Side effects of warfarin

Bleeding is the main side effect associated with warfarin, as it slows down the blood's normal clotting ability.

You're at greatest risk of bleeding in the first few weeks of starting treatment with warfarin and when you're unwell.

You should therefore seek medical attention if you:

  • pass blood in your urine or faeces
  • pass black faeces
  • have severe bruising
  • have long nosebleeds lasting more than 10 minutes
  • have bleeding gums
  • cough up blood or have blood in your vomit
  • experience unusual headaches
  • have heavy or increased bleeding during your period , or any other bleeding from your vagina(in women)

Take extra care to avoid cutting yourself while taking anticoagulant medication because of the risk of excessive bleeding.

For example, you should:

  • take care when shaving and brushing your teeth
  • wear protective clothing when gardening, sewing or playing contact sports
  • use insect repellent to avoid insect bites or stings

Seek urgent medical attention if you're taking warfarin and you:

  • have a fall or accident
  • experience a significant blow to your head
  • are unable to stop any bleeding
  • have signs of bleeding, such as bruising

Skin rashes and hair loss are also common side effects of warfarin.

Contact your GP or the healthcare specialist responsible for your care if you experience any persistent side effects while taking warfarin.

Content supplied by the NHS Website

Medically Reviewed by a doctor on 21 Dec 2018