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What does it do?

Warfarin is used to prevent clots forming in your blood. It reduces your risk of having a stroke and stops new clots forming in your legs or lungs.

How should you take it?

Take warfarin regularly as directed. Take it with a glass of water at the same time each day. Follow your health professional’s instructions carefully to make sure you take the right dose.
Warfarin comes in two brands in NZ (Marevan® and Coumadin®). Check which brand you have and stick to it.
Warfarin comes in different strengths, with different colours. Most people take the Marevan® brand shown in the picture below. If your tablets look different than usual, check with your pharmacist.

Warfarin sheet image

What if you forget a dose?

Take the missed dose if you remember on the same day. If not, skip the dose and carry on as normal. Do not take two doses on the same day. Record the missed doses in your anticoagulant booklet and tell your doctor on your next visit.

Can you take other medicines?

Some medicines available without a prescription may react with warfarin including:

  • anti-inflammatories, such as diclofenac (e.g. Voltaren®), ibuprofen (e.g. Nurofen®), or aspirin (e.g. Disprin®, in doses used for pain relief). These can also be found in some cold and flu medicines (e.g. Nurofen Cold and Flu®).
  • low-dose aspirin (e.g. Cartia®)
  • orlistat (Xenical®)
  • fluconazole (e.g. Diflucan®) or miconazole (e.g. Daktarin Oral Gel®)
  • omeprazole (e.g. Losec®)

Tell your pharmacist or doctor about all medicines or treatments that you may be taking, including vitamins (e.g. vitamin K, vitamin E), herbal products (e.g. St John's wort) or recreational drugs.

What side effects might you notice?

Side EffectsRecommended action

Easy/unusual bruising or bleeding

Coughing or vomiting of blood, vomit that looks like coffee grounds, nose bleeds

Red or dark brown urine, red or black bowel motions

Chest pain, trouble breathing

Headache, dizziness, changes in vision or speech

Skin rash, skin discolouration (blue or purple)

Tell your doctor immediately

Yellow skin or eyes

Tell your doctor

Hair loss or thinning

Stomach upset

Tell your doctor if troublesome

If you notice any other effects, discuss them with your doctor or pharmacist.

Other information:

  • Tell your doctor if you have heart, liver, stomach or bleeding problems.
  • Tell your doctor if you are pregnant, planning to become pregnant, or breastfeeding.
  • It is important to tell anyone who gives you medical or dental treatment that you are taking warfarin.
  • Tell your doctor if you become unwell or change your diet - your warfarin dose may need to be changed.
  • You will need a regular blood test (INR) while taking warfarin to make sure that you are taking the correct dose.
  • Alcohol increases the risk of severe bleeding while on warfarin. Alcohol intake should be limited – discuss this with your doctor or pharmacist.

This leaflet contains important, but not all, information about this medicine.

Prepared by the PILs Committee at Christchurch Hospital, Canterbury District Health Board, New Zealand. November 2017

For more general information about this sheet and its contents, see: What does a My Medicines sheet cover?

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About My Medicines

My Medicines Patient Information Leaflets (PILs) contain important, but not all, information about the medicines they describe.

For more information about the sheets, see: What does a My Medicines sheet cover?

My Medicines is developed by a team at the Canterbury District Health Board. Our team is made up of doctors, pharmacists, and a non-medical person to help us keep to plain language. We also discuss our information with specialist health professionals or groups when needed