In healthy cells, there are substances to prevent blood clotting. The substances are called phospholipids. Lupus anticoagulants are antibodies that attack phospholipids. Thus, people with lupus anticoagulants may have a very high risk of forming blood clots.
Most often, lupus anticoagulants are found in people with systemic lupus erythematosus. They're also found in people who take medicines such as phenothiazines, phenytoin, hydralazine, quinine, or the antibiotic amoxicillin, or people who have inflammatory bowel disease (Crohn disease and ulcerative colitis), infections, or certain kinds of tumors.