SIDE EFFECTS: Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects. Although very unlikely, this medication can cause bleeding if its effect on your clotting proteins is too much. Tell your doctor right away if you develop any signs of serious bleeding, including unusual pain/swelling/discomfort, prolonged bleeding from cuts or gums, persistent nosebleeds, unusually heavy/prolonged menstrual periods, unusual/easy bruising, dark urine, black stools, severe headache, unusual dizziness. Some patients can have certain bad reactions to heparin (heparin-induced thrombocytopenia-HIT or heparin-induced thrombocytopenia and thrombosis-HITT). This can occur during treatment and up to several weeks after treatment with heparin has stopped. Get medical help right away if you have any very serious side effects, including: pain/loss of feeling in the arms/legs, change in color of the arms/legs, chest pain, trouble breathing, confusion, weakness on one side of the body, slurred speech, vision changes. A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing. This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist. In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch. In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

PRECAUTIONS: Before using heparin, tell your doctor or pharmacist if you are allergic to it; or to pork products; or if you have any other allergies. This product may contain inactive ingredients (such as benzyl alcohol found in some brands), which can cause allergic reactions or other problems. Talk to your pharmacist for more details. Before using this medication, tell your doctor or pharmacist your medical history. Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products). During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor. This medication does not pass into breast milk. Consult your doctor before breast-feeding.

DRUG INTERACTIONS: See also How to Use section. Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval. This medication may interfere with certain laboratory tests (including prothrombin time), possibly causing false test results. Make sure laboratory personnel and all your doctors know you use this drug.

OVERDOSE: If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center. Symptoms of overdose may include: easy/unusual bruising, easy/unusual bleeding such as persistent nosebleeds, blood in urine, black stools.