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Warfarin Toxicity

Medically reviewed by Last updated on Oct 31, 2022.

What is warfarin toxicity?

Warfarin toxicity happens when you have too much warfarin in your body. Certain changes to foods and medicines can also increase the effect of warfarin. Warfarin is a medicine that is used to prevent or treat the formation of blot clots. It works by making your blood clot more slowly. Warfarin toxicity can cause bleeding that can become life-threatening.

What increases my risk for warfarin toxicity?

  • You take higher doses of warfarin than is recommended by your healthcare provider.
  • Your risk of warfarin toxicity increases if you do not have your INR checked as recommended. Your healthcare provider adjusts your dose based on your INR. The INR, or International Normalized Ratio, is a measure of how long it takes your blood to clot. Your risk of bleeding increase over time when your INR is too high.
  • A sudden decrease of vitamin K in your diet can increase your risk of bleeding. Vitamin K changes how your blood clots. Your vitamin K levels affect your INR.
  • You start or stop taking another medicine or supplement that affects the way warfarin works.

What are the signs and symptoms of warfarin toxicity?

  • Red spots on your skin that look like a rash
  • Severe headache or dizziness
  • Heavy bleeding after an injury
  • Heavy bleeding during monthly period in women
  • You have severe stomach pain or you vomit blood
  • Pink, red, or dark brown urine
  • Black or bloody bowel movements

How do I safely take warfarin?

  • Go to all your follow-up appointments. Your healthcare provider will need to monitor you closely while you are taking warfarin. Your provider may need to adjust your dose based on your INR results.
  • Take this medicine exactly as directed. Contact your healthcare provider if you miss a dose or you have any questions about how to take warfarin.
  • Do not start or stop taking medicines or herbal supplements that can affect the way that warfarin works. Some examples include NSAIDs, aspirin, acetaminophen, and certain antacids, antibiotics, and medicines used to lower cholesterol. Some herbal supplements that can affect the way warfarin works are ginkgo biloba, garlic, fish oil, vitamin E, and tumeric. Talk to your healthcare provider before you start or stop any medicines.
  • Eat the same amount of vitamin K daily to help keep your INR stable. Vitamin K is found in green leafy vegetables, broccoli, grapes, and other foods. Ask your healthcare provider for more information about vitamin K.
    Vitamin K Sources
  • Avoid alcohol. Alcohol increases your INR.

What else should I do while I am taking warfarin?

Wear medical alert jewelry or carry a card that says you take warfarin. Ask where to get these items.

Medical Alert Jewelry

What should I do if I think I or someone I know took too much warfarin?

Call the Poison Control Center at 1-800-222-1222 immediately.

When should I seek immediate care?

  • You have a severe headache or dizziness.
  • You have heavy bleeding that does not stop.
  • You have severe stomach pain or you vomit blood.
  • Your urine is pink, red, or dark brown.
  • You have black or bloody bowel movements.

When should I contact my healthcare provider?

  • You have fever and chills.
  • Your gums bleed when you brush your teeth.
  • You have frequent nosebleeds.
  • You bruise easily.
  • You have red spots on your skin that look like a rash.
  • You have heavy bleeding during your period if you are a woman.
  • You have questions or concerns about your condition or care.

Care Agreement

You have the right to help plan your care. Learn about your health condition and how it may be treated. Discuss treatment options with your healthcare providers to decide what care you want to receive. You always have the right to refuse treatment. The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.

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