Glucosamine is a natural substance in the body and one of the building blocks of cartilage, which helps to cushion your joints.
However, if you have joint pain from osteoarthritis or other musculoskeletal conditions, you’re probably familiar with the glucosamine sulfate that is widely sold as an over-the-counter joint-support supplement.
Molly McDermott, DO, a Cleveland Clinic sports and exercise medicine physician, discusses glucosamine with her patients who have mild to moderate osteoarthritis. She often says to them, “Is glucosamine going to be life-changing? No. Can it help? Can glucosamine be part of your treatment process? Yes.”
What Is Glucosamine?
An amino sugar, glucosamine is a normal component of the cartilage produced in your body. Glucosamine supplements are usually made from shellfish shells (e.g., lobster, crab, and shrimp) or manufactured synthetically in a lab.
Glucosamine is not found in large amounts in food. In the United States, glucosamine is sold over the counter as a dietary supplement in most places that sell vitamins, whereas it is available by prescription in Europe. In the U.S., it is not regulated like a prescription medication.
What Are the Possible Glucosamine Benefits?
Research examining glucosamine’s effects on joint health and osteoarthritis has produced conflicting findings. For instance, a major National Institutes of Health-sponsored trial found that people with mild-to-moderate osteoarthritis who took supplements combining glucosamine and chondroitin sulfate experienced no more relief than if taking a placebo. However, the participants with more advanced arthritis reported significant pain relief from the combination supplement.
More recently, a 2025 Cochrane systematic review looked at whether glucosamine helps people with osteoarthritis. Researchers reviewed 25 studies involving 4,963 participants. Overall, glucosamine may help reduce pain and improve function, and it was unlikely to cause side effects, the investigators concluded. On a 0-to-100 pain scale, people taking glucosamine improved by about 10 points more than those taking a placebo. However, the highest-quality studies found no difference between taking glucosamine and the fake pills, according to the analysis.
Overall, some studies show improvements in pain and function in people with mild to moderate osteoarthritis, while other investigations have found little or no differences in outcomes between glucosamine and fake pills.
“The literature truly is mixed in regards to glucosamine and osteoarthritis,” Dr. McDermott explains. “But, in cases of rheumatoid arthritis or autoimmune-related joint pain, glucosamine has not shown any substantial benefit.
“When it’s milder osteoarthritis pain, starting to just limit function, I’m having the discussion about glucosamine,” she adds.
Some of Dr. McDermott’s patients report improvement in pain and function and sometimes reduced stiffness when taking glucosamine. Since glucosamine has been shown to be safe, with few side effects and medication interactions, there aren’t huge risks in trying it for most people.
“Because of the safety profile, it’s something to consider—especially in those more mild to moderate cases of osteoarthritis,” Dr. McDermott says.
How Does Glucosamine Work?
Glucosamine supplements are believed to help stimulate cartilage cells to produce new collagen and proteoglycans, which are molecules that support the shock-absorbing effects of cartilage in the knees and other joints. The theory is that glucosamine helps to rebuild cartilage worn down in arthritic joints, ease pain, and improve function. Glucosamine is believed to slow some of the joint cartilage wear and tear associated with osteoarthritis.
It does not work quickly. Unlike anti-inflammatory medicines that can ease pain less than an hour after taking them, glucosamine may take a month or more to have an effect.
“You need to take glucosamine for at least six weeks,” Dr. McDermott says. “If you just start taking it one day, you’re not going to notice a change.”
If you notice no improvement after six weeks, she recommends stopping glucosamine and considering other options. One alternative is the spice turmeric, which can easily be added to foods, has anti-inflammatory properties, and is available in most spice aisles in the supermarket.
What Is the Recommended Dosage?
The recommended glucosamine dosage is 1,500 milligrams (mg) per day. You can take it once per day or divide it into two doses of 750 mg or three doses of 500 mg. The daily recommended dose of chondroitin is 1,200 mg.
What Are the Side Effects and Safety Concerns?
Most people experience no side effects from taking glucosamine, although a few may develop mild gastrointestinal discomfort, diarrhea, or constipation.
“I don’t see a lot of side effects in my patients taking glucosamine/chondroitin,” Dr. McDermott says. “The things most commonly reported in the literature are gastrointestinal—nausea, diarrhea, constipation, or bloating.”
Glucosamine has few known drug interactions, but chondroitin may interact with blood thinners—examples include warfarin (Coumadin), apixaban (Eliquis), and rivaroxaban (Xarelto), among others—and increase your risk of bleeding. Your risk is also higher if you take glucosamine with other medications that increase your odds of bleeding, such as nonsteroidal anti-inflammatory drugs like ibuprofen (Advil, Motrin) and naproxen (Aleve). Talk with your healthcare provider before starting glucosamine/chondroitin supplements, especially if you are taking other medications or have other conditions.
Also, compared with prescription medications, glucosamine and other supplements do not face the same regulatory scrutiny and standardized quality controls from the U.S. Food and Drug Administration. Consequently, there’s no guarantee as to the content, quality, and purity of the supplement you purchase.
Who Should Avoid Glucosamine?
Do not take glucosamine if you are allergic to it. Some people with a severe shellfish allergy may need a shellfish-free glucosamine product, since many glucosamine supplements are made from shellfish shells.
Dr. McDermott also advises caution in people with liver disease because in rare cases glucosamine may affect the liver.
If you have other medical conditions or take prescription medications, check with your healthcare provider before starting glucosamine.
Glucosamine Sulfate vs. Glucosamine/Chondroitin
A glucosamine sulfate supplement contains glucosamine alone. Many supplements also include chondroitin sulfate, which is thought to help with water retention to improve the shock-absorbing quality of collagen in cartilage and block destructive enzymes that break down cartilage. Chondroitin is generally derived from cows.
“Glucosamine and chondroitin are components that are actually in parts of our articular cartilage, the cartilage that lines the bones,” Dr. McDermott says.
“Studies are lacking, but based on what I’ve seen in practice, the theory, and looking at the actual anatomy, I recommend taking glucosamine and chondroitin together and trying it for six weeks,” she adds. If it’s not helping after six weeks, stop using the supplement.
How to Choose a Glucosamine Supplement
Consider these recommendations when selecting a glucosamine supplement:
- Talk with your healthcare provider first, especially if you take other medicines or have medical conditions.
- Look for glucosamine products with labels bearing the symbols of independent organizations that test supplements for their quality, purity, and content, such as Consumer Lab and the U.S. Pharmacopeia.
- Get input from your pharmacist or prescriber when you select a supplement brand.
- Consider a preparation containing both glucosamine and chondroitin. The usual recommended dose is 1,500 mg of glucosamine and 1,200 mg of chondroitin per day.
- Start only one new supplement at a time so you can better tell if it’s helping you.
- If you do not feel better after six weeks of glucosamine use, ask your provider about other options.
