How to take warfarin

Take warfarin at the same time every day

Older man with diary

Use a treatment card or diary to track your INR and warfarin dose.

Warfarin is usually taken once a day, around the same time each day, exactly as prescribed by your health professional. It can be taken with or without food. Warfarin tablets should be swallowed whole with a glass of water, and not crushed or chewed.

How much warfarin do I take?

A health professional will always tell you how much warfarin to take.

You will need to have blood tests called International Normalised Ratio (INR) tests to work out the correct dose for you. INR tests measure how fast your blood clots.

When you first start warfarin, your doctor may change your dose more often to find the dose that keeps your INR stable.

Watch our video, in which Dr John Worthington explains what to do when you start taking warfarin. For example, how to work with your doctor to get the dose right for you, how often you will need INR tests, and making sure you take your warfarin dose at the same time every day.

You must take the exact dose of warfarin your doctor prescribes. Your dose may be different on different days. Even if you have been taking warfarin for a while, your dose may change from time to time, according to your INR test results.

Warfarin tablets come in different strengths. More than one tablet strength may be prescribed to make up your daily dose. Each strength is a different colour. The colour of the different strength tablets also differs between brand.

Ensure you’re taking the right dose of your usual brand, as prescribed, by checking the tablet strength on the medicine label or packaging.

Ask your doctor or pharmacist if you are unsure of the dose or strength of tablet you need to take.

When will it start to work?

Warfarin can take a few days to start working. Because of this, your doctor may also briefly put you on another medicine — such as heparin or a related medicine like enoxaparin (Clexane) or dalteparin (Fragmin). Make sure you know when to start and stop these extra medicines.

Keep track of your daily dose

Because your dose may occasionally change, it is a good idea to keep a record of the dose you are currently taking and the date you were prescribed it.

If you accidentally take the wrong dose or miss a dose, immediately contact your doctor as this may put you at risk of bleeding or clotting.

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.

Watch our video, in which Libby talks about her routine for taking warfarin. Libby tells us about her system for remembering to take warfarin at the same time every day, and how she remembers to take her other medicines.


What if I take an extra dose of warfarin?

Seek medical advice immediately or contact the Poisons Information Centre (call 13 11 26; 24 hours a day, 7 days a week).

Go to the emergency department at your nearest hospital if you are concerned or you notice signs of bleeding, for example blood in your urine or stools, or abnormal bruising.

Keep the telephone numbers for your doctor, the Poisons Information Centre and your nearest hospital handy in case of an emergency.

What do I do if I forget a dose?

It’s important to take your warfarin every day, at the same time. However if you forget to take it, only take the missed dose if you remember within 4 hours of the time you usually take it.

Don’t take the missed dose if you remember more than 4 hours after the time you normally take it. Take your next dose the next morning or evening at the usual time.

Don’t take a double dose at any time.

For more information