Coumadin Education

Warfarin (Coumadin) is a blood thinner. It helps prevent clots from forming in blood vessels and in the heart. It is very important to take warfarin exactly as directed by your physician. Too much warfarin can cause bleeding, and not enough warfarin can allow dangerous blood clots to form.

  • Warfarin should be taken at about the same time every day, preferably in the evening.
  • Never skip a pill and never double up on pills if you have missed a dose. Notify your physician if you have missed any pills.
  • Notify all your physicians, your dentist, and pharmacists that you are taking warfarin. You may want to wear a Medic Alert bracelet.
  • Never take any medication, including over the counter (nonprescription) medications without informing your doctor.
  • You will need to have your blood tested regularly, because the correct dose of warfarin for you can change over time. The most common blood test is known as the PT/INR. Your physician will inform you when these tests need to be done.
    • The blood test should be completed as ordered by your doctor. Call your doctor's office for the results within 24-48 hours.
  • Pregnancy requires special restrictions and management of warfarin. Warfarin must not be used between the 6th and 12th weeks of pregnancy. Notify your physician immediately if you become pregnant while on warfarin.


Diet and medications can alter the effect of warfarin on the blood. Foods which are high in Vitamin K decrease the effectiveness of warfarin. While eating small amounts of foods that are rich in vitamin K shouldn't cause a problem, avoid eating or drinking large amounts of the following foods:

  • cauliflower
  • scallions (green onions)
  • peas
  • garbanzo beans (chick peas)
  • asparagus
  • green/herbal teas, coffee
  • liverwurst, beef liver
  • soybean and canola oil
  • spinach
  • kale
  • turnip greens, collard greens, mustard greens
  • broccoli
  • cabbage
  • lettuce, parsley, watercress and endive
  • brussel sprouts

You may eat these foods, but try to eat about the same amount of them each week. Limit your alcohol intake to one or two drinks only per day. Cranberry juice also lowers the effectiveness of Warfarin.

Talk to your doctor before making any major changes in your diet and before starting any over-the-counter medications, vitamins or herbal supplements. If you are unable to eat for several days or have ongoing stomach upset, diarrhea or fever, consult your doctor. These signs and symptoms may mean you need a different dose of warfarin.


Some medications can interact and/or interfere with warfarin causing serious side effects.
You should avoid:

  • Aspirin or any aspirin-containing products (acetylsalicylic acid). Many cold remedies contain aspirin.
  • Vitamin K, Vitamin C, Vitamin E, or other high potency vitamins
  • laxatives such as mineral oil or Ex Lax
  • antacids such as Maalox, Mylanta, or Gelusil with or just before taking warfarin

You can use:

  • Low dose acetaminophen (Tylenol). Note: The amount of acetaminophen should be as low as possible and monitored carefully. High doses of acetaminophen can prolong the INR.
  • Milk of Magnesia or Colace
  • A general multivitamin that does not contain more than 100% RDA of various components and does not contain Vitamin K

Side Effects

The primary side effect of warfarin is excessive bleeding. Notify your physician if you develop:

  • red, dark, or cloudy urine
  • bloody stools or black, tarry stools
  • bleeding from gums or nose
  • unexpected bruising
  • excessive bleeding from minor cuts (bleeding doesn't stop after 10 to 15 minutes)
  • excessive menstrual bleeding
  • vomiting blood or "coffee ground" like material
  • coughing up blood
  • visual changes or loss of vision
  • weakness or loss of sensation

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