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How It Works
Normally, when an injury that causes
bleeding occurs, the body sends out signals that cause blood to clot at the
wound, and the clot naturally breaks down as the wound heals. A person prone to
abnormal clotting has an imbalance between clot formation and clot breakdown.
Warfarin prevents new clots from forming and
prevents existing clots from growing by stopping the production of certain
proteins that are needed for blood to clot. Warfarin does not break up or dissolve
existing blood clots. Warfarin is a type of anticoagulant medicine.
Why It Is Used
Warfarin is used to prevent or treat
deep vein thrombosis and
pulmonary embolism. It can also be used for stroke
prevention in some cases.
How Well It Works
Warfarin reduces the chance that a
new blood clot will form or that an existing blood clot will get larger.
Bleeding is the most common side effect
Know the signs of bleeding
Call 911 if:
- You cough up blood.
- You vomit blood or what looks like coffee grounds.
- You pass maroon or very bloody stools.
Call your doctor right away if:
- You have new bruises or blood spots under your skin.
- You have a nosebleed that doesn't stop quickly.
- Your gums bleed when you brush your teeth.
- You have blood in your urine.
- Your stools are black and look like tar or have streaks of blood.
- You have heavy period bleeding or vaginal bleeding when you are not having your period.
If you are injured, apply pressure to stop the bleeding. Realize that it
will take longer than you are used to for the bleeding to stop. If you can't get the bleeding to stop, call your doctor.
Warfarin may also cause a skin rash.
See Drug Reference for a full list of side effects.
(Drug Reference is not available in all systems.)
What To Think About
When you take warfarin, you need to take extra steps to avoid bleeding problems.
- Get regular blood tests.
- Prevent falls and injuries.
- Eat a steady diet, and pay attention to foods that contain vitamin K.
- Tell your doctors about all other medicines and vitamins that you take.
For more information, see:
- Warfarin: Taking your medicine safely.
what to do if you miss a dose of anticoagulant.
Pregnancy. Do not take warfarin if you are pregnant or may become pregnant. If you are
taking warfarin and think you may be pregnant, call your doctor. Warfarin can cause birth defects. If you
become pregnant while taking warfarin, your doctor may recommend that you
switch to another anticoagulant medicine called heparin while you are pregnant.
Complete the new medication information form (PDF)(What is a PDF document?) to help you understand this medication.