Treatments and tests

Warfarin and risk of bleeding

Bleeding is the most common side effect of taking warfarin.

Keeping your International Normalised Ratio (INR) within the target range reduces your risk of bleeding. Your INR is a measure of how long your blood takes to clot.

Other things you need to do to reduce the risk of harm from bleeding include:

  • knowing what to do if bleeding starts
  • telling your doctor or dentist that you take warfarin well before any procedure or surgery
  • avoiding activities and sport that might cause you serious injuries.

Signs and symptoms

Contact your doctor right away if you have any signs or symptoms of unusual bleeding. This can include:

  • bleeding that takes a long time to stop (this includes nose bleeds, bleeding from your gums, bleeding from cuts and scrapes and menstrual periods)
  • severe unexplained bruising, or bruising that gets bigger
  • red or dark coloured urine
  • red or black bowel motions
  • coughing blood
  • dark or blood-stained vomit
  • severe headache or dizziness
  • new pain, swelling or discomfort.

What will my doctor do?

Depending on your symptoms your doctor will do 1 or more of the following:

  • order a blood test
  • reduce your doses of warfarin
  • stop you from taking warfarin for a few days
  • give you a vitamin K injection to slow down the bleeding.

Medical and dental procedures

Bleeding from medical or dental procedures may be increased with warfarin. For some procedures you will need to stop your warfarin temporarily.

Tell your doctor or dentist that you take warfarin well before any planned procedure (including operations in hospital, minor procedures at the doctor’s surgery and some dental work).

Your warfarin therapy will be considered in the planning of your operation or procedure. Do not stop taking your warfarin unless told by your doctor.

Avoiding injuries

Contact your doctor for advice before starting any activity that may cause injury.

When taking warfarin you can perform all your normal daily activities but you are at risk of excess bleeding if you are injured.

What can I do?

It is best to avoid activities that might cause injuries associated with bleeding.

These include contact sports such as football, rugby, boxing) as well as other activities where there is a risk of severe knocks, bumps or bruises.

If you are unsure which sports and activities are safe for you, ask your doctor.

You should also be aware of the risk of falls and take steps to minimise your risk. Falls may lead to significant head injury and increased risk of bleeding into or around your brain.

Remember, you might not see any visible signs of bleeding from an internal injury. Tell your doctor about any:

  • falls
  • blows to the head or body
  • other major injuries.

You may also consider using an electric razor instead of a blade.

Remember to clean and treat minor cuts and scrapes immediately. Tell your doctor about any bleeding that is hard to stop or if pain and swelling develops.

For emergencies

If you have an accident or become very ill, ambulance and hospital staff need to know that you take warfarin.

It’s important that you carry identification with you that mentions you take warfarin. This might be a Warfarin Treatment Card or a Medic Alert. It is also a good idea to carry an up-to-date-list of all your medicines.

Medic alert

Patients on long term warfarin should consider joining MedicAlert (external site). Your doctor can help you do this.

Joining MedicAlert involves providing personal details and medical history about your warfarin therapy. This vital patient information can then be accessed by medical and emergency workers during emergencies.

You are provided with a personalised engraved bracelet or pendant and a wallet-card that identifies that you take warfarin.

Where to get help

  • See your doctor.
  • Visit a GP after hours.
  • Ring healthdirect Australia on 1800 022 222.

Medic Alert

Medicines information line

  • Free independent advice from medical specialists
  • Phone 1300 633 424 (local call rates from land line only)
  • Read more about the Medicines Line (external site)

Poisons information line

  • Immediate specialist advice for overdoses or poisoning
  • Phone 13 11 26 (local call rates from land line only)

Adverse Medicines Events Line

National Prescribing Service (NPS) MedicineWise


  • Bleeding is the most common side effect of taking warfarin.
  • Avoid activities that may cause injuries that bleed.
  • You may wish to consider carrying a Warfarin Treatment Card or MedicAlert for emergency situations.


Western Australian Therapeutic Advisory Group | The WA Medication Safety Group

This publication is provided for education and information purposes only. It is not a substitute for professional medical care. Information about a therapy, service, product or treatment does not imply endorsement and is not intended to replace advice from your healthcare professional. Readers should note that over time currency and completeness of the information may change. All users should seek advice from a qualified healthcare professional for a diagnosis and answers to their medical questions.

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