatoid arthritis (RA), and osteoporosis.

Multiple studies indicate that taking daily glucosamine sulfate supplements may offer effective, long-term treatment for OA by significantly reducing pain, helping maintain joint space, and slowing disease progression (9, 10, 11, 12).

Meanwhile, other studies have not found glucosamine to significantly improve joint pain or function in people with hand, hip, or knee osteoarthritis (13, 14, 15, 16).

Based on the conflicting evidence, some scientific organizations recommend against the use of glucosamine for managing knee osteoarthritis (17).

As such, more human research is needed to better understand the mechanisms of and best applications for glucosamine in joint and bone diseases.

Summary

Though glucosamine is used frequently to treat various bone and joint conditions, more research on its effects is needed.

People often use glucosamine to treat a wide variety of chronic inflammatory diseases, although scientific data to support this is limited.

Interstitial cystitis

Glucosamine is widely promoted as a treatment for interstitial cystitis (IC), a condition characterized by chronic inflammation of the bladder muscles and symptoms like frequent urination and bladder pain.

IC is associated with a deficiency in a compound called glycosaminoglycan. Because your body converts glucosamine into glycosaminoglycan, it’s speculated that taking glucosamine supplements could help manage IC (18).

Unfortunately, reliable scientific data to support this theory is lacking.

Inflammatory bowel disease

Inflammatory bowel disease (IBD) is a condition that causes chronic inflammation of the intestines, often leading to symptoms like bloating, stomach cramps, and diarrhea. Like IC, it’s associated with a deficiency in glycosaminoglycan.

A study in mice with IBD indicated that supplementing with glucosamine could reduce inflammation (19).

In one small study, 34 participants with IBD who took N-Acetyl glucosamine — another form of glucosamine supplements — for 4 weeks reported significant improvements in symptoms like pain and diarrhea (18).

However, the study was not blinded and contained no control group. This prevents any conclusions from being drawn about the efficacy of glucosamine for improving IBD-related symptoms.

Multiple sclerosis

Multiple sclerosis (MS) is a chronic condition that affects your central nervous system. Symptoms vary but can include fatigue, tremors, and trouble walking, talking, and seeing.

Some people claim that glucosamine could be an effective treatment for MS, but supporting research is lacking.

For example, one review showed no significant impact of glucosamine supplements on MS relapse rate or disease progression (20).

Glaucoma

Glaucoma is an eye disease that can cause some vision loss and even blindness. Some people believe it can be treated with glucosamine.

Promisingly, research in rats indicates that glucosamine sulfate might promote eye health by reducing inflammation and providing antioxidant effects in your retina — the back of your eye that’s responsible for receiving light and sending vision info to your brain (21).

However, one study in humans indicated that glucosamine supplements may instead increase glaucoma risk in older adults — a group that’s already at heightened risk of developing glaucoma (22).

Temporomandibular joint disorders

Some sources claim that glucosamine is an effective therapy for temporomandibular joint (TMJ) disorders. These are health issues related to your jaw — like jaw pain and locking of the jaw joint. However, research to support this claim remains insufficient.

One small study showed a significant reduction in pain and inflammatory markers as well as increased jaw mobility in participants who received a combined supplement of glucosamine sulfate and chondroitin (23).

Another study showed a significant improvement in maximum mouth opening and pain reduction — demonstrated by reduced inflammatory markers — after taking 1.5 grams of glucosamine and 1.2 grams of chondroitin sulfate daily for 8 weeks (24).

Although these study results are promising, they don’t offer enough data to support any definitive conclusions. As such, more research is needed on the topic.

Summary

While glucosamine is often regarded as an effective treatment for a wide variety of conditions, there is no conclusive data on its impact. Ultimately, more research is needed.

Though broad claims are made about glucosamine’s positive effects on many conditions, available research only supports its use for a narrow range of them.

Currently, the strongest evidence supports glucosamine sulfate use for the long-term treatment of OA symptoms. But even then, evidence remains inconclusive (25, 26, 27).

Besides this, glucosamine is less likely to be an effective treatment for other diseases or inflammatory conditions.

If you’re still considering using glucosamine, consider the quality of the supplement you choose.

It’s best to check for third-party certification to ensure you’re getting exactly what you’re paying for. Manufacturers willing to have their products tested for purity tend to have higher standards.

ConsumerLab, NSF International, and US Pharmacopeia (USP) are a few independent companies that provide certification services. If you see one of their logos on your supplement, it’s more likely to be of good quality.

Summary

Most research supports the use of glucosamine-sulfate solely for managing OA symptoms, but even then, evidence remains inconclusive. Based on available studies, the supplement is less likely to be effective for any other conditions.

The typical glucosamine dosage is 1,500–3,000 mg per day, which you can take at once or in multiple smaller doses (4, 8, 10).

Glucosamine supplements are made from natural sources like shellfish shells or fungi or manufactured artificially in a lab.

Glucosamine supplements are available in three forms (1):

  • glucosamine sulfate
  • glucosamine hydrochloride
  • N-Acetyl glucosamine

There appear to be no differences between their anti-inflammatory effects. Most studies that have found glucosamine effective for improving osteoarthritis symptoms used the sulfate version (28).

Glucosamine sulfate is commonly sold in combination with chondroitin sulfate.

Summary

Glucosamine is typically dosed at 1,500–3,000 mg per day. Of the available forms, glucosamine sulfate — with or without chondroitin — is likely the most effective.

Glucosamine supplements are likely safe for most people. Still, some risks exist that are worth keeping in mind (29).

Possible adverse reactions include (30):

  • nausea and vomiting
  • diarrhea
  • heartburn
  • abdominal pain

You should not take glucosamine if you’re pregnant or breastfeeding due to a lack of evidence on its safety.

Also, know that glucosamine may have a small hypoglycemic effect in people with type 2 diabetes, though the risk is relatively low. If you have diabetes or are taking diabetes medications, talk with your doctor before taking glucosamine (6).

Glucosamine may also increase glaucoma risk. Therefore, it shouldn’t be taken by those at risk of developing glaucoma, including those with a family history of glaucoma, people ages 60 or older, and those who have diabetes, heart disease, or high blood pressure (31).

Summary

Glucosamine is likely safe for most people, although mild gastrointestinal upset has been reported in some individuals. Avoid these supplements if you are at risk for glaucoma or if you’re pregnant or breastfeeding.

Glucosamine exists naturally within your body and plays a vital role in the development and maintenance of healthy joints.

Glucosamine supplements are commonly taken to treat various joint, bone, and inflammatory diseases like IBD, IC, and TMJ. Still, most research only inconclusively supports its effectiveness for long-term osteoarthritis symptom management.

It appears safe for most people at a dosage of 1,500–3,000 mg per day but may cause mild side effects.