context: Glucosamine sulfate is a natural sugar found in and around the fluid and tissues that cushion your joints. This tissue is called cartilage. Glucosamine is also found in the hard covering of shellfish. Glucosamine sulfate supplements are often made using shellfish. The substance can also be made in a laboratory. Glucosamine sulfate is a widely used supplement that may help ease pain in people with osteoarthritis. Osteoarthritis happens when cartilage breaks down. This can cause joint pain. Millions of people in the U. S. have osteoarthritis. Scientists have been studying glucosamine sulfate alone, and together with another supplement called chondroitin, for many years. Research results have been conflicting. Some studies show the supplement reduces knee pain in people with moderate-to-severe osteoarthritis. However, it doesn't seem to work as well in people who: Have mild knee pain Have had the condition for a long time Are overweight The supplement seems to reduce pain as much as ibuprofen. But it doesn't work as fast. It can take four to eight weeks for glucosamine sulfate to ease pain. Some studies show that glucosamine sulfate may also work for: Osteoarthritis of the hip or spine Arthritis of the temporomandibular joint ( TMJ) in the jaw A study in men also suggests that glucosamine sulfate may help a person bend and flex the knee better after a sudden knee injury. Glucosamine may also slow the progression of osteoarthritis. but the studies are mixed. Optimal doses of glucosamine sulfate have not been established. Supplement ingredients and quality may vary widely from maker to maker. This makes it hard to establish a standard dose. The dose used in many studies to treat knee osteoarthritis was 500 milligrams, taken three times a day. There are different forms of glucosamine. Check the supplement's ingredients. Some may contain glucosamine sulfate. Other supplements may have glucosamine hydrochloride or another type. Most studies have used glucosamine sulfate. Glucosamine is sometimes found in skin creams used to treat arthritis pain. There is no proof that glucosamine can move through your skin. Scientists think the pain relief may be due to other ingredients in the cream. Studies done in a laboratory dish hint that glucosamine sulfate may help fight HIV, the virus that causes AIDS. Much more comprehensive research is needed before scientists can say whether or not this supplement could be helpful for those with the virus. You cannot get glucosamine sulfate from foods. It is a natural chemical found in the human body. It is also found in the shells of shellfish. Glucosamine appears to be safe, even when taken for a few years. Side effects may include: Constipation Diarrhea Drowsiness Headache Heartburn Nausea Rash Glucosamine may affect blood sugar and insulin levels. However, studies are mixed. Talk to your doctor before taking this supplement if you have diabetes or insulin resistance. Animal studies show that glucosamine may further increase LDL "bad" cholesterol levels if you eat a lot of fatty foods. More research is needed. Glucosamine may interfere with some medicines. Do not use glucosamine if you take warfarin ( Coumadin). Doing so raises your risk of bruising and dangerous bleeding. There are reports that glucosamine may also reduce the effectiveness of certain drugs. So use caution when taking glucosamine if you take: acetaminophen ( Tylenol) Certain chemotherapy drugs, including doxorubicin ( Adriamycin, Rubex), etoposide ( Etopiside), and teniposide ( Vumon) Diabetes drugs, including glimepiride ( Amaryl), glyburide ( Dia Beta), insulin ( Novo Log), pioglitazone ( Actos), and rosiglitazone ( Avandia) Talk to your doctor before using this supplement if you are allergic to shellfish. Always tell your doctor about any supplements you are taking, including natural ones and those bought without a prescription. That way, your doctor can check on any potential side effects or interactions with any medications. Supplements are not regulated by the FDA.