Warfarin - overview

Brand names: Coumadin, Marevan

Warfarin is a medicine that affects blood clotting. It is a type of anticoagulant medicine.

Warfarin is mainly used to prevent certain types of blood clots for people who are at risk of blood clots or who already have a blood clot (thrombus). (Read more about the different types of blood clots and when warfarin is used). Such clots can cause conditions like stroke in people with atrial fibrillation, or venous thromboembolism (VTE) in people who’ve had certain surgical procedures. These conditions can be life-threatening if action is not taken to prevent them.

Living with warfarin

Libby has found taking warfarin for pulmonary embolism (PE) and, later, atrial fibrillation (AF) fairly straightforward. She talks about INR testing and adjusting the dose.


Warfarin is a very effective medicine used by thousands of people. However if you take warfarin, it is important that you use it safely and correctly, because bleeding is one of its main side effects. Living with warfarin means you will need to follow special steps to reduce your risk of bleeding.

These include:

  • having regular blood tests to see how much your blood is clotting
  • taking the exact dose of warfarin your doctor has prescribed
  • sticking to the same brand of warfarin
  • checking with your doctor or pharmacist before you use any other medicines, including non-prescription and complementary medicines such as herbs and vitamins that may cause interactions
  • keeping your diet consistent — especially your intake of foods that are rich in vitamin K (e.g. vegetables with dark green leaves and those from the cabbage family)
  • limiting the amount of alcohol you drink to no more than 1–2 standard drinks per day
  • limiting the amount of cranberry juice you drink
  • telling all of your healthcare providers, including your dentist, that you are taking warfarin
  • being aware of the different signs of bleeding — such as bleeding gums, red or black bowel motions, easy bruising — so you can report them to your doctor
  • seeing your doctor if you become unwell – stomach upsets or being sick can sometimes effect your INR, especially if you don’t eat normally
  • wearing a MedicAlert ID stating that you are taking warfarin.

This section answers some questions you may have about warfarin (the active ingredient in the brands Coumadin and Marevan). It provides important information you need to know on how to take warfarin correctly and safely. If you are unsure about anything or need more information about your medical condition, speak to your health professional.

Use the NPS Warfarin Dose Tracker to help you keep track of your INR results and your daily warfarin dose. Download or order a free copy, or have a copy sent to you by calling us on (02) 8217 8700.

Download our Living well with warfarin fact sheet — for people who’ve been prescribed warfarin, or their carers, to help you live safely with warfarin. The more you know about warfarin, the more your health will benefit.

Phone for medicines information

Call NPS Medicines Line on 1300 MEDICINE (1300 633 424) to get information about your prescription, over-the-counter and complementary medicines (herbal, ‘natural’, vitamins and mineral supplements) from a pharmacist. Your call will be answered by healthdirect Australia.

References