Warfarin - what to do if you miss a dose

Published in Medicinewise Living

Date published: About this date

Take your warfarin at the same time every day. (Yuri Arcurs / Shutterstock.com)

If you, or someone you care for, are taking warfarin, you’ll know how important it is to take it exactly as prescribed. You’ll also be familiar with the ups and downs of INR monitoring — the regular test you have that indicates how fast your blood clots.

Many factors can affect your INR — one of the simplest ways to help keep your INR stable is to take warfarin at the same time every day. Read on, to find out more about living safely with warfarin and what to do if you miss a daily dose.

When should I take warfarin?

Warfarin is usually taken once a day, at the same time each day, usually in the evening. To make sure you never miss a dose of warfarin, you could set an alarm or a reminder on your mobile phone, or use another trigger such as the evening news on TV.

How much warfarin do I take?

A health professional will always tell you how much warfarin to take. Your dose may be different on different days.

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 to help you tell the difference between them. The colour of the different strength tablets also differs between brands. Make sure you always take your usual brand.

Ensure you’re taking the right dose, 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.

How should I take warfarin?

Take your recommended daily dose exactly as directed by a health professional. You can take warfarin with or without food. Tablets should be swallowed whole, with a glass of water (don’t crush or chew them).

What to do if you forget to take 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.
  • If you miss a dose altogether, don’t take a double dose at any time.
  • If you have missed a dose and you are unsure what to do, ask your doctor or pharmacist.
  • Keep a note of any doses that you miss and tell your health professional.

What if I accidentally take an extra dose of warfarin?

Seek medical advice immediately or contact the Poisons Information Centre (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.

Tips for being medicinewise with warfarin

Here are 5 medicinewise steps to make sure you take warfarin safely and effectively:

  • Take warfarin at the same time every day — set a reminder if necessary.
  • Always take the recommended daily dose. Keep a record of your daily dose.
  • If you miss a dose, and are unsure what to do, ask your doctor or pharmacist for advice.
  • Never take a double dose. Seek medical advice immediately if this happens.
  • Always talk to your doctor or pharmacist before starting any new medicine including vitamins, herbal and mineral supplements.

Find out more about warfarin

  1. Living with warfarin. Government of Western Australia Department of Health. http://www.health.wa.gov.au/docreg/Education/Population/Health_Problems/HP8948_warfarin_B.pdf (last accessed 4 February 2013).
  2. Important information for patients: Warfarin. Aspen Australia.
  3. Marevan Consumer Medicine Information Leaflet available from: http://www.nps.org.au/medicines/heart-blood-and-blood-vessels/anti-clotting-medicines/warfarin/for-individuals/brands/marevan-tablets
  4. Coumadin Consumer Medicine Information Leaflet available from: www.nps.org.au/medicines/heart-blood-and-blood-vessels/anti-clotting-medicines/warfarin/for-individuals/brands/coumadin-tablets