Anticoagulants, warfarin - Side effects 

Side effects of warfarin 

Reporting side effects

The Yellow Card Scheme allows you to report suspected side effects from any medicine that you are taking. It is run by a medicines safety watchdog called the Medicines and Healthcare products Regulatory Agency (MHRA). See the Yellow Card Scheme website for more information.

It is important to check for bleeding (haemorrhages) when taking warfarin as anticoagulants can cause excessive bleeding.

You must seek medical attention and have an urgent blood test if you experience any of the following:

  • passing blood in your urine or faeces
  • passing black faeces
  • severe bruising
  • long nosebleeds (lasting longer than 10 minutes)
  • bleeding gums
  • blood in your vomit or coughing up blood
  • unusual headaches
  • (in women) heavy or increased bleeding during your period, or any other bleeding from the vagina

You must seek immediate medical attention if you:

  • are involved in a major accident
  • experience a significant blow to the head
  • are unable to stop any bleeding

Less common side effects

Less common side effects of warfarin include:

See your GP immediately if you experience jaundice (yellowing of the skin and whites of the eyes) or any persistent side effects whilst taking warfarin.

Last reviewed: 22/03/2012

Next review due: 22/03/2014

The Yellow Card Scheme

The MHRA has produced a video that explains how the Yellow Card Scheme can be used to report the side effects of medication