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Drugs, Devices & Supplements

Understanding Coumadin

(Also Called 'Warfarin')

Your doctor has put you on an anticoagulant medication. "Anti" means against and "coagulant" means causing blood to clot. Therefore, an anticoagulant medication controls the way your blood clots inside your blood vessels.

This handout contains information about the anticoagulant medication warfarin (Coumadin®). Your understanding of this information will help make your anticoagulant therapy as successful as possible, reduce the chance of complications. Be sure to talk with your doctor if you have any questions.

What anticoagulants do?

An anticoagulant helps your body control how fast your blood clots; therefore, it prevents clots from forming inside your arteries, veins or heart during certain medical conditions.

If you have a blood clot, an anticoagulant may prevent the clot from getting larger. It also may prevent a piece of the clot from breaking off and traveling to your lungs, brain or heart. The anticoagulant medication does not dissolve the blood clot. With time, however, this clot may dissolve on its own.

Blood tests you will need

The blood tests for clotting time are called prothrombin time (Protime, PT) and international normalized ratio (INR). These tests help determine if your medication is working. The tests are performed at a laboratory, usually once a week to once a month, as directed by your doctor. Your doctor will help you decide which laboratory you will go to for these tests.

The test results help the doctor decide the dose of warfarin (Coumadin) that you should take to keep a balance between clotting and bleeding.

Important things to keep in mind regarding blood tests include:

  • Have your INR checked when scheduled.
  • Go to the same laboratory each time. (There can be a difference in results between laboratories).
  • If you are planning a trip, talk with your doctor about using another laboratory while traveling.

The dose of medication usually ranges from 1 mg to 10 mg once daily. The doctor will prescribe one strength and change the dose as needed (your dose may be adjusted with each INR).

The tablet is scored and breaks in half easily. For example: if your doctor prescribes a 5 mg tablet and then changes the dose to 2.5 mg (2½ mg), which is half the strength, you should break one of the 5 mg tablets in half and take the half-tablet. If you have any questions about your dose, talk with your doctor or pharmacist.

What warfarin (Coumadin) tablets look like

Warfarin is made by several different drug manufacturers and is available in many different shapes. Each color represents a different strength, measured in milligrams (mg). Each tablet has the strength imprinted on one side, and is scored so you can break it in half easily to adjust your dose as your doctor instructed.

How to take warfarin (Coumadin)

  • Take the dose as instructed once a day.
  • Take the dose at the same time each day. We recommend 5 p.m.
  • The medication can be taken before or after food.
  • If you forget to take your dose and remember within 8 hours, take the dose. If it is past 8 hours, wait until the next day and take only the prescribed dose for that day. DO NOT TAKE A DOUBLE DOSE.
  • If you forget two or more days in a row, call your doctor. The dose may need to be changed.
  • When you take the dose, check off the day on your home calendar.
  • Refill your prescription 1 week before the end of your supply to avoid missing a dose.
  • Continue to take warfarin (Coumadin) as long as your doctor prescribes it.

Where to store Warfarin (Coumadin)

  • Store the medicine at room temperature, away from extreme cold, heat, light or dampness.

Note: Bathroom cabinets usually are not suitable for storing medications because of the dampness.

  • Always keep medications out of the reach of children.

Precautions when taking warfarin (Coumadin)

It is important that you follow these precautions when taking this anticoagulant medication.

Other medications and vitamin supplements

Many medications and vitamins can have an effect on the action of warfarin (Coumadin). These may include:

  • Prescription medications
  • Non-prescription medications such as acetaminophen, aspirin, ibuprofen, non-steroidal anti-inflammatory drugs (NSAIDs), cold and cough medicines, antacids, laxatives, or other medications for pain or discomfort
  • Vitamin preparations containing Vitamin K (phytonadione) or large amounts of vitamins E or C.

Remember to talk with the doctor or pharmacist before you take any medications or vitamins, whether from the drugstore or from another doctor or dentist. This is very important because you may need some of these medications for another medical condition, and your doctor will regulate them with warfarin (Coumadin). Remember, do not stop or start any medications without first talking to your doctor.


Check with your doctor before starting any exercise or sports program.


Be sure to talk with your doctor if you are planning any major diet changes, such as a weight-reducing diet, of if you plan to add any nutritional supplements.

Vitamin K is needed for normal blood clotting. When you are taking an oral anti-coagulant medication such as warfarin (Coumadin), high amounts of Vitamin K can work against the medication. The following guidelines will help control the amount of Vitamin K you are getting from the foods you eat. To help the medicine perform well, you should follow these guidelines:

  • Avoid grapefruit and cranberry products.
  • If you eat spinach, turnip greens, other leafy greens, broccoli, Brussels sprouts, kale, parsley (except as a garnish or minor ingredient), natto (a Japanese dish), liver, or green tea, be sure to eat a consistent amount week to week.
  • Eat all other foods as you normally would.
  • Tell your doctor if you are thinking about changing your current eating habits. Tell your doctor if you are planning to:
    • Eat more or less vegetables.
    • Change to a vegetarian style of eating.
    • Follow a special meal plan to lose or gain weight.
  • Changing your eating habits may mean that you will be getting more or less Vitamin K in the foods you eat. If you change your eating habits, your doctor may want to check your blood more frequently to see how the Coumadin therapy is working.
  • Do not take any herbal supplements that may keep your blood from clotting. The following supplements should not be used when taking anticoagulant medications prior to surgery:
    • Garlic
    • Ginger
    • Gingko biloba
    • Ginseng
    • Feverfew
    • Fish oil
    • Turmeric
    • St. Johns Wort
    • Chondrotin sulfate

Also, tell your doctor if you are currently taking any herbal supplements.

  • Do not take any vitamin supplements that provide more than 100 percent of the Recommended Daily Allowance (RDA). Tell your doctor if you are currently taking more than the RDA of any vitamins (especially vitamins A, C or E).
  • Avoid chronic, heavy drinking of beverages containing alcohol. (Heavy drinking is more than two ounces of liquor, 10 ounces of wine, or 24 ounces of beer per day.)
  • If you drink tea, black tea is recommended because it is not high in Vitamin K. An example of black tea is orange pekoe tea.
  • If you want more servings of vegetables in your daily meal plan, choose vegetables that are not high in Vitamin K, such as corn, squash, potatoes, onions, carrots, cucumbers, celery, peppers, pumpkin and tomatoes.
Daily activities
  • Be careful when using razors. We suggest an electric razor or hair-removing creams to minimize the chance of cuts.
  • Use a soft toothbrush. Brush and floss gently to prevent bleeding from the gums.
Illness and emergencies
  • Keep your doctor's phone number close by in the event of an emergency.
  • Call your doctor if you have any symptoms of illness, such as vomiting, diarrhea, infection or fever. Illness can change the way warfarin (Coumadin) works.
  • Always carry or wear identification that states you are taking warfarin (Coumadin). In an emergency, you may not be able to speak for yourself.
  • Avoid situations where you may get hurt at home or at work. Even minor injuries must be watched for bleeding because warfarin (Coumadin) affects clotting.
  • Falls that cause bruising (bleeding under the skin) and cuts from sharp objects are more serious when you are taking warfarin (Coumadin).
  • Call your doctor if you have any injuries that involve falls or blows to the body or head.

If you do cut yourself and the cut is small, apply constant pressure over the cut until the bleeding stops. This may take up to 20 minutes. If the bleeding doesn't stop, continue to apply pressure and go to the nearest emergency room. If the cut is large, apply constant pressure and get help immediately either by phone or by going to the nearest emergency room.

Pregnancy, surgery and dental work
  • It is important to avoid pregnancy while taking warfarin. Use at least two methods of birth control while taking warfarin.
  • If you are a woman who is taking warfarin (Coumadin) and you are planning to become pregnant, talk with your doctor about the possible risks and ways to reduce those risks. Tell your doctor right away if you become pregnant.
  • Tell all your doctors and dentists before treatment that you are taking warfarin (Coumadin).

You may need to have a blood test and may have to stop taking this anticoagulant for a few days before having a surgical or dental procedure. Check with your doctor before any procedures.

  • Check with your doctor before you travel. You may need to have a blood test and the dose adjusted before you leave.
  • While you travel, carry your medications with you at all times: do not put medications in checked baggage and do not leave them in the car.
Side effects: changes to watch for
  • Bleeding is the most common side effect of warfarin (Coumadin) and can appear as any of several different symptoms.
  • Call your doctor if you notice any of the following signs of bleeding:
    • Bleeding from cuts that won't stop after applying pressure for 20 minutes.
    • Bleeding from the nose, gums or ears.
    • Bruises that appear without reason or become swollen or larger after time.
    • Purplish spots on your skin.
    • Vomiting blood (which may look like coffee grounds).
    • Coughing up blood.
    • Stomach or abdominal pain.
    • Bowel movements that look bright red or black and tarry.
    • Unusual hemorrhoidal bleeding.
    • Reddish or rusty colored urine.
    • Menstrual bleeding that is heavier or longer than normal.
    • Unusual pain or swelling, especially in the joints.
    • Feeling tired or looking pale (symptoms of anemia).
    • Unusual headache.
    • Sudden changes in speech or vision
    • Numbness/tingling in one side of face or arm

If you have any of these symptoms, your doctor may want to do a blood test, change your dose, stop the medication or give you medicine to stop the bleeding.

Warfarin (Coumadin) is safe and effective when used properly. We hope this document has provided you with a better understanding of how to take this medication.

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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: 2/15/2010…#10001