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Prevents blood clots.

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Prescription onlyLower-cost generic available

Our bottom line

Coumadin (Warfarin) is an old, cheap, and effective medicine to prevent blood clots, but it requires some monitoring, dose adjustments, and even lifestyle changes.


  • Oral blood-thinning medicine that prevents blood clots from forming or getting bigger.
  • Prevents complications of blood clots that can cause extreme discomfort or death. Examples include stroke (blood clots in the brain), pulmonary embolism (blood clots in the lungs causing trouble breathing), or deep vein thrombosis (blood clots in the legs causing pain and blood vessel damage).
  • Has an antidote, Vitamin K, in case of a major accidental bleeding.
  • Coumadin (Warfarin) has been around for a long time, so we know a lot about how well it works and what the risks are.
  • It's dirt cheap.
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  • Raises your risk of bleeding and bruising.
  • Requires routine blood testing (called an INR) to see how well the medicine is working for you and to make the dose just right for you.
  • Many lifestyle factors can affect how well warfarin works, such as diet, alcohol, and activity level, so it's important that you try to stay consistent with your behaviors.
  • Lots of interactions with other drugs or supplements. Always check with your doctor or pharmacist before starting any new meds.

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What to expect when you take Coumadin (Warfarin) for Anticoagulant

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Tips from our pharmacists
  • Thins your blood to prevent clots from forming or getting bigger. Doesn't break up existing clots.
  • The amount you need depends on your diet, other medical problems, and genes.
  • Take it exactly as instructed.
  • Can raise your risk of bleeding or bruising.
  • Requires regular blood tests to get your dose right.
  • Interacts with a lot of medicines and supplements. Don't start any new meds without talking to your doctor.
  • Eat foods containing consistent amounts of Vitamin K.
  • Tell your doctor immediately if you fell or if you have unusual bleeding, bruising, swelling, or changes in vision and coordination.
  • Get a medical bracelet so that people know you're on a blood thinner during an emergency situation.
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Side effects for Coumadin (Warfarin)

Manufacturers don’t say how common these side effects are

  • Abdominal pain
  • Bloating
  • Blood vessel inflammation
  • Change in taste
  • Chills
  • Diarrhea
  • Elevated liver enzymes
  • Excessive bleeding
  • Gas
  • Hair loss or baldness
  • Hypersensitivity/allergic reactions
  • Itching
  • Liver inflammation
  • Nausea
  • Necrosis of skin and other tissues
  • Rash
  • Rash
  • Systemic atheroemboli
  • Tracheal or tracheobronchial calcification
  • Vomitting

Risks and Warnings for Coumadin (Warfarin)

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    • Higher risk if:
    • Dose too high
    • Age greater than 65
    • History of gastrointestinal bleeding
    • High blood pressure
    • Kidney or liver problems
    • Drug interactions
    • Change in lifestyle or diet
    • Illnesses
    • Alcohol
    • Certain genetic makeup

    Coumadin (Warfarin) is a blood thinner that makes it harder for your blood to clot. Your body may not be able to stop bleeds the way it normally does. Regular monitoring through blood tests, taking the exact amount as instructed, and having a consistent diet can lower your risk of bleeding. Let your doctor know about any persistent or frequent bleeding or bruising, pink urine, red or coffee-ground like stools. If you are bleeding a lot for more than 15 minutes, have a bruise that is getting bigger instead of better, or have fallen and hit your head, go get immediate medical help. In the hospital, doctors can give you a medicine that can reverse the effects of Coumadin (Warfarin).

    This is a black box warning. The FDA requires this warning when there is a significant risk of serious or life-threatening effects that anyone taking the drug should consider.

Means that some groups have a high risk of experiencing this side effect

Tips from pharmacists and people taking Coumadin (Warfarin)

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The FDA category for this medication is X. It is advised that you: Unsafe
  • Upsides and downsides from our pharmacists
  • Many lifestyle factors can affect how well warfarin works, such as diet, alcohol, and activity level, so it's important that you try to stay consistent with your behaviors.
  • Tips from our pharmacists
  • Eat foods containing consistent amounts of Vitamin K.
  • Take at same time daily, get your INR blood test per Dr. & eat same amounts of vitamin k rich foods daily
  • Very hard to adjust dosage based on a diet that includes a wide variety of foods and in particular the healthier green foods that contain high levels of vitamin K