Warfarin and Other Blood Thinners for Heart Disease

Warfarin (Coumadin) is an anticoagulant medication. This means it helps prevent clots from forming in the blood. Blood thinners treat some types of heart disease.

Your doctor may have prescribed warfarin because your body is making blood clots or you have a medical condition known to promote them. People with atrial fibrillation (an irregular heart rhythm), pulmonary embolism (blockage of a major blood vessel in the lung), and who have had artificial heart valve surgery or an orthopedic procedure like hip replacement or other types of bone surgery often take it.

Blood clots can move to other parts of your body and cause serious medical problems, such as a pulmonary embolism. Warfarin won’t dissolve a blood clot. However, over time, the blood clot may dissolve on its own. Warfarin may also prevent other clots from forming or growing.

There are other blood thinners you may be given in the hospital, or even at home for a short time. You get these either by vein (IV) or just under the skin:

Other blood thinners that come as a pill include:

Blood Testing and Blood Thinners

To figure out the correct dose of warfarin, you’ll need to have blood tests. They’re done in a lab, usually once a week to once a month, as directed by your doctor.

The prothrombin time (PT or protime) test will tell your doctor how fast your blood is clotting and whether your dose needs to be changed. Illness, diet, changes to your medicines, and physical activities may affect the results.

Tell your doctor if your health, medications (prescription and over-the-counter), or lifestyle is different from the last time you saw them. These could change the amount of warfarin you need.

What Does Warfarin Look Like?

The tablets are round and scored, which means they can be broken in half. You can tell the strengths by the colors:

But the tablet shape may be different, like oval or square, if you change brands.

How Should I Store It?

As with most drugs, at room temperature, away from extreme cold, heat, light, and moisture is best. Bathroom cabinets are usually NOT a good place for storing medications because of dampness.

All medications, including warfarin, should always be kept out of the reach of children and pets.

How Should I Take It?

Take your dose as instructed once daily. Try to take it at the same time each day, like early in the evening (such as between 5 and 6 p.m.). You can take warfarin with or without food.

Don’t take a double dose to make up for a missed one. Also, never change how much you take unless you’ve talked about it with your doctor.

It’s important that you follow the precautions below when taking warfarin. It’ll reduce the risk of side effects and make the medicine more effective.

Other Medications and Supplements

Many medications and dietary supplements can affect the way warfarin works. These include:

Before you take any new drug — including over-the-counter medications, herbal products, vitamins, nutritional supplements, or medication prescribed by another doctor or dentist — check with the doctor who monitors your warfarin. They may need to change your dosage. Or they may recommend another medication less likely to interfere with warfarin.

Check in with your doctor before you travel. You may need to have a blood test and get your dose adjusted. While traveling, carry your medications with you at all times. Don’t put medications in checked baggage, and don’t leave them in the car.

Foods and Drinks

Eat a sensible, well-balanced diet.

Talk with your doctor if you are planning any major dietary changes, such as following a weight-reducing diet or adding nutritional supplements.

Large amounts of food high in vitamin K (such as broccoli, spinach, and turnip greens) may change the way warfarin works. Try to keep the amount of these foods in your diet about the same from week to week.

It is best to avoid alcohol while taking warfarin. Alcohol interferes with its effectiveness.

Some herbal teas may cause clotting problems.

Avoid Cuts and Injuries

Check with your doctor before starting any exercise or sports program. Your doctor may want you to avoid activities that may cause a serious fall or other injury.

Wear or carry identification that says you’re taking warfarin.

Use a soft toothbrush. Brush and floss gently so your gums won’t bleed.

Be careful when using razors.

If you cut yourself and it’s small, apply constant pressure over the cut until the bleeding stops. This may take up to 10 minutes. If the bleeding doesn’t stop, continue to apply pressure and go to the emergency room.

If you cut yourself and it’s large, apply constant pressure and get help immediately, either by phone or at the emergency room. Call your doctor if you have any symptoms of illness like vomiting, diarrhea, infection, or fever. Illness can change the way warfarin works.

Before any surgery or dental work, tell all your doctors and dentists that you’re taking warfarin. Before having surgery or dental work, you may need to have a blood test, and you may need to stop taking warfarin for a few days. Do not stop taking warfarin without first getting information from the doctor who monitors your warfarin.


If you’re planning to get pregnant, talk with your doctor about the problems you could have and what you can do to have a baby safely.

Tell your doctor right away if you become pregnant while you’re taking warfarin, since the drug can have serious effects on your baby.

When Should I Call my Doctor?

If you notice any of the following signs of bleeding or illness, pick up the phone.

Your doctor may want to do a blood test, stop the warfarin, or prescribe medication to stop the bleeding.

Also contact your doctor if you have any other symptoms that cause concern.

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