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.

You’ve been prescribed warfarin because your body may be making blood clots, or you may have a medical condition known to promote them. It’s often prescribed for folks with atrial fibrillation (an irregular heart rhythm), pulmonary embolism (blockage of a major blood vessel in the lung), and after artificial heart valve surgery or an orthopedic procedure like hip replacement or other types of bone surgery.

Blood clots can move to other parts of your body and cause serious medical problems, such as a heart attack. 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 given in a pill include:

Blood Testing and Blood Thinners

So that your doctor will know the correct dose of warfarin to give you, 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 him. This will help him figure out if he needs to change your warfarin therapy.

What Does Warfarin Look Like?

The tablets are round and scored, which means they can be broken in half. Each tablet color represents a different strength:

  • 1 milligram (pink)
  • 2 milligrams (lavender)
  • 2.5 milligrams (green)
  • 3 milligrams (tan)
  • 4 milligrams (blue)
  • 5 milligrams (peach)
  • 6 milligrams (teal or blue-green)
  • 7.5 milligrams (yellow)
  • 10 milligrams (white)

The brands should have the same colors and strengths. However, some brands may have a different shape or appearance. For example, they may be oval or square.


How Should I Take It?

Take your dose as instructed once daily. Try to take it at the same time each day. It’s best to take it 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 dose. Also, never change how much you take without first discussing it with your doctor.

How Should I Store It?

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

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

What Precautions Should I Take?

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.

Manymedications and dietary supplementscan affect the way warfarin works. These may include:

Before taking 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. He may need to change your dosage. Or he may recommend another medication less likely to interfere with warfarin.

Some foods can affect warfarin. Follow these guidelines:

  • 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.


A few day-to-day things can be risky:

  • Check with your doctor before starting any exercise or sports program. Your doctor may want you to avoid any activity or sport that may cause a serious fall or other injury.
  • Use a soft toothbrush. Brush and floss gently so your gums won't bleed.
  • Be careful when using razors. If you cut yourself, follow the guidelines below.

Illness and emergencies can have a big impact. Things can pop up. When they do, be smart:

  • If you cut yourself and the cut is 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 the cut is 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.
  • It is recommended that you wear or carry identification that says you are taking warfarin.
  • Avoid situations that may injure you at home or at work.

If you are taking warfarin and planning to become pregnant, talk with your doctor about the possible risks and ways to lower them. Tell your doctor right away if you become pregnant, since warfarin can have serious effects on your baby.

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.

Check with your doctor before you hit the road. You may need to have a blood test, and your warfarin dose may need to be 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.


When Should I Call my Doctor?

If you notice any of the following signs of bleeding or illness, pick up the phone. They can affect the way warfarin works:

  • Weakness or more fatigue than usual, or looking pale (symptoms of anemia)
  • Cuts that won't stop bleeding after pressure is applied for 10 minutes
  • Coughing or vomiting blood (which may look like coffee grounds)
  • Blood from the nose, gums, or ears
  • Unusual color of the urine or stool (including dark brown urine, or red or black, tarry stools)
  • Unusual bruising (black and blue marks on your skin) for unknown reasons
  • Menstrual bleeding that is heavier or lasts longer than normal
  • A fever or illness that gets worse
  • A serious fall or a blow to the head
  • Unusual pain or swelling
  • Unusual headache
  • Dizziness
  • Difficulty breathing

If you notice any of these, your doctor may want to do a blood test, stop the warfarin, or prescribe meds to stop the bleeding.

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

WebMD Medical Reference Reviewed by James Beckerman, MD, FACC on August 17, 2017




National Institutes of Health. 


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