Your Guide to 

Coumadin®

/Warfarin 

Therapy
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 (chuber@pcofiowa.com), 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. 

Notes:

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How to Order AHRQ Booklets

For more copies of this booklet, e-mail the AHRQ Publications Clearinghouse

at AHRQPubs@ahrq.hhs.gov or call the toll-free number: 800-358-9295.

For other consumer and patient materials, go to the AHRQ Web site at:

www.ahrq.gov/consumer.
1

Contents

Introduction............................................................................................2

What Coumadin®

/Warfarin Is and What It Does for You........................3

How to Take Coumadin®

/Warfarin .........................................................3

Blood Tests..............................................................................................4

Possible Side Effects ................................................................................5

Stay Safe While Taking Coumadin®

/Warfarin...........................................6

Use of Other Medications .......................................................................8

Diet for Coumadin®

/Warfarin Users ......................................................10

Share Information With Your Other Doctors........................................11

Medical Conditions ...............................................................................12

Blood Clots.................................................................................................12

Blood Clots in the Lung.............................................................................12

Heart Attack ...............................................................................................12

Heart Valve Disease ....................................................................................13

Heart Valve Replacement............................................................................13

Irregular Heartbeat.....................................................................................13

Stroke..........................................................................................................13

Warning!

Doctors warn against taking Coumadin®

/warfarin if you are

pregnant or planning to get pregnant. Coumadin®

/warfarin may

cause birth defects or bleeding that may harm or even lead to

the death of your unborn child.
2

Introduction 

Your doctor* 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. 

Reminders:

Call your doctor if you have questions. 

■ Your doctor’s phone number is: 

_________________________________________

■ Your pharmacy phone number is: 

_________________________________________

You can stay healthy even when you have a medical condition 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.

*In this booklet, the term “doctor” is used. It can mean doctor, nurse, physician’s assistant,

nurse practitioner, pharmacist, or other heath care professional.
3

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

more easily 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. 

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. 
4

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.

Checklist: 

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. 

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.
5

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: 

________________________

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. 
6

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. 

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.
7

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. 
8

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.

Vitamins
9

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.

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.

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

(lower row)
10

Other:

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.
11

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.

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.
12

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. 

Coumadin®

/warfarin:

■ Decreases the chance of blood clots in 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.

Coumadin®

/warfarin:

■ 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.

Coumadin®

/warfarin:

■ Decreases the chance of blood clots. 

■ Helps blood flow more easily.
13

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.

Coumadin®

/warfarin:

■ Decreases the chance of blood clots. 

■ Helps blood flow more easily.

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.

Coumadin®

/warfarin:

■ 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.

Coumadin®

/warfarin:

■ Decreases the chance of blood clots. 

■ Helps the 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.

Coumadin®

/warfarin:

■ Decreases the chance of blood clots in the blood vessels of your brain.

■ Lowers your risk for a stroke after a heart attack.
U.S. Department of

Health and Human Services

Public Health Service

Agency for Healthcare Research and Quality

540 Gaither Road

Rockville, MD 20850

AHRQ Pub. No. 08-0028-A

Revised August 2008

www.ahrq.gov