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Taking warfarin

Show Alternative Names
Anticoagulant care
Blood-thinner care

Warfarin is a medicine that makes your blood less likely to form clots. It is important that you take warfarin exactly as you have been told. Changing how you take your warfarin, taking other medicines with it or at different times, and eating certain foods can change the way warfarin works in your body. If this happens, you may be more likely to form a clot or have bleeding problems.

What to Expect at Home

Warfarin is a medicine that makes your blood less likely to form clots. This may be important if:

  • You have already had blood clots in your leg, arm, heart, or brain.
  • Your health care provider is worried that a blood clot may form in your body. People who have a new heart valve, a large heart, a heart rhythm that is not normal, or other heart problems may need to take warfarin.

When you are taking warfarin, you may be more likely to bleed, even from activities you have always done.

Changing how you take your warfarin, taking other medicines, and eating certain foods all can change the way warfarin works in your body. If this happens, you may be more likely to form a clot or have bleeding problems.

Taking Warfarin

It is important that you take warfarin exactly as you have been told.

  • Take only the dose your provider has prescribed. If you miss a dose, contact your provider for advice.
  • If your pills look different from your last prescription, contact your provider or pharmacist right away. The tablets are different colors, depending on the dose. The dose is also marked on the pill.

Your provider will test your blood at regular visits. This is called an INR test or sometimes a PT test. The test helps make sure you are taking the right amount of warfarin to help your body.

Alcohol and some medicines can change how warfarin works in your body.

  • DO NOT drink alcohol while you are taking warfarin.
  • Talk with your provider before taking any other over-the-counter medicines, vitamins, supplements, cold medicines, antibiotics, or other medicines.

Tell all of your providers that you are taking warfarin. This includes doctors, nurses, and your dentist. Sometimes, you may need to stop or take less warfarin before having a procedure. Always talk to the provider who prescribed the warfarin before stopping or changing your dose.

Ask about wearing a medical alert bracelet or necklace that says you are taking warfarin. This will let providers who take care of you in an emergency know that you are taking this medicine.

Your Diet

Some foods can change the way warfarin works in your body. Make sure you check with your provider before making any big changes in your diet.

You do not have to avoid these foods, but try to eat or drink only small amounts of them. At the least, do not change the amount of these foods and products you eat day-to-day or week-to-week:

  • Mayonnaise and some oils, such as canola, olive, and soybean oils
  • Broccoli, Brussels sprouts, and raw green cabbage
  • Endive, lettuce, spinach, parsley, watercress, garlic, and scallions (green onions)
  • Kale, collard greens, mustard greens, and turnip greens
  • Cranberry juice and green tea
  • Fish oil supplements
  • Herbs used in herbal teas

Other Tips

Because being on warfarin can make you bleed more than usual:

  • You should avoid activities that could cause an injury or open wound, such as contact sports.
  • Use a soft toothbrush, waxed dental floss, and an electric razor. Be extra careful around sharp objects.

Prevent falls in your home by having good lighting and removing loose rugs and electric cords from pathways. Do not reach or climb for objects in the kitchen. Put things where you can get to them easily. Avoid walking on ice, wet floors, or other slippery or unfamiliar surfaces.

Make sure you look for unusual signs of bleeding or bruising on your body.

  • Look for bleeding from the gums, blood in your urine, bloody or dark stool, nosebleeds, or vomiting blood.
  • Women need to watch for extra bleeding during their period or between periods.
  • Dark red or black bruises may appear. If this happens, call your provider right away.

When to Call the Doctor

Contact your provider if you have:

  • A serious fall, or if you hit your head
  • Pain, discomfort, swelling at an injection or injury site
  • A lot of bruising on your skin
  • A lot of bleeding (such as nosebleeds or bleeding gums)
  • Bloody or dark brown urine or stool
  • Headache, dizziness, or weakness
  • A fever or other illness, including vomiting, diarrhea, or infection
  • You become pregnant or are planning to become pregnant
Review Date: 1/1/2025

Reviewed By

Michael A. Chen, MD, PhD, Associate Professor of Medicine, Division of Cardiology, Harborview Medical Center, University of Washington Medical School, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

References

Becker RC, Ortel TL. Antithrombotic and antiplatelet therapy. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 70.

Jaffer IH, Weitz JI. Anticoagulant therapy. In: Sidawy AN, Perler BA, eds. Rutherford's Vascular Surgery and Endovascular Therapy. 10th ed. Philadelphia, PA: Elsevier; 2023:chap 41.

Kager L, Evans WE. Pharmacogenomics and hematologic diseases. In: Hoffman R, Benz EJ, Silberstein LE, et al, eds. Hematology: Basic Principles and Practice. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 8.

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© 1997- A.D.A.M., a business unit of Ebix, Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

All content on this site including text, images, graphics, audio, video, data, metadata, and compilations is protected by copyright and other intellectual property laws. You may view the content for personal, noncommercial use. Any other use requires prior written consent from Ebix. You may not copy, reproduce, distribute, transmit, display, publish, reverse-engineer, adapt, modify, store beyond ordinary browser caching, index, mine, scrape, or create derivative works from this content. You may not use automated tools to access or extract content, including to create embeddings, vectors, datasets, or indexes for retrieval systems. Use of any content for training, fine-tuning, calibrating, testing, evaluating, or improving AI systems of any kind is prohibited without express written consent. This includes large language models, machine learning models, neural networks, generative systems, retrieval-augmented systems, and any software that ingests content to produce outputs. Any unauthorized use of the content including AI-related use is a violation of our rights and may result in legal action, damages, and statutory penalties to the fullest extent permitted by law. Ebix reserves the right to enforce its rights through legal, technological, and contractual measures.
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