Around 6 million people in the US take glucosamine supplements and yet their effects remain controversial. While glucosamine is essential for healthy joints and youthful skin, it has some other surprising benefits. But does it work? Read on to uncover the science, reviews, contraindications, and whether the side effects are worth the gains.

What Is Glucosamine?

Glucosamine is a naturally occurring substance in the body. It works to build connective tissue, cartilage, ligaments and other structures in our body. Plus, it lubricates and strengthens the joints, enabling smooth movement [R, R].

Chemically speaking, glucosamine is a relatively simple substance. It’s classified as an amino sugar. Shellfish (lobsters, shrimp, crabs) are rich in chitin, a highly-resistant material made of long chains of glucosamine. Manufacturers use them as raw material for glucosamine supplements [R].

Animal bones and connective tissue are also decent food sources of glucosamine [R].

In the US, glucosamine is among the most popular dietary supplement for adults. Many professional athletes rely on it, especially those with joint issues [R, R, R].

But glucosamine is not just for athletes. The European League Against Rheumatism recommends glucosamine as a treatment for osteoarthritis, the leading chronic joint disease in older people [R].

Snapshot of Glucosamine

PROS

  • Helps with osteoarthritis and other joint diseases
  • Boosts cartilage recovery
  • May relieve gut inflammation
  • May improve cardiovascular health
  • Hydrates the skin and removes dark spots

CONS

  • Beneficial joint effects are weak
  • May cause digestive side effects
  • Requires long-term treatment
  • May raise blood glucose and eye pressure
  • Interacts with blood thinners

How It Works

Glucosamine’s secret lies in its ability to boost the production of other connective-tissue-repairing compounds. This way, it acts as the building block of large elastic molecules that impregnate the skin, joints, and ligaments [R].  

For example, glucosamine builds complex molecules known as glycosaminoglycans, such as hyaluronic acid. They give strength and elasticity to our skin, joints, and ligaments [R, R, R].

Most skincare-savvy people will have heard of hyaluronic acid – it’s extremely popular in serums… and for a good reason. It maintains skin moisture and offers powerful anti-aging benefits to the skin. Since glucosamine boosts hyaluronic acid, it’s also used in cosmetics [R].

That’s not all.

Glucosamine also protects cartilage by maintaining collagen structure. Plus, it acts as an anti-inflammatory and antioxidant in the joints, intestines, and blood vessels. In turn, it promises to protect your body against different chronic diseases [R, R, R, R, R, R, R].

Glucosamine may even kill different types of cancer and prevent cancer from spreading – at least in test tubes [R, R, R, R, R].

Remember, glucosamine is no magic pill. Although scientists and practitioners alike are excited about its wide-ranging potential benefits, only a couple have sufficient evidence to back them up.

We’ll dive into those first.

Health Benefits of Glucosamine

1) Helps with Osteoarthritis

Osteoarthritis is the most common joint disease. Destruction of cartilage in the joints and bone deformation cause pain and restrict movement. It usually attacks large joints such as the knee and hip joints. Doctors are still looking for ways to slow or prevent its progression [R].

Knee Osteoarthritis

The majority of research examined the effects of glucosamine on the symptoms and progression of knee osteoarthritis. Given the diverse and conflicting results, we grouped the studies according to their main outcomes and conclusions.

Positive Results

According to a large review of 31 clinical trials, glucosamine improves the symptoms of osteoarthritis better than placebo [R].

In 2 studies with 1,600+ knee osteoarthritis patients, a combination of glucosamine and chondroitin reduced pain, stiffness, and joint swelling. In the first study, this combination was as effective as an NSAID, celecoxib. The other one, however, lacked a control group [R, R].

Glucosamine alone (1,500 mg daily for 1 month) showed the same results in a study on 178 patients, matching ibuprofen (Motrin) but with fewer side effects [R].

In another 60 patients with knee osteoarthritis, glucosamine boosted the beneficial effects of ibuprofen on overall symptoms and joint function [R].

A supplement with glucosamine, chondroitin, and quercetin improved joint function and relieved pain in 46 patients with knee osteoarthritis [R].

Plus, in another study on 38 patients, higher doses of glucosamine (3 g daily for 3 months) reduced the symptoms of knee osteoarthritis [R].

A cream with glucosamine also managed to relieve knee pain in 63 osteoarthritis patients. Other ingredients such as chondroitin and camphor may have contributed to the effects [R].

Mixed Results

Comprehensive reviews and meta-analyses (50+ clinical trials with 3K+ patients) revealed mixed results. Glucosamine reduced knee pain better than placebo but failed to improve joint stiffness and function [R, R, R].

Some scientific reviews found positive results only for specific formulations of glucosamine and its combinations with other supplements (more details in “Supplements and Dosage”) [R, R, R].

In 2 large clinical trials (1,250+ patients, 24 months), glucosamine didn’t significantly improve the symptoms of knee osteoarthritis; it only showed a mild painkiller effect. Lastly, a combination with chondroitin prevented cartilage thinning in 1 trial [R, R].

Negative Results

Glucosamine didn’t help with knee osteoarthritis symptoms – neither alone nor in combination with chondroitin – in 2 clinical trials on 240+ patients [R, R].

Jaw Osteoarthritis

In 2 clinical trials (105 patients, 3 months), glucosamine relieved pain and improved jaw mobility better than ibuprofen [R, R].

However, 6-week treatment with glucosamine (1,200 mg a day) had no effects in 59 patients with jaw osteoarthritis [R].

Summary

Glucosamine provided mild-to-moderate pain relief in most patients with osteoarthritis, but advanced cases may require more effective treatment.

2) Boosts Joint Recovery

Glucosamine is often the go-to supplement for athletes who are prone to joint injuries. In one trial, it improved knee function in 106 athletes with an acute knee injury (1,500 mg daily for 4 weeks) [R].

In professional athletes, glucosamine supplements (1,500 – 3,000 mg, up to 4 months) blocked collagen degradation and thus aided in cartilage recovery [R, R, R].

Low doses of glucosamine (500 – 1,000 mg) showed the same effects in healthy individuals [R].

However, glucosamine supplementation failed to improve post-surgery recovery in 30 athletes with ruptured knee ligaments. The daily dose in this study (1,000 mg) was lower than usual [R].

Overall, glucosamine may support joint and cartilage recovery when dosed properly.

3) May Help with Rheumatoid Arthritis

Unlike osteoarthritis, rheumatoid arthritis is an autoimmune disease that leads to joint inflammation. It causes joint pain and stiffness but may even spread to the entire body [R].

In 51 patients, 3-month treatment with glucosamine notably improved the symptoms of rheumatoid arthritis [R].

On the other hand, a combination of glucosamine, chondroitin, and quercetin had no effect on 22 patients with rheumatoid arthritis [R].

In mice with rheumatoid arthritis, both glucosamine and N-acetyl-glucosamine suppressed joint inflammation and enhanced joint function [R].

Interestingly, a combination of glucosamine and vitamin E blocked oxidative damage and inflammation in rats with rheumatoid arthritis by [R]:

Multiple cell studies have confirmed the anti-inflammatory and antioxidant potential of glucosamine. As a supplement, glucosamine may offer protection against rheumatoid arthritis and other chronic inflammatory diseases [R, R, R, R].

4) Relieves Gut Inflammation

In a clinical trial on 38 patients, glucosamine (3 g daily for 3 months) decreased gut inflammation and blocked the growth of dangerous diarrhea-causing bacteria (Clostridia) [R].

In rats and mice with IBD, glucosamine could [R, R, R]:

  • Combat gut inflammation by blocking inflammatory substances (NF-kB, COX-2, and nitric oxide, TNF-alpha, and IL-6)
  • Repair the gut tissue
  • Prolong survival time

One review pointed to the gut-healing potential of glucosamine and an intricate connection between digestive and joint disorders [R].

5) May Prevent Cancer

In a large observational trial with 75K+ patients, those who consumed glucosamine and chondroitin supplements had lower rates of lung cancer (51%) and colon cancer (45%). According to the researchers, the reduction of colon cancer rates was not significant [R, R].

Another observational trial (2K patients) showed a 21% lower rate of colon cancer among glucosamine and chondroitin users. However, an even larger one (6K+ patients) found no significant connection [R, R].

Glucosamine inhibited the growth of breast cancer and lung cancer in mice [R, R].

In test tubes, glucosamine could kill the cells of [R, R, R, R, R]:

  • Breast cancer
  • Lung cancer
  • Prostate cancer
  • Cervical cancer
  • Brain cancer

6) May Boost Heart Health

Glucosamine may protect your heart by reducing inflammation and enhancing the repair of damaged tissue. However, evidence to support this benefit is still limited to animal and cell-based studies.

In rats, glucosamine protected the animals’ hearts from injury and bleeding by strengthening the proteins and blocking inflammation [R].

In cell studies, glucosamine balanced calcium levels in the heart cells and shielded them against damage [R, R, R].

It may also block inflammation in blood vessels and thus cut the risk of clogged arteries (atherosclerosis) [R, R].

Benefits of Glucosamine for the Skin

7) Anti-Aging Properties

Since glucosamine builds hyaluronic acid and other components of the skin and connective tissues, it may reduce wrinkles and boost skin complexion when added to cosmetic products. Plus, it blocks the production of the skin pigment melanin and thus removes dark skin spots [R, R].

Researchers analyzed skin samples of 8 women who took glucosamine (250 mg daily for 8 weeks). Glucosamine rejuvenated the skin by enhancing collagen and hyaluronic acid production [R].

Glucosamine’s cousin, N-acetyl glucosamine or NAG, also helps maintain a youthful appearance of skin [R, R, R, R].

Recap: Does Glucosamine Work?

Glucosamine may not be the best solution for osteoarthritis, but it can help. In most clinical trials, it provided mild-to-moderate pain relief. For more advanced cases of osteoarthritis, it may not be up for the task.

Long-term treatment (3+ months) with optimal dosage and supplement form increases your chance of success (see “Glucosamine Supplements and Dosage” below for more details).

Glucosamine protects the cartilage and might be a good choice for the prevention of joint injuries in the elderly or professional athletes.

The evidence for anti-aging skin benefits with glucosamine is solid, too. Well-designed clinical trials should confirm other potential benefits of glucosamine before we draw any conclusions.

Glucosamine Supplements and Dosage

Glucosamine sulfate and glucosamine hydrochloride are the two most common salts, and people mostly take them as pills (1,500 mg) or bulk powders (500 – 1,500 mg per serving). Other available forms include:

  • Liquid glucosamine (750 – 2,000 mg of glucosamine hydrochloride per serving)
  • Glucosamine gels and creams for joints and skin care

Most glucosamine supplements also contain chondroitin and other ingredients such as MSM, hyaluronic acid, and turmeric extract.

Vegan glucosamine, derived from fermented corn, is also available in the form of pills or bulk powder. It’s suitable for people with seafood allergy and those who avoid animal products.

Note: Some pills contain NAG or N-acetyl-glucosamine (500 – 750 mg). Although a close derivative of glucosamine, NAG is a different substance with distinct health benefits and side effects. The dosing guidelines will also vary. Most studies we reviewed in this article did not use NAG.

What is the Best Glucosamine Supplement?

At this point, you’re probably wondering how to choose the best glucosamine supplement so let’s see what the evidence says.

The most common forms of glucosamine in supplements are:

  • Glucosamine sulfate
  • Glucosamine hydrate
  • Liquid glucosamine
  • Combinations with chondroitin and MSM

One trial with 600+ patients found higher efficacy of glucosamine sulfate for knee osteoarthritis compared with hydrochloride, although both forms showed mixed results [R].

Glucosamine sulfate probably owes its advantage to better absorption. Sulfur from this form may also help build and protect the cartilage [R, R].

On the other hand, both the sulfate and hydrate were equally effective in one clinical trial [R].

The strongest evidence comes from a series of comprehensive reviews in which a specific crystalline form of glucosamine sulfate was superior to others [R, R, R].

The fact that one pharmaceutical company owns a patent for this formulation may indicate a potential conflict of interests.

Retailers claim better absorption of liquid glucosamine supplements, but no clinical trials have confirmed this yet. When it comes to other ingredients, chondroitin and MSM may boost the effects of glucosamine on knee pain and joint recovery [R, R, R].

To sum it up, crystalline glucosamine sulfate with chondroitin and MSM would be the best choice, but the evidence remains limited.

Now let’s see which dosage you should aim at.

Dosage

The following doses gave positive results in clinical trials:

  • Osteoarthritis and rheumatoid arthritis: 1,500 mg daily for 3+ months
  • Cartilage regeneration: 1,500 – 3,000 mg (athletes) or 1,000 mg daily for 4 months
  • Knee injury recovery: 1,500 mg daily for 1 month
  • Gut inflammation: 3,000 mg daily for 3 months

Glucosamine for Dogs

Chews, capsules, and powders with glucosamine for dogs are all over the market. They claim to have the same beneficial effects on aging dog joints.

Just like in humans, glucosamine showed some beneficial effects in dogs, but they are mostly limited to mild pain relief. Given that most dogs tolerated the treatment well, glucosamine supplements might be worth a try if your dog has joint issues [R, R, R].

The dosage of glucosamine for dogs in the quoted studies was 2,000 mg daily, but it may vary depending on your buddy’s weight. Some vets recommend 500 mg per 10 lbs of body weight.

Despite all the available products explicitly marketed for dogs, they are fine using the human ones, too.

Glucosamine for Cats

Glucosamine for joint disorders in cats doesn’t seem to have any notable effects, but the studies are sparse. Some vets reported clinical success in using glucosamine and chondroitin for joint issues in cats, though.

Due to the lack of data, it’s best to consult your vet first if you’re considering giving your feline friend glucosamine supplements [R, R].

Glucosamine Side Effects & Precautions

Countless clinical trials tested glucosamine supplements, and they haven’t caused any major side effects. In some patients, they may cause digestive issues such as [R, R, R, R]:

  • Nausea
  • Heartburn
  • Bloating
  • Diarrhea

Diabetes and Weight Gain

Glucosamine has a structure similar to glucose and may interfere with its metabolism. However, clinical studies haven’t found adverse effects in patients with controlled diabetes [R, R, R, R].

It may raise blood glucose levels in patients with untreated diabetes or insulin resistance. It’s a good idea to closely monitor blood glucose while taking glucosamine supplements, especially if you have diabetes or at risk [R, R].

If blood glucose and insulin are in check, glucosamine probably won’t cause weight gain and metabolic side effects.

Eye Pressure and Glaucoma

In a clinical trial on 88 patients with osteoarthritis, glucosamine increased eye pressure, especially in older patients. A small observational study (17 patients) came to the same conclusion [R, R].

Due to this effect, glucosamine may raise the risk of glaucoma in the elderly [R].

Glucosamine Side Effects on the Liver

A few case reports indicated a potential of glucosamine to worsen chronic liver disease, but no clinical or safety trials confirmed this effect. In one case, the liver side effects of glucosamine were probably a consequence of an allergic reaction [R].

Sensitive Groups

Most supplement manufacturers derive glucosamine from shellfish so they may not be safe for people with shellfish/seafood allergy. A safety trial on 6 patients with seafood allergy revealed no side effects of glucosamine, but these results are far from conclusive [R].

There’s a solution for people with seafood allergy, and we’ll get there in a minute.

Pregnant women should avoid glucosamine until we know more about its safety. Same goes for children unless they are under medical supervision [R, R].

Drug Interactions

The only significant drug interaction of glucosamine is with blood thinners such as warfarin (Coumadin). In combination with these drugs, glucosamine may prolong bleeding time and increase the risk of bruising [R].

Glucosamine Contraindications

To sum it up, the following groups may want to avoid glucosamine supplements:

  • People with uncontrolled diabetes
  • People with seafood and shellfish allergy
  • Children and pregnant women
  • People on blood thinners
  • People with increased eye pressure and glaucoma

Make sure to consult your doctor before taking glucosamine, especially if you belong to one of the above groups.

Glucosamine Supplement Reviews

Looks like users did their research since most of them are taking glucosamine sulfate in combination with chondroitin and MSM. Although the majority of products deliver 1,500 mg of glucosamine per serving, the content of other ingredients varies a lot.

Most glucosamine supplement reviews are positive: people managed to ease the pain in their knees, but also in elbows, spine, and hips. Some users reported skin benefits as a plus.

Glucosamine is quite popular among dog owners and they also report positive results. Most of them are giving human glucosamine supplements to their “best friends”.

On the other hand, some users have reported a lack of effects or even worsened symptoms in a few cases. Digestive issues and dizziness are common side effects while some people reported high blood pressure and kidney pain.

Buy Glucosamine

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Take-Away:

Glucosamine gives structure and elasticity to your skin, joints, and connective tissue. As we age, the lack of glucosamine may lead to joint pain and wrinkled skin.

Food sources of glucosamine include shellfish, animal bones, skin, and cartilage. Glucosamine is one of the most popular nutritional supplements, especially among athletes and older people with joint issues.

Despite their popularity, glucosamine supplements showed mixed results in people with osteoarthritis and other joint diseases. They can relieve the pain and improve joint function in mild-to-moderate osteoarthritis.

Glucosamine may also help with rheumatoid arthritis and gut inflammation, but the evidence is limited. Cosmetics with glucosamine can remove dark spots and improve skin complexion.

To increase your chance of success, choose supplements with crystalline glucosamine sulfate in a daily dose of 1,500 mg. Chondroitin and MSM may boost its effects. If you have a seafood allergy or avoid animal products, look for a vegan-friendly glucosamine supplement.

Skip glucosamine if you are pregnant; have untreated diabetes, increased eye pressure, or glaucoma; take warfarin or other blood thinners. Children should take glucosamine only under medical supervision.

Glucosamine may also benefit your dog’s joints in a daily dose of 2,000 mg.

About the Author

Aleksa Ristic, MSc (Pharm)

MS Pharm

Aleksa received his MS in Pharmacy from the University of Belgrade, his master thesis focusing on protein sources in plant-based diets.

 

Aleksa is passionate about herbal pharmacy, nutrition, and functional medicine. He found a way to merge his two biggest passions—writing and health—and use them for noble purposes. His mission is to bridge the gap between science and everyday life, helping readers improve their health and feel better.

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