Caring for someone taking warfarin

Published in Medicinewise Living

Date published: About this date

Help someone you care for take warfarin safely by knowing as much as you can about it. Image: Rido /

Caring for someone living with warfarin can be demanding, but you can help them take warfarin safely by knowing as much as you can about it. Here are some facts you need to know and where you can find more information and support.  

What is warfarin, what does it do?

Warfarin is an anti-clotting medicine (anticoagulant) used to prevent or treat harmful blood clots that can cause a stroke or blockage in a vein or lung. It has been used for more than 60 years and is taken by thousands of Australians every day.

Many people believe warfarin works by thinning the blood, but it actually slows down the process of blood clotting to prevent unwanted blood clots forming in blood vessels.

Why do people need warfarin?

Warfarin is prescribed for people who have:

  • an irregular heart beat (atrial fibrillation), which increases the risk of stroke
  • had a blood clot in their legs (deep vein thrombosis or DVT) or lungs (pulmonary embolism or PE).

Others may need to take warfarin to treat a blood-clotting problem, or if they’ve had a mechanical heart valve inserted.

What is an INR test?

The INR (International Normalised Ratio) test measures the time it takes for blood to clot. Anyone taking warfarin will need to have this blood test regularly to monitor how well warfarin is working.

The aim is to find a safe balance (INR of 2–3) so the blood doesn’t clot too fast or too slowly to cause bleeding. A doctor will use the INR result to decide if a warfarin dose needs changing.

What can affect INR?

Changes to diet, alcohol intake, illness, other medicines and travel can all affect INR.

People taking warfarin should avoid major changes to their diet — consistency is the key. Limit alcohol intake to no more than 2 standard drinks per day.

Can people taking warfarin eat green leafy vegetables?

People taking warfarin can eat green leafy vegetables. But it’s important that they eat the same amount of these foods each week to help keep their INR stable. This is because green leafy vegetables (e.g. spinach, broccoli, Brussels sprouts) are rich in vitamin K, which can affect INR.

Don’t avoid foods rich in vitamin K completely. Studies show that eating regular, consistent amounts of foods rich in vitamin K is better for maintaining a stable INR, than not eating them at all, or eating varying amounts.

Who do I need to tell?

Tell all health professionals involved in the person’s care including pharmacists, dentists, surgeons and nurses. It’s important they know about their warfarin before starting or changing any medicines, before any major surgery, or before giving an injection.

Health professionals also need to know if the person you’re caring for has any other health conditions, including liver or kidney problems, high blood pressure, or an ulcer anywhere in the digestive tract.

Warfarin can interact with many prescription, over-the-counter and complementary medicines (including vitamins) and this can affect blood clotting.

How should warfarin be taken?

Warfarin is taken once a day, at the same time each day, usually in the evening. This will help keep the INR stable.

To ensure you give a dose, you could set an alarm or a reminder on your mobile phone, or use another trigger such as the evening news on TV.

Are brands of warfarin interchangeable?

Warfarin brands are not interchangeable so it’s important to always stick with the same brand (Marevan or Coumadin).

Also, make sure you check the tablet strength on the medicine label or packaging. Warfarin comes in different tablet strengths and a doctor may prescribe more than one to make up the dose. Different strength tablets have different colours to help you tell the difference between them. Tablet colours also differ between brands.

What happens if I forget a dose?

It’s important that warfarin is taken every day, at the same time. However, if you forget, only give the missed dose if you remember within 4 hours of the time the person you care for normally takes it.

Don’t give the missed dose if you remember more than 4 hours after the time the person you care for normally takes it. Give the next dose the next morning or evening at the usual time.

If you miss a dose altogether, don’t give a double dose at any time. Keep a note of any missed doses.

If you are unsure what to do, ask a doctor or pharmacist.

What are the side effects of warfarin?

The most serious side effect of warfarin, or any anticoagulant, is bleeding. To help reduce the risk of bleeding, the person you’re caring for should:

  • take warfarin exactly as directed at the same time every day
  • avoid activities that could cause bleeding from an injury or fall.

How do I spot signs of bleeding?

Some types of bleeding may not be obvious and can be more serious than others. So it’s important to ask a health professional:

  • what signs and symptoms to look out for
  • when you should contact your doctor
  • when you need to go to a hospital emergency department.

Report any accidents and injuries to a health professional — including falls and bruising — even if you don’t notice any bleeding.

What precautions can I take to prevent injuries?

If someone in your care can’t avoid activities that may cause an injury or fall, take other precautions to limit their risk (for example, protective clothing).

You, or the person you’re caring for, can also reduce falls and injuries in the home by:

  • taking extra care with sharp objects like knives
  • wearing gloves when gardening
  • securing loose floor rugs, and electrical or phone cords
  • using a non-slip mat for the bath or shower
  • using an electric shaver
  • using a soft bristled or electric tooth brush.

What about travelling with warfarin?

A visit to their doctor well ahead of travel is essential in case an INR test is needed beforehand. They may also need to have their INR checked while travelling, especially if:

  • it’s not in the target range (INR 2–3) before they leave
  • they’ve just started taking warfarin
  • they’re taking or starting another medicine known to affect INR or warfarin.

Ask when their daily dose of warfarin should be taken in different time zones and ensure enough warfarin is packed for the whole time they’re away.

Tips for carers

  1. Ask the doctor or person in your care why they’re taking warfarin if you’re unsure.
  2. Anyone taking warfarin needs to have their INR tested as often as recommended by a health professional. Never skip tests.
  3. Keep a record of their INR result and daily dose. Some people may need to take a different dose everyday or every other day.
  4. Ask a doctor or pharmacist if you’re unsure what dose or tablet strength you need to give.
  5. Always tell all health professionals that someone in your care is taking warfarin.
  6. If you’ve missed a dose or mistakenly given a double dose, and you’re unsure what to do, ask a doctor or pharmacist.
  7. Keep a note of any missed or double doses and tell their doctor.
  8. Let their doctor know if the person you’re caring for has made any major changes to their lifestyle, including diet or alcohol intake.
  9. Seek medical advice if the person you’re caring for feels unwell, even if you don’t think it is related to the warfarin.
  10. Look after yourself too.

Further information and support for carers

Caring for others can be demanding and stressful, and sometimes lonely. Read more about how to look after yourself if you’re a carer, including taking breaks and where you can seek help.

Learn more about living with warfarin, the how, what and why of warfarin and what to do if you miss a dose.

You can also call the NPS Medicines Line on 1300 MEDICINE (1300 633 424) for information about medicines from a health professional.