Heparin is a medication used as a blood thinner to prevent blood from clotting inside blood veins, arteries and the lungs, according to Drugs.com. It is also administered to patients before surgery to prevent blood clots. Heparin is administered as an injection under the skin or intravenously.
Drugs.com further mentions that patients should not use Heparin when suffering from uncontrolled bleeding or a very low level of blood platelets. Patients should also notify their doctor if suffering from infections in the heart; uncontrolled hypertension; liver disease; hemophilia; stomach or intestinal disorder; or experiencing a menstrual period. Possible side effects include numbness or weakness, severe headache, confusion, fever, coughing, chest pain or difficulty with breathing.