Glucosamine is a dietary supplement that may help relieve the pain of arthritis. Aspirin, available as both a prescription and an over-the-counter drug, serves as a pain reliever and anti-inflammatory for a variety of ailments. Although they differ in their mode of action in your body, they share a common characteristic that may make them unsuitable to take at the same time. Seek the advice of your health care provider before you add any supplements to your diet or take them in combination with any drug.
Glucosamine is a small molecule that serves as a building block of large molecules called glycosaminoglycans. Several types of glycosaminoglycans exist in your body, including hyaluronic acid, chondroitin sulfate and heparin. Glucosamine is an integral part of heparin. Heparin functions as an anticoagulant, or blood-thinning agent, by inhibiting the cascade of molecules necessary for clot formation within your blood vessels. The mast cells of your body produce heparin, and it is also available as an injectable drug for treating blood-clotting disorders. Because glucosamine is chemically similar to heparin, taking glucosamine with an anticoagulant may be unsafe.
Aspirin, or salicylic acid, works to relieve pain, reduce inflammation, lower fever and thin your blood. As a blood thinner, aspirin prevents the platelets in your blood from attaching to each other to form a clot. While clot formation is a normal and often vital response to tissue injury, abnormal clot formation in your blood vessels may lead to stroke or heart attack. Aspirin therapy may reduce your risk of these life-threatening events if you are prone to forming abnormal blood clots. In the context of glucosamine supplementation, aspirin may not be safe to take.
While the blood-thinning property of aspirin may be a benefit under certain health conditions, it also carries the risk of excessive bleeding. For example, under aspirin therapy your blood may lose the ability to clot effectively if you have a bleeding injury. Consuming glucosamine supplements while you have aspirin in your body may exacerbate the anticoagulant effect due to glucosamine's chemical similarity to heparin. Although this effect is unproven, you should use caution when taking glucosamine with any drug that may increase your tendency to bleed.
In addition to the possible bleeding risk you may face by combining glucosamine and aspirin, each individual substance has its own caveat. Glucosamine supplements, isolated from the shells of crustaceans, may cause an adverse reaction if you are allergic to shellfish. Aspirin may damage your stomach lining if you drink alcohol at the same time, and it may also cause digestive upset and heartburn.