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What is Coumadin?

Coumadin (warfarin) belongs to the class of medications called anticoagulants. They are often called blood thinners, and they prevent blood clotting. Coumadin has been in use since the 1950s.

What is Coumadin’s generic name?

The generic name of Coumadin is warfarin. Another common brand name is Jantoven.

What does Coumadin treat?

Coumadin treats blood clots, such as in the leg (deep vein thrombosis) and the lung (pulmonary embolus), and prevents them from reoccurring. Doctors sometimes use Coumadin to treat a specific type of irregular heartbeat called atrial fibrillation, which can cause a stroke. Your doctor will determine if you meet the criteria for daily Coumadin if you have any of these conditions.

How do you take Coumadin?

Coumadin comes in oral tablets, with different colors depending on the doses (1mg to 10mg). You can take it with or without food since it is not known to upset the stomach. Your dosage depends on your medical condition.

If you’re taking Coumadin, you’ll have frequent blood tests called International Normalized Ratio (INR). The results of the INR tests dictate whether your doctor should increase or decrease your dosage. This also determines how long you need to take the medication.

You will usually take Coumadin once a day, and it’s best to take it in the evening. Taking it at the same time every day reduces the chance of forgetting it. This also keeps the medication levels stable in your blood.

Here is general dosing advice for Coumadin:

  • Adults with no increased INR response to Coumadin: Take 2-5mg once daily.

  • Older patients, patients with cardiac failure, and patients with a high risk of bleeding: Take 5mg or less once a day.

  • Adults with a heart valve replacement: Take 2-3mg once a day.

    • Infants and adolescents take 0.2mg/kg once a day with adjustments until they reach the desired INR. Weight-based dosage requirements are age-dependent.

Your doctor’s prescription is best suited for you, so continue following their advice.

Seeing results

The results of taking Coumadin vary depending on your condition.

Prescriptions for Coumadin are usually long-term. The length of time you’ll take the medication depends on your INR test results and your medical conditions. 

If your INR results are at proper levels and frequent INR tests show stable results, the medication is working.

Potential side effects of Coumadin

Coumadin has a long list of side effects. Bleeding is the main side effect of Coumadin, and it requires immediate medical attention.

Other side effects that require immediate medical attention are:

  • Bloody stool

  • Blood in the urine

  • Blurred vision

  • Chest pain

  • Confusion

  • Severe headache

  • Excessive bruising

  • Coughing up blood

  • Hives

  • Unexplained swelling

  • Skin peeling

  • Paralysis

  • Death of skin tissue (necrosis)

Some side effects that do not require immediate medical attention are:

  • Hair loss

  • Pain

  • Abdominal bloating 

  • Itching skin

  • Bleeding or oozing sores in your mouth or on your skin

  • Unusual drowsiness

It’s still advisable to report these side effects to your doctor.

Note that this is not the complete list of side effects Coumadin can cause.

Long-term use of Coumadin

Prescriptions for Coumadin are usually for long periods depending on your circumstances.

Short courses of six weeks to six months are usually for a blood clot in the leg or lungs, at which time your doctor will reassess your need for the medication. If you’re at risk for recurrent blood clots, you may be given a prescription for more than six months and sometimes for a lifetime.

Missed doses

If you ever miss a dose of Coumadin, take it if you remember on the same day. Never make up for a missed dosage by taking two doses in a single day.

Never take a double dose of Coumadin unless instructed by your doctor.

Consult your doctor when you miss a dose. They may be able to help you come up with strategies to remember your medication. Setting an alarm and using a daily pill box are good ideas.


Too much Coumadin can have serious effects. Some symptoms include:

  • Heavy bleeding

  • Coughing up blood

  • Bloody or red stool

  • Unusual bleeding or bruising

  • Heavy menstrual bleeding

  • Pink, dark brown, or red urine

  • Red spots under the skin

If any of these symptoms occur, immediately call an ambulance or have someone take you to your nearest emergency room.

What to discuss with your doctor before you start taking Coumadin

Before starting Coumadin, there are important things to discuss with your doctor, including:

  • If you are allergic to Coumadin, its ingredients, and all other allergies that you have.

  • All medications you are taking, including prescription drugs, nonprescription drugs, and herbal medicines. Coumadin interacts with many other drugs and supplements.

  • All past and present medical conditions, such as high blood pressure, heart disease, kidney disease, and blood cell disorders. Your doctor will decide if Coumadin is suitable.

  • If you are planning or scheduled to have any medical procedures like surgery or dental operations.

  • If you are pregnant, planning to get pregnant, or are breastfeeding. Coumadin can have severe effects on the fetus.

  • Your current diet and alcohol intake: These affect the Coumadin dosage.

Stopping Coumadin

Do not stop taking Coumadin on your own even if you feel well and think you do not need to take it anymore. Always consult your doctor.

Suddenly stopping Coumadin can trigger your previous condition, putting you at significant risk of blood clotting that can lead to heart attack, pulmonary embolism, deep vein thrombosis (DVT), or strokes.

Your doctor may advise taking a lower dose of Coumadin or stopping the medication temporarily for a few days before a medical procedure. Your doctor may prescribe a different type of blood thinner that is shorter acting during this time to avoid bleeding complications during operations. Be sure to discuss this fully with your doctor before the procedure.

Coumadin and pregnancy

Coumadin is not recommended for use during pregnancy. However, pregnant women with a mechanical heart valve at risk of dangerous blood clots should discuss the risks and benefits of Coumadin with their healthcare provider.

Coumadin has serious and even fatal effects on the unborn baby. These include:

  • Spontaneous abortion

  • Congenital disabilities

  • Stillbirth

  • Preterm birth

  • Fetal hemorrhage

Discuss reliable forms of birth control with your doctor while you’re taking Coumadin and an additional one month after stopping the medication.

If you plan to become pregnant or suspect that you are pregnant, inform your doctor right away. They may prescribe another medication to use during pregnancy.

Using Coumadin while breastfeeding is unlikely to cause harm to your child; however, it is always a good idea to consult your doctor before breastfeeding.

Interaction with other drugs

Before taking Coumadin, it is vital to tell your doctor about all other medications and supplements you are currently taking. Coumadin interacts with many medicines and over-the-counter remedies.

Some medications can decrease the effectiveness of Coumadin and increase the risks of clotting. Others can make Coumadin’s effects stronger, make the blood too thin, and promote bleeding.

Some medications that interact with Coumadin are:

  • NSAIDs, including acetaminophen, naproxen sodium, ibuprofen, and aspirin 

  • Antacids

  • Antifungal medications

  • Cold or allergy medicines

  • Antibiotics

This is not the complete list of drugs that interact with Coumadin. Read the product label or ask your doctor or pharmacist for more information.

Allergy information

If you’re allergic to the ingredients of Coumadin, you should not take this medication. Refer to the product label to see the complete list of ingredients. Allergic reactions can occur when taking this medication, although this is uncommon.

Common allergic reaction symptoms include: 

  • Hives/rash

  • Difficulty breathing

  • Swelling of the face, mouth, and throat

  • Swallowing difficulties

Clinical trial history¹

For atrial fibrillation

Warfarin significantly reduces the risk of stroke in patients with non-rheumatic atrial fibrillation (AF).

Trials in patients with atrial fibrillation (AF) suggest a benefit from antithrombotic therapy with Coumadin.

For mechanical heart valves

A study of 254 patients with mechanical prosthetic heart valves demonstrated positive results, reducing the risk of forming potentially fatal blood clots. The thromboembolism-free interval was significantly longer in patients treated with warfarin alone compared with dipyridine/aspirin treatments and pentoxifylline/aspirin treatments.

Tips and advice for taking Coumadin

Coumadin increases the risk of bleeding. Bruises, cuts, and injuries can potentially bleed excessively, so it is advisable to avoid activities that can cause these issues.

Some helpful tips include:

  • Avoid high contact physical sports.

  • Switch to a softer bristled toothbrush and use waxed dental floss to reduce the risk of bleeding gums.

  • Be careful when shaving. An electric razor can reduce the risk of bleeding.

  • The dosage for Coumadin is not the same for everyone. Your doctor will prescribe what’s best for you. Always follow your doctor’s prescription.

  • It’s wise to maintain a consistent diet, and you should tell your doctor about any dietary changes. Any changes in your food, including leafy green vegetables and alcohol intake, can change your body’s reaction to the medication.

  • It is advisable to wear a medical alert necklace or bracelet that says you are taking Coumadin.

  • Ask for advice if you have any questions about Coumadin.

  • Report any side effects you experience while taking Coumadin. Some side effects are harmful and can cause more problems if not treated immediately.

  • If you need to undergo surgery, dental procedures, or any medical procedures, inform all your doctors at least two weeks prior that you are taking Coumadin in case your dosage needs adjusting.

  1. Coumadin (warfarin sodium) tablets label | Food and Drug Administration


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Here at HealthMatch, we’ve done our best to ensure that the information provided in this article is helpful, up to date, and, most importantly, accurate.

However, we can’t replace the one-to-one advice of a qualified medical practitioner or outline all of the possible risks associated with this particular drug and your circumstances.

It is therefore important for you to note that the information contained in this article does not constitute professional medical or healthcare advice, diagnosis or recommendation of treatment and is not intended to, nor should be used to, replace professional medical advice. This article may not always be up to date and is not exhaustive of all of the risks and considerations relevant to this particular drug. In no circumstances should this article be relied upon without independent consideration and confirmation by a qualified medical practitioner.

Your doctor will be able to explain all possible uses, dosages, precautions, interactions with other drugs, and other potential adverse effects, and you should always talk to them about any kind of medication you are taking, thinking about taking or wanting to stop taking.

Curious about clinical trials?

Access the latest treatments and medications. unavailable elsewhere - entirely free of charge. We make it easy to take part.