Understanding Coumadin

What is Coumadin?

Coumadin (warfarin) is a blood thinner and it reduces the formation of blood clots.

Coumadin is used to prevent blood clots, heart attacks, and strokes.

What should you know before taking Coumadin?

You should not take Coumadin if you are allergic to warfarin, or if you have:

  • hemophilia or any bleeding disorder that is inherited or caused by disease
  • a blood cell disorder (such as low red blood cells or low platelets)
  • blood in urine or stools, or if you have been coughing up blood
  • an infection of the lining of your heart (bacterial endocarditis)
  • stomach or intestinal bleeding or ulcer
  • recent head injury, aneurysm, or bleeding in the brain; or
  • undergone a spinal tap or spinal anesthesia (epidural)

Coumadin shouldn’t be prescribed if you cannot be reliable in taking it because of alcoholism, psychiatric problems, dementia, or similar conditions.

Coumadin can make you bleed more easily, especially if you have:

  • a history of bleeding problems
  • high blood pressure
  • severe heart disease
  • kidney or liver disease
  • cancer
  • a disease affecting the blood vessels in the brain
  • a history of stomach or intestinal bleeding
  • a surgery or medical emergency, or if any type of injection is given
  • 65 or older

To make sure Coumadin is safe for you, tell your doctor if you have:

  • an intestinal disorder
  • diabetes
  • congestive heart failure
  • overactive thyroid
  • recent or upcoming surgery on your brain, spine, or eye
  • a connective tissue disorder such as Marfan Syndrome, Sjogren syndrome, scleroderma, rheumatoid arthritis, or lupus
  • a hereditary clotting deficiency (warfarin may make your symptoms worse at first)
  • if you use a catheter
  • if you have ever had low blood platelets after receiving heparin

Do not use Coumadin if you are pregnant, unless your doctor tells you to. Coumadin can cause birth defects, but preventing blood clots in certain women may outweigh any risks to the baby. Use effective birth control to prevent pregnancy during treatment. It is not known whether warfarin passes into breast milk or if it could harm a nursing baby.

How to properly take Coumadin

Take Coumadin exactly as prescribed by the doctor and follow all directions on the prescription label. Doctors may occasionally change dosage to provide the best results. Do not take Coumadin in larger or smaller amounts or for longer than the doctor prescribes.

Take Coumadin at the same time every day, with or without food. Never take a double dose of this medicine.

While using Coumadin, frequent “INR” or prothrombin time tests (to measure how long it takes your blood to clot) will be given. You may not notice any change in the symptoms, but your blood work will help the doctor determine how long to continue the treatment. You must remain under the care of a doctor while using this medicine.

If you have received Coumadin in a hospital, call or visit your doctor 3 to 7 days after you leave the hospital. Your INR will need to be tested at that time and do not miss any follow-up appointments.

Tell the doctor if you are sick with diarrhea, fever, chills, or flu symptoms, or if you experience weight changes.

You may need to stop taking warfarin 5 to 7 days before having any surgery or dental work. Call the doctor for instructions. You may also need to stop taking warfarin for a short time if you need to take antibiotics.

Wear a medical alert tag or carry an ID card stating that Coumadin is prescribed to you. Any medical care provider who treats you should know that you are using this medicine.

What are the side effects of coumadin?

Your doctor should be notified if you experience any of these symptoms:


Less common


  • Abdominal or stomach pain with cramping
  • bleeding gums
  • blood in the urine
  • bloody stools
  • blurred vision
  • burning, crawling, itching, numbness, prickling, “pins and needles”, or tingling feelings
  • chest pain or discomfort
  • confusion
  • coughing up blood
  • difficulty with breathing or swallowing
  • dizziness, faintness, or lightheadedness after getting up
  • excessive bruising
  • headache
  • increased menstrual flow or vaginal bleeding
  • nosebleeds
  • paralysis
  • peeling of the skin
  • prolonged bleeding from cuts
  • red or black, tarry stools
  • red or dark brown urine
  • shortness of breath
  • sweating
  • unexplained swelling
  • unusual tiredness or weakness



  • Arm, back, or jaw pain
  • blue-green to black skin discoloration
  • blue or purple toes
  • change in consciousness
  • chest tightness or heaviness
  • chills
  • clay-colored stools
  • diarrhea
  • dizziness
  • fainting or loss of consciousness
  • fast or irregular breathing or heartbeat
  • fever
  • itching
  • light-colored stools
  • loss of appetite
  • nausea and vomiting
  • pain in the toes
  • pain, redness, or sloughing of the skin
  • pale skin
  • skin blisters
  • skin rash
  • small red or purple spots on the skin
  • stomach pain
  • swelling of the eyes or eyelids
  • tightness in the chest or wheezing
  • troubled breathing with exertion
  • unpleasant breath odor
  • unusual bleeding or bruising
  • upper right abdominal or stomach pain
  • vomiting of blood
  • yellow eyes and skin


Incidence not known


  • Painful or prolonged erection of the penis


Some side effects do not need medical attention and as the body adjusts to Coumadin the following side effects will fade away.


Less common


  • Joint pain
  • muscle pain




  • Bloated
  • change in taste, or bad, unusual, or unpleasant (after) taste
  • cold intolerance
  • excess air or gas in the stomach or intestines
  • full feeling
  • general feeling of discomfort or illness
  • hair loss or thinning of the hair
  • hives or welts
  • lack or loss of strength
  • pain
  • passing gas
  • red, sore, or itching skin
  • sores, welting, or blisters
  • unusual drowsiness, dullness, or feeling of sluggishness

What happens if you miss a dose of coumadin?

Take the missed dose as soon as you can. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra dose to make up for the dose that was missed.

What happens if you overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222. Overdose can cause excessive bleeding.

What should you avoid if you take Coumadin?

Avoid activities that increase the risk of bleeding or injury. Use extra care to prevent bleeding while shaving or brushing your teeth. It is possible to bleed more easily for several days after quitting Coumadin.

Ask the doctor before taking any medicine for pain, arthritis, fever, or swelling. This includes Tylenol, aspirin, Advil, Motrin, Aleve, Celebrex, diclofenac, indomethacin, meloxicam, and others. These medicines can affect blood clotting and may also increase the risk of stomach bleeding.

Avoid making any changes in your diet without first talking to your doctor. Foods that are high in vitamin K can make Coumadin less effective. Grapefruit juice may interact with Coumadin and lead to unwanted side effects. Avoid the use of grapefruit products while taking Coumadin.