Hi, Welcome to hCM, You are taking slow release niacin used for Lipid abnormality.This is useful in low level of HDL, usually undesirable flushing occurs although much lower with this type extended release preparation. Bleeding usually is not caused but may be that you have some internal lesion like anal fissure or hemorrhoids. please visit a general surgeon to do a internal examination and proctoscopy to see source of bleeding.You should also get complete blood count and coagulation tests like bleeding time ,clotting time and prothrombin time, which will tell us about bleeding diathesis. Once cause is confirmed then it can be treated accordingly. Please take care. Good Luck. Dr.Akhilesh Dubey M.D.