Generic Name: warfarin, Oral tablet

Coumadin,Jantoven

All Brands

  • Coumadin
  • Jantoven
SECTION 1 of 5

Highlights for warfarin

Oral tablet
1

Warfarin is used to treat and prevent blood clots that might result in heart attack, stroke, or death. It’s also used for blood clots in atrial fibrillation, heart valve replacement, venous thrombosis, and pulmonary embolism.

2

Side effects are often related to abnormal bleeding. These include bruising easily, nosebleeds, bleeding from your gums, bleeding from cuts that takes a long time to stop, and heavier than normal menstrual bleeding.

3

Many drugs interact with warfarin. These interactions can be dangerous. Don’t start or stop any other medications, over-the-counter drugs, or supplements without talking to your doctor.

4

Warfarin can lead to miscarriage or birth defects. Use reliable birth control if you’re a female taking warfarin. Tell your doctor immediately if you become pregnant.

5

Warfarin can increase your risk of bleeding, which can be fatal. Avoid any activity or sport that can cause a traumatic injury.

IMPORTANT INFORMATION

FDA Warning

This drug has a Black Box Warning. This is the most serious warning from the Food and Drug Administration (FDA). A black box warning alerts doctors and patients to potentially dangerous effects.

Bleeding risk. Warfarin thins your blood and limits your blood’s ability to clot. It can cause serious bleeding, which can lead to death. You must have regular blood tests and visits with your doctor to monitor your condition. Don’t start or stop any other drug or herbal product unless your doctor tells you to. Tell your doctor if you have any signs or symptoms of bleeding.

Bleeding problems

Tell your doctor if you have an increased risk of bleeding problems, such as being at least 65 years of age, having a history of heart attack or stroke, gastrointestinal bleeding, anemia, diabetes, or kidney problems. Your doctor will decide if warfarin is right for you.

Pregnancy warning

Don’t take this medication if you’re pregnant unless you have a mechanical heart valve. Warfarin may cause birth defects, miscarriage, or death of a fetus.

Drug Features

Warfarin is a prescription drug. It’s available as an oral tablet. 

It’s also available in a generic version. Generic drugs usually cost less. In some cases they may not be available in every strength or form as the brand. Talk to your healthcare provider to see if the generic will work for you. 

This drug may be used as part of a combination therapy. That means you may need to take it with other drugs.

Why It's Used

Warfarin is used to treat blood clots and to lower the chance of blood clots forming in your body. Blood clots can cause a stroke, heart attack, or other serious conditions if they form in your legs or lungs.

More Details

How It Works

Warfarin works by stopping your body from forming blood clots. Warfarin blocks a protein from producing vitamin K—a key vitamin needed for clots to form.

Why It's Used

Warfarin is used to treat blood clots and to lower the chance of blood clots forming in your body. Blood clots can cause a stroke, heart attack, or other serious conditions if they form in your legs or lungs.

Warfarin is approved for:

  • the reduction of risk of heart attack, stroke, or death
  • prevention and treatment of clots with atrial fibrillation or heart valve replacement
  • prevention and treatment of clots in the lower body and in the lungs
SECTION 2 of 5

warfarin Side Effects

Oral tablet

Most Common Side Effects

The most common side effects that occur with warfarin are related to abnormal bleeding.  Possible side effects include:

  • unusual bruising, such as:

    • unexplainable bruises
    • bruises that grow in size
  • nosebleeds

  • bleeding gums

  • bleeding from cuts that takes a long time to stop

  • heavier than normal menstrual or vaginal bleeding

  • pink or brown urine

  • red or black stools

  • coughing up blood

  • vomiting blood or materials that looks like coffee grounds

Serious Side Effects

If you experience any of these serious side effects, call your doctor right away. If your symptoms are potentially life threatening, or if you think you’re experiencing a medical emergency, call 9-1-1.

  • death of skin tissue. This may happen when blood clots form and block blood flow to an area of your body. Symptoms may include:

    • pain
    • color or temperature change to any area of your body
  • purple toes syndrome. Symptoms may include:

    • pain and purple or dark color in your toes

Pharmacist's Advice
Healthline Pharmacist Editorial Team

Warfarin doesn’t cause drowsiness.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this information includes all possible side effects. This information is not a substitute for medical advice. Always discuss possible side effects with a healthcare provider who knows your medical history.
SECTION 3 of 5

warfarin May Interact with Other Medications

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Warfarin can interact with other medications, herbs, or vitamins you might be taking. That’s why your doctor should manage all of your medications carefully. If you’re curious about how this drug might interact with something else you’re taking, talk to your doctor or pharmacist.

Note: You can reduce your chances of drug interactions by having all of your prescriptions filled at the same pharmacy. That way, a pharmacist can check for possible drug interactions.

Food Interactions

Some foods and beverages can interact with warfarin and affect your treatment and dose.

Eat a normal, balanced diet. Talk to your healthcare provider before you make any diet changes. Don’t eat large amounts of leafy, green vegetables. Leafy, green vegetables contain vitamin K. Certain vegetable oils also contain large amounts of vitamin K. Too much vitamin K can reduce the effect of warfarin.

Medications That Might Interact with This Drug

Anticoagulants

Your risk of bleeding is increased when you take warfarin with anticoagulants.

Examples are:

  • Factor XA Inhibitors
    • apixaban
    • edoxaban
    • rivaroxaban
  • Direct thrombin Inhibitors
    • dabigatran

Antiplatelet drugs

Your risk of bleeding is increased when you take warfarin with antiplatelet drugs.

Examples are:

  • P2Y12 platelet inhibitors
    • clopidogrel
    • prasugrel
    • ticagrelor

Nonsteroidal anti-inflammatory drugs (NSAIDs)

Your risk of bleeding is increased when you take warfarin with NSAIDs.

Examples are:

  • diclofenac
  • ibuprofen
  • indomethacin
  • ketoprofen
  • ketorolac
  • meloxicam
  • nabumetone
  • naproxen
  • oxaprozin
  • piroxicam

Antidepressants

Your risk of bleeding is increased when you take warfarin with selective serotonin reuptake inhibitors (SSRIs) and serotonin and norepinephrine reuptake inhibitors (SNRIs).

Examples are:

  • SSRIs:
    • citalopram
    • dapoxetine
    • escitalopram
    • fluoxetine
    • fluvoxamine
    • paroxetine
    • sertraline
    • vilazodone
    • vortioxetine
  • SNRIs:
    • duloxetine
    • venlafaxine

Antibiotics and antifungals

Some antibiotics and antifungals can change how warfarin works in your body. Your doctor may monitor you more closely when you start or stop an antibiotic or antifungal medication.

Examples are:

  • Antibiotics
    • Macrolides:
      • azithromycin
      • clarithromycin
      • erythromycin
      • telitrhomycin
    • Sulfamethoxazole/Trimethoprim
  • Antifungals
    • Azole antifungals
      • fluconazole
      • itraconazole
      • ketoconazole
      • posaconazole
      • voriconazole

Herbal products

Some herbal products may increase the blood thinning effect of warfarin.

Examples are:

  • garlic
  • ginkgo biloba

Some herbal products may decrease the effects of warfarin and increase your risk of blood clots.

Examples are:

  • coenzyme Q10
  • St. John’s wort
  • ginseng

Drugs that affect CYP450 enzyme

CYP450 enzyme helps your body to break down and process medications. Drugs that affect this enzyme may affect how your body handles warfarin.

Drugs that inhibit CYP450

These medications and herbs can increase the amount of warfarin in your body. This can put you at a higher risk of bleeding.

Examples are:

  • amiodarone
  • efavirenz
  • isoniazid
  • metronidazole
  • paroxetine
  • sulfamethoxazole
  • voriconazole

Drugs that induce CYP450

These medications and herbs can make CYP450 work faster. This can lower the amount of warfarin and put you at a higher risk of blood clots.

Examples are:

  • carbamazepine
  • nevirapine
  • phenobarbital
  • rifampin
  • St. John’s wort

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs interact differently in each person, we cannot guarantee that this information includes all possible interactions. This information is not a substitute for medical advice. Always speak with your healthcare provider about possible interactions with all prescription drugs, vitamins, herbs and supplements, and over-the-counter drugs that you are taking.

People with high blood pressure

You may have a higher risk of bleeding if you take warfarin, because your high blood pressure would help to force out blood from some sort of trauma or cut.

People with history of gastrointestinal bleeding

If you have a history of stomach or intestinal bleeding, warfarin may increase your risk of bleeding.

People with heart disease or stroke

If you have heart disease or a history of stroke, your blood vessels may already be damaged and can easily bleed. Warfarin may increase your risk of bleeding.

People with low blood count or cancer

Some cancers can cause internal bleeding. You may have a higher risk of bleeding if you take warfarin.

People who have had head trauma

Warfarin thins your blood. This makes it harder for your blood to clot when you’re bleeding. You may have a higher risk of bleeding if you take warfarin.

People with kidney problems

When you have kidney problems, you can’t get rid of the warfarin from your body as well as if your kidneys were healthy. When warfarin stays in your body longer, it can continue to thin your blood and increase your risk of bleeding.

Pregnant women

Warfarin is a category X pregnancy drug. Category X drugs should never be used during pregnancy.

Warfarin is a category D pregnancy drug if you have a mechanical heart valve. Warfarin may cause harm to the fetus when given to a pregnant woman. However, patients with heart valve disease are already at a higher risk for getting a clot. This can harm both the mother and the baby.

Tell your doctor if you’re pregnant or plan to become pregnant. Warfarin should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Women who are nursing

Warfarin may pass through breast milk. You and your doctor may decide if you’ll take warfarin or breastfeed.

For Seniors

If you are over 60 years of age, you may be more sensitive to warfarin. Your doctor may give you a lower warfarin dose.

For Children

The effectiveness and safety of warfarin haven’t been established in people younger than 18 years old.

Allergies

Warfarin can cause a severe allergic reaction. Symptoms may include:

  • trouble breathing
  • swelling of your throat or tongue
  • hives

Don’t take this drug again if you’ve ever had an allergic reaction to it. Taking it again could be fatal.

SECTION 4 of 5

How to Take warfarin (Dosage)

Oral tablet

All possible dosages and forms may not be included here. Your dose, form, and how often you take it will depend on:

  • your age
  • the condition being treated
  • how severe your condition is
  • other medical conditions you have
  • how you react to the first dose

What Are You Taking This Medication For?

Reduction in the risk of death, another heart attack, or stroke
Form: Oral tablet
Strengths: 1 mg, 2 mg, 2.5 mg, 3 mg, 4 mg, 5 mg, 6 mg, 7.5 mg, and 10 mg
Adult Dosage (ages 18 and older)

Your dose of warfarin sodium is based on your prothrombin time (PT)/international normalized ration (INR) blood test. The typical starting dose is 5 mg to 10 mg once per day. Your dose may change over time based on your test and your condition.

Child Dosage (ages 0-17 years)

A safe and effective dosage hasn’t been established for this age group.

Special Considerations

Seniors: If you’re over 60 years of age, you may be more sensitive to warfarin. Your doctor may give you a lower warfarin dose.

Asian patients: People of Asian descent usually respond to a lower dose of warfarin. Your doctor may give you a lower dose.

Prevention and treatment of clots with atrial fibrillation or heart valve replacement
Form: Oral tablet
Strengths: 1 mg, 2 mg, 2.5 mg, 3 mg, 4 mg, 5 mg, 6 mg, 7.5 mg, and 10 mg
Adult Dosage (ages 18 and older)

Your dose of warfarin sodium is based on your prothrombin time (PT)/international normalized ration (INR) blood test. The typical starting dose is 5 mg to 10 mg once per day. Your dose may change over time based on your test and your condition.

Child Dosage (ages 0-17 years)

A safe and effective dosage hasn’t been established for this age group.

Special Considerations

Seniors: If you’re over 60 years of age, you may be more sensitive to warfarin. Your doctor may give you a lower warfarin dose.

Asian patients: People of Asian descent usually respond to a lower dose of warfarin. Your doctor may give you a lower dose.

Prevention and treatment of clots in the lower body and in the lungs
Form: Oral tablet
Strengths: 1 mg, 2 mg, 2.5 mg, 3 mg, 4 mg, 5 mg, 6 mg, 7.5 mg, and 10 mg
Adult Dosage (ages 18 and older)

Your dose of warfarin sodium is based on your prothrombin time (PT)/international normalized ration (INR) blood test. The typical starting dose is 5 mg to 10 mg once per day. Your dose may change over time based on your test and your condition.

Child Dosage (ages 0-17 years)

A safe and effective dosage hasn’t been established for this age group.

Special Considerations

Seniors: If you’re over 60 years of age, you may be more sensitive to warfarin. Your doctor may give you a lower warfarin dose.

Asian patients: People of Asian descent usually respond to a lower dose of warfarin. Your doctor may give you a lower dose.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this list includes all possible dosages. This information is not a substitute for medical advice. Always to speak with your doctor or pharmacist about dosages that are right for you.
Pharmacist's Advice
Healthline Pharmacist Editorial Team

Warfarin comes with risks if you don’t take it as prescribed.

If You Skip or Miss Doses

Stopping or missing doses can cause complications, such as heart attack, stroke, or blood clots in your veins or lungs. Taking your medication as directed by your doctor, even when you’re feeling well, will give you the best chance of not having the complications.

If You Take Too Much

Taking too much warfarin can lead to life-threatening bleeding. If you take too much, call your doctor or go to the nearest hospital emergency room right away.

What to Do If You Miss a Dose

If you miss a dose, take it as soon as you can. Skip the missed dose if it’s almost time for your next scheduled dose.

Don’t use extra medicine to make up the missed dose. This could result in toxic side effects.

How to Tell If the Drug Is Working

You may not feel any different if warfarin is working. However, you may notice reduced bleeding. Your doctor will do blood tests to see how well the drug is working.

Warfarin may be a short-term or long-term drug treatment.

How long you take this medication depends on the nature of your condition. Your doctor will tell you when and how to stop taking this medication.

You can cut or crush the tablet

Warfarin tablets may be split during therapy. Talk to your healthcare provider to find available pill cutters/splitters.

Store in temperatures from 68–77°F (20–25°C)

Don’t freeze warfarin. Keep it away from light and high temperature.

Note: Keep your drugs away from areas where they could get wet, such as bathrooms. Store drugs away from moisture and damp locations.

Travel

When traveling with your medication:

  • Always carry it with you or in your carry-on bag.
  • Don’t worry about airport X-ray machines. They can’t hurt this medication.
  • You may need to show your pharmacy’s preprinted label to identify the medication. Keep the original prescription-labeled box with you when traveling.

Clinical Monitoring

You must have regular blood tests and visits with your doctor to monitor your condition.  Make sure you don’t miss your appointments because your doctor determines your warfarin dose based on your blood tests.

Your Diet

Some foods and beverages can interact with warfarin and affect your treatment and dose.

Eat a normal, balanced diet. Talk to your healthcare provider before you make any diet changes. Don’t eat large amounts of leafy, green vegetables. Leafy, green vegetables contain vitamin K. Certain vegetable oils also contain large amounts of vitamin K. Too much vitamin K can lower the effect of warfarin.

Are There Any Alternatives?

There are other drugs available to treat your condition. Some may be more suitable for you than others. Talk to your doctor about possible alternatives.

What does the pill look like?

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How Much Does warfarin Cost?

Oral tablet
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Lowest price for warfarin

Kroger Pharmacy $4.00
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Content developed in collaboration with University of Illinois-Chicago, Drug Information Group

Medically reviewed by Creighton University, Center for Drug Information and Evidence-Based Practice on June 25, 2015

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Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up-to-date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or other healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.

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