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Your Guide to Coumadin®/Warfarin Therapy

Coumadin®/warfarin is a medicine that helps your blood flow easier and not clot. Your Guide to Coumadin®/Warfarin Therapy explains what to expect and what to watch out for during therapy.

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What Coumadin®/Warfarin Is and What It Does for You
How to Take Coumadin®/Warfarin
Blood Tests
Possible Side Effects
Stay Safe While Taking Coumadin®/Warfarin
Use of Other Medications
Diet for Coumadin®/Warfarin Users
Share Information With Your Other Doctors
Medical Conditions
   Blood clots
   Blood clots in the lung
   Heart attack
   Heart valve disease
   Heart valve replacement
   Irregular heartbeat
Acknowledgments, Disclaimer, and Licensing



Your doctora has started you on the medication Coumadin® (generic name: warfarin). Patients who are on Coumadin®/warfarin must be watched closely. You will need to have blood drawn often. You will also need to be careful that you do not do something to hurt yourself and cause bleeding.Your doctor will work with you to keep you healthy and safe while you are taking Coumadin®/warfarin.

Starting on a new medicine, especially one you may have to take for a long period of time, may make you worry. To help you learn about your medication, your doctor has given you this booklet to take home and read. The information in the booklet will help you understand why you are taking Coumadin®/warfarin and how to keep yourself healthy. Please take time to read all of the information in the booklet.


Call your doctor if you have questions.

  • Your doctor's phone number is: ______________________________________________________
  • Your pharmacy's phone number is: ______________________________________________________

You can stay healthy even when you have a health problem that needs special medication. You and your doctor will work together as a team to make sure that taking a medication like Coumadin®/warfarin does not stop you from living well and safely.

a  In this booklet, the term “doctor” is used. It can mean doctor, nurse, physician's assistant, nurse practitioner, pharmacist, or other heath care professional.

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What Coumadin®/Warfarin Is and What It Does for You

If your blood is too thick and forms clots, you could be at risk for heart attack, stroke, and other serious medical problems. Coumadin®/warfarin is a medicine that helps prevent blood clots. The drug is an anticoagulant. "Anti" means against and "coagulant" means to thicken into a gel or solid. Sometimes this drug is called a blood thinner. Think of syrup being poured—it is sticky and thick and flows slowly. Coumadin®/warfarin helps your blood flow easier and not clot.

Some people are more likely to get blood clots. Talk to your doctor to find out if you are at risk.

Coumadin®/warfarin will:

  • Keep your blood from making clots.
  • Help your blood flow more easily.

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How to Take Coumadin®/Warfarin

Always take your pills as directed. You must take the pills only on the days your doctor tells you to. The amount of Coumadin®/warfarin each person needs is different. The dose is based on a blood test called the INR (International Normalized Ratio). The amount of medication you take may change, based on the blood test. It needs to be taken at the same time, usually in the evening.

Coumadin®/warfarin can be taken with other medications. Never skip a dose, and never take a double dose. If you miss a dose, take it as soon as you remember.

If you don't remember until the next day, please call your doctor for instructions. If this happens on a weekend or holiday, skip the missed dose and start again the next day. Mark the missing dose in a diary. A daily pillbox will help you keep track of your dose.


  • Go for blood tests as directed.
  • Never skip a dose.
  • Never take a double dose.
  • Take Coumadin®/warfarin at the same time as directed by your doctor.

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Blood Tests

The doctor decides how much Coumadin®/warfarin you need by testing your blood. The test measures how fast your blood is clotting and lets the doctor know if your dosage should change. If your blood test is too high, you might be at risk for bleeding problems. If it is too low, you might be at risk for forming clots. Your doctor has decided on a range on the blood test that is right for you.

Regulating your blood with Coumadin®/warfarin is like balancing a scale. If you take too much you will increase bleeding; if you take too little, your blood will clot. Getting your blood within the target range is getting it balanced.

When you first start taking Coumadin®/warfarin you may have your blood checked often. Once the blood test is in the target range and the correct dose is reached, this test is done less often. Because your dose is based on the INR blood test, it is very important that you get your blood tested on the date and at the time that you are told.

Illness can affect your INR blood test and your Coumadin®/warfarin dose. If you become sick with a fever, the flu, or an infection, call your doctor. Also call if you have diarrhea and vomiting lasting more than 1 day.

Know your INR blood test range

My INR blood test range is: ______________________________________________________________

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Possible Side Effects

Side effects with Coumadin®/warfarin may happen. Side effects may include bleeding. To lower the risk of bleeding, your blood Coumadin®/warfarin level will be kept within a range that is right for you. Even when your INR blood test is in range, you might see a little bleeding like bruises on your body or slight gum bleeding when you brush your teeth. Some people may experience hair loss or skin rashes, but this is rare. If you notice something wrong that you feel may be caused by your medication, call your doctor.

Slight bleeding—you may notice from time to time:

  • Gum bleeding while brushing teeth.
  • Occasional nosebleed.
  • Easy bruising.
  • Bleeding after a minor cut that stops within a few minutes.
  • Menstrual bleeding that is a little heavier than normal.

Major bleeding—call your doctor, or go to the hospital emergency room if you have any of the following:

  • Red, dark, coffee or cola colored urine.
  • Bowel movements that are red or look like tar.
  • Bleeding from the gums or nose that does not stop quickly.
  • Vomit that is coffee colored or bright red.
  • Anything red in color that you cough up.
  • Severe pain, such as a headache or stomachache.
  • Sudden appearance of bruises for no reason.
  • Menstrual bleeding that is much heavier than normal.
  • A cut that will not stop bleeding within 10 minutes.
  • A serious fall or hit on the head.
  • Dizziness or weakness.

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Stay Safe While Taking Coumadin®/Warfarin

You will need to be careful using objects, such as knives and scissors, that could make you bleed. You will need to avoid some activities and sports that could cause injury. For example, it is not a good idea to take up risky sports while you are on Coumadin®/warfarin. This does not mean you cannot do the things that you enjoy. If you like to work in the yard, be sure to wear sturdy shoes and gloves. Activities that would be safe for you include swimming and walking.

It is very important to know that you can be bleeding and not see any blood. For example, you could fall and hit your head, and bleeding could occur under your skull. Or, you could fall and hurt your arm and notice a large purple bruise. This would be bleeding under the skin. Call your doctor or go to the hospital immediately if you have taken a bad fall, even if you are not bleeding.

Talk to your doctor about wearing a medical alert bracelet or necklace. If you are badly injured and unable to speak, the bracelet would tell health care workers that you are on Coumadin®/warfarin.

Stay Active

Exercise is important to your health. Think about the sports and activities you like doing. Do they put you at risk for injury? For example, if you like to ride your bike, be sure you wear a helmet and gloves. If you would like to start a new activity that will increase the amount of exercise you get every day, talk to your doctor.

To prevent injury indoors:

  • Be very careful using knives and scissors.
  • Use an electric razor.
  • Use a soft toothbrush.
  • Use waxed dental floss.
  • Do not use toothpicks.
  • Wear shoes or non-skid slippers in the house.
  • Take care trimming your toenails.
  • Do not trim corns or calluses yourself.

To prevent injury outdoors:

  • Always wear shoes.
  • Wear gloves when using sharp tools.
  • Avoid activities and sports that can easily hurt you.
  • Wear gardening gloves when doing yard work.

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Use of Other Medications

When Coumadin®/warfarin is taken with other medicines it can change the way other medicines work. Other medicines can also change the way Coumadin®/warfarin works. It is very important to talk with your doctor about all of the other medicines that you are taking, including over-the-counter medicines, antibiotics, vitamins, or herbal products.

Any product containing aspirin may lessen the blood's ability to form clots and may harm you when you take Coumadin®/warfarin. If you take a daily aspirin, talk with your doctor about what dose is right for you.

Other medicines you get over-the-counter may have aspirin in them. All medications must be approved by your doctor, including medicines you have taken before you started Coumadin®/warfarin. Following is a list of some common medications that should be approved by your doctor.

Pain relievers, such as:

  • Excedrin®.
  • Acetaminophen (Tylenol®).
  • Naproxen (Aleve®).
  • Ibuprofen (Advil®, Motrin®, Nuprin®, Midol®, Pamprin HB®).

Stomach remedies, such as:

  • Cimetidine (Tagamet HB®).
  • Bismuth Subsalicylate (Pepto Bismol®).
  • Laxatives and stool softeners.
  • Alka-Seltzer®.

Herbal products, such as:

  • Garlic.
  • Green tea.
  • Ginkgo.


Check the Coumadin®/warfarin you are taking. Does the medicine seem different from what your doctor wrote on the prescription or look different from what you expected? Does your refill look different than what you used before? Is the color the same as what you were previously given? If something seems different, ask the pharmacist to double-check it. Most errors are first found by patients.

Medicines look different: Coumadin® pills (upper row) and generic warfarin (lower row)

Picture of various brands of Coumadin(R) and generic warfarin that are in different colors. Nine Coumadin(R) pills are on the upper row, nine generic warfarin pills are on the lower row.


Check Your Medicine

Always tell your doctor about all the medicines you are taking. Tell your doctor when you start taking new medicine and when you stop. Bring a list of current medications, over-the-counter drugs—such as aspirin—and any vitamins and herbal products you take.

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Diet for Coumadin®/Warfarin Users

The foods you eat can affect how well Coumadin®/warfarin works for you. High amounts of vitamin K might work against Coumadin®/warfarin. Talk to your doctor about the amount of vitamin K that is right for you.

These foods contain vitamin K:

Fruits and vegetables, such as:

  • Kiwi.
  • Blueberries.
  • Broccoli.
  • Cabbage.
  • Brussels sprouts.
  • Green onions.
  • Asparagus.
  • Cauliflower.
  • Peas.
  • Lettuce.
  • Spinach.
  • Turnip, collard, and mustard greens.
  • Parsley.
  • Kale.
  • Endive.

Meats, such as:

  • Beef liver.
  • Pork liver.


  • Mayonnaise.
  • Margarine.
  • Canola oil.
  • Soybean oil.
  • Vitamins.
  • Soybeans.
  • Cashews.

Keep Your Diet the Same

Do not make any major changes in your diet or start a weight loss plan without calling your doctor.

Call your doctor if you are unable to eat for several days, for whatever reason. Also call if you have stomach problems, vomiting, or diarrhea that lasts more than 1 day. These problems could affect your Coumadin®/warfarin dosage.

Limit alcohol. Alcohol can affect your Coumadin®/warfarin dosage but it does not mean you must avoid all alcohol. Serious problems can occur with alcohol and Coumadin®/warfarin when you drink more than 2 drinks a day or when you change your usual pattern. Binge drinking is not good for you. Be careful on special occasions or holidays, and drink only what you usually would on any regular day of the week.

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Share Information With Your Other Doctors

Because you are on Coumadin®/warfarin you will be seen regularly by the doctor who ordered your medication. You may also see other doctors regularly to keep yourself healthy. When you see other doctors, it is very important that you tell them you are taking Coumadin®/warfarin. You should also tell your dentist and the person who cleans your teeth. If another doctor orders a new medication for you, please call the doctor who ordered your Coumadin®/warfarin so it can be noted in your file.

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Medical Conditions

If you have any of the following medical conditions or are at risk for having them, your doctor may have given you a prescription for Coumadin®/warfarin.

Blood clots. Blood clots (deep vein thrombosis) form in a vein. The veins deep inside your leg, especially the calf and thigh, are the most common areas where clots occur. Blood clots can lead to damage of the blood vessels in your leg.


  • Decreases the chance of blood clotsin the veins of your legs.
  • Lowers your risk for blood clots.

Blood clots in the lung. A blood clot that forms in another part of your body, such as in your leg, can break loose and move through the blood to your lungs. The clot then gets stuck within a blood vessel that brings blood to the lungs (called a pulmonary embolism). If the lungs cannot get enough blood, they will be damaged, and you will have difficulty breathing.


  • Decreases the chance of blood clots.
  • Lowers your risk of a blood clot in the lung.

Heart attack. A heart attack is caused by a lack of blood supply to the heart. The lack of blood happens when one or more of the blood vessels pumping blood to the heart are blocked.


  • Decreases the chance of blood clots.
  • Helps blood flow easier.

Heart valve disease. Heart valve disease is any problem in one or more of the four valves in the heart. Heart valves keep blood flowing in one direction. They act as a door that swings open, allowing blood to flow through the sections of the heart. When heart valves are not working like they should, blood flow can become slowed and clots can form.


  • Decreases the chance of blood clots.
  • Helps blood flow easier.

Heart valve replacement. There are many types of artificial valves that are used to replace your own heart valve. The material used to make these valves may cause blood to stick and form clots.


  • Decreases the chance of blood clots around a heart valve.
  • Decreases the chance of blood clots.

Irregular heartbeat. Irregular heartbeat (atrial fibrillation) is a fairly common heart disorder. Sometimes your heart will beat too fast or out of rhythm and may cause blood clots.


  • Decreases the chance of blood clots.
  • Helps blood flow more easily.

Stroke. A stroke is caused by a blood clot that blocks a blood vessel in the brain. This blockage cuts off the blood flow to a part of the brain and can cause problems with your speech, swallowing, or movement of different parts of your body. You may be at a higher risk for a stroke if you've had a heart attack.


  • Decreases the chance of blood clots in the blood vessels of your brain.
  • Lowers your risk for a stroke after a heart attack.

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Acknowledgments, Disclaimer, and Licensing

This booklet is based on a product developed by Carla Huber, A.R.N.P., M.S., Cedar Rapids Community Anticoagulation Clinic, Cedar Rapids, Iowa (, under Agency for Healthcare Research and Quality (AHRQ) Grant No. 1 U18 HSO15830-01 to Kirkwood Community College.

This document is in the public domain and may be used and reprinted without special permission. Citation of the source is appreciated.

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AHRQ Publication No. 08-0028-A
Revised August 2008

Internet Citation:

Your Guide to Coumadin®/Warfarin Therapy. AHRQ Publication No. 08-0028-A, August 2008. Agency for Healthcare Research and Quality, Rockville, MD.


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