Table of Contents > Drug > Warfarin Print



Related terms
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    Related terms
    • Brand Names: U.S.: Coumadin®;Jantoven®
    • Brand Names: Canada: Apo-Warfarin®;Coumadin®;Mylan-Warfarin;Novo-Warfarin;Taro-Warfarin

    • It is used to thin the blood so that clots will not form.
    • Warfarin changes the body's clotting system. It thins the blood to stop clots from forming.


    How to take

    • Oral and shot:
    • Use as you have been told, even if you are feeling better.
    • Take this drug at the same time of day.
    • To gain the most benefit, do not miss doses.
    • Keep your use of vitamin K the same from day to day. Talk with your doctor. Do not make changes in your normal diet. Eat only little bits of green, leafy veggies (alfalfa, asparagus, broccoli, brussel sprouts, collard greens, cabbage, cauliflower, kale, lettuce, spinach, water cress), green tea, liver, and some veggie oils. Foods like these may change how this drug works.
    • Follow the diet and workout plan that your doctor told you about.
    • Oral:
    • Take with or without food. Take with food if it causes an upset stomach.
    • Shot:
    • It may be given as a shot into a vein.

    Missed Dose

    • Oral:
    • Take a missed dose as soon as you think about it.
    • If it is close to the time for your next dose, skip the missed dose and go back to your normal time.
    • Do not take 2 doses at the same time or extra doses.
    • Do not change the dose or stop this drug. Talk with the doctor.


    • Tablet:
    • Store at room temperature.
    • Protect from water. Do not store in a bathroom or kitchen.
    • Protect from light.
    • Shot:
    • This drug will be given to you in a hospital or doctor's office. You will not store it at home.



    • This drug may cause very bad bleeding. Follow how to use exactly. Have your blood work checked as you have been told by your doctor, do not miss visits. Closely read the part in this leaflet which lists when to call your doctor.
    • Sometimes drugs are not safe when you take them with certain other drugs. Taking them together can cause bad side effects. This is one of those drugs. Be sure to talk to your doctor about all the drugs you take.
    • Please read the medication guide.


    • If you have an allergy to warfarin or any other part of this drug.
    • Tell your doctor if you are allergic to any drugs. Make sure to tell about the allergy and what signs you had. This includes telling about rash; hives; itching; shortness of breath; wheezing; cough; swelling of face, lips, tongue, or throat; or any other signs.
    • If you have any of these health problems: Anesthesia given in your spine, aneurysm, bleeding problems, diverticulitis, drink too much alcohol, heart valve infection, liver disease, low platelet count, pericarditis, polyarthritis, poor eating habits, recent surgery of the eye or brain, very high blood pressure, unsteadiness, or warfarin-induced necrosis.
    • If you know that you will not take the drug as you have been told.
    • If you are pregnant or may be pregnant.


    • Wear disease medical alert ID (identification).
    • Use care to stop injury and avoid falls or crashes.
    • If you fall a lot, talk with your doctor.
    • If you have bleeding problems, talk with your doctor.
    • You may bleed more easily. Be careful and avoid injury. Use a soft toothbrush and an electric razor.
    • If you have high blood pressure, talk with your doctor.
    • If you have kidney disease, talk with your doctor.
    • If you have liver disease, talk with your doctor.
    • If you have thyroid disease, talk with your doctor.
    • If you have had an ulcer or bleeding from your stomach or bowel, talk with your doctor.
    • If you have a weak heart, talk with your doctor.
    • Have your blood work checked often. Talk with your doctor.
    • Check all drugs you are taking with your doctor. This drug may not mix well with some other drugs.
    • Keep a list of all your drugs (prescription, natural products, vitamins, OTC) with you. Give this list to your doctor.
    • Do not donate blood while using this drug and for 5 days after stopping.
    • Tell dentists, surgeons, and other doctors that you use this drug.
    • Take good care of your teeth. See a dentist often.
    • Talk with your doctor before using products that have aspirin, blood thinners, garlic, ginseng, ginkgo, ibuprofen or like products, pain drugs, or vitamin E.
    • Talk with your doctor before taking multivitamins, natural products, and diet aids. These may have vitamin K in them.
    • Avoid beer, wine, or mixed drinks.
    • If you stop smoking, talk with your doctor. How much drug you take may need to be changed.
    • Use birth control that you can trust to stop pregnancy while taking this drug.
    • Tell your doctor if you are breast-feeding.

    Side Effects

    • Bleeding problems.
    • Headache.
    • Upset stomach or throwing up. Many small meals, good mouth care, sucking hard, sugar-free candy, or chewing sugar-free gum may help.

    Contact a healthcare provider

    • If you think there was an overdose, call your local poison control center or ER right away.
    • Signs of a very bad reaction to the drug. These include wheezing; chest tightness; fever; itching; bad cough; blue or gray skin color; seizures; or swelling of face, lips, tongue, or throat.
    • Very bad dizziness or passing out.
    • A fall or crash when you hit your head. Talk with your doctor even if you feel fine.
    • Swelling, warmth, or pain in the leg or arm.
    • Change in thinking clearly and with logic.
    • Very bad headache.
    • Very upset stomach or throwing up.
    • Very bad back pain.
    • Very bad belly pain.
    • Black, tarry, or bloody stools.
    • Blood in the urine.
    • Coughing up blood.
    • Throwing up blood.
    • Any bruising or bleeding.
    • Very heavy periods (menstrual bleeding).
    • Change in skin color to black or purple.
    • Feeling very tired or weak.
    • Very loose stools (diarrhea).
    • An infection.
    • Any rash.
    • Side effect or health problem is not better or you are feeling worse.

    General Statements

    • If you have a very bad allergy, wear an allergy ID at all times.
    • Do not share your drugs with others and do not take anyone else's drugs.
    • Keep all drugs out of the reach of children and pets.
    • Most drugs may be thrown away in household trash after mixing with coffee grounds or kitty litter and sealing in a plastic bag.
    • In Canada, take any unused drugs to the pharmacy. Also, visit to learn about the right way to get rid of unused drugs.
    • Keep a list of all your drugs (prescription, natural products, vitamins, OTC) with you. Give this list to your doctor.
    • Call your doctor for help with any side effects. If in the U.S., you may also call the FDA at 1-800-FDA-1088 or if in Canada, you may also call Health Canada's Vigilance Program at 1-866-234-2345.
    • Talk with the doctor before starting any new drug, including OTC, natural products, or vitamins.

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    The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.