Warfarin Counselling – OSCE guide

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This guide provides an overview of how to counsel a patient about warfarin therapy in an OSCE setting.

Before beginning

Begin by reviewing the patient’s medical background to establish the current indication for warfarin and the patient’s target INR range.

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Opening the consultation

Wash your hands and don PPE if appropriate.

Introduce yourself to the patient including yourΒ nameΒ andΒ role.

Confirm the patient’sΒ nameΒ andΒ date of birth.

Explain the reason for the consultation

Ideas, concerns and expectations


Explore what the patient currently understands about warfarin and why they are being prescribed it:

  • “Have you heard of warfarin?”
  • “What do you already know about warfarin?”
  • “Do you know why people take warfarin?”


Ask if the patient has any concerns about warfarin:

  • “Is there anything that worries you about taking warfarin?”


Explore what the patient is hoping to get out of the consultation:

  • “What were you hoping we’d discuss today?”

How warfarin works

Using patient-friendly language, explain how warfarin works.

“Warfarin is a type of medicine known as an anticoagulant. It helps to thin the blood, making it less likely that a dangerous blood clot could form.”

“Warfarin can be used to treat people who have a previous blood clot in the leg or lungs. It can also be used to prevent future blood clots in people who are at high risk of having them in the future, such as people with an irregular heartbeat or an artificial heart valve.”

“The action of warfarin can be rapidly reversed with an antidote in situations where we need to reduce the risk of bleeding.”


Explain the role of INR in monitoring the effect of warfarin.

“The INR is a measure of how long it takes blood to clot. In healthy people an INR of 1 is normal. Since you are at a higher risk for blood clots we want your blood to be thinner than normal and therefore take longer to clot. As a result, the target range for your INR would be between 2-3, meaning it takes two to three times as long for your blood to clot compared to someone not taking warfarin.”

β€œIn order to ensure that we keep your blood within the necessary range we will need to monitor your INR level every so often; this is done through a blood test. The blood tests will initially be frequent (every 3-4 days until two consecutive readings are within range), and then after this, you will be tested twice weekly for 1-2 weeks (again until two consecutive readings within range). Thereafter, testing can increase to longer periods (e.g. every 12 weeks). Your dose of warfarin will be adjusted based on the INR results with the aim of keeping it within the target range.”

How to take warfarin

Key points to communicate when discussing warfarin use:

  • “Warfarin should be taken at the same time each day to keep the levels of warfarin steady.”
  • “Tablets have different colours depending on their strength (e.g. 0.5mg white; 1mg brown; 3mg blue; 5mg pink).”
  • “If you forget to take a dose you should take it as soon as you remember, but if you don’t remember till the following day you should skip the missed dose. You should never take two doses together to make up for a missed dose and you should inform your doctor or warfarin clinic about any missed doses at your next appointment.”
  • “Whenever you are going to purchase or be prescribed a new medication you should let the doctor or pharmacist know that you take warfarin so they can avoid prescribing medications which alter your warfarin level.”
  • “When you start taking a new medication you should let your doctor or anticoagulant clinic know so that they can consider if your warfarin levels need monitoring more frequently.”
  • “You should continue to take your warfarin tablets regularly until you have been told to stop.”
  • “Warfarin is not safe to be used during pregnancy and therefore you should have an effective contraceptive method in place before you start taking warfarin.”

Bleeding whilst on warfarin

The main side effect of warfarin involves bleeding more easily than normal (e.g. epistaxis, bleeding gums, heavier periods, bruising). These side effects most commonly occur in the first few weeks of treatment or when the patient is unwell. It is important to discuss the different types of bleeding the patient may experience and inform them what to do in these situations.

Less serious bleeding

“It is normal to bleed more easily when taking warfarin as the medication works by thinning the blood. Common types of bleeding include:

  • periods that are heavier and last longer than normal
  • bleeding for a little longer than usual if you cut yourself
  • occasional nosebleeds (that last for less than 10 minutes)
  • bleeding from your gums when you brush your teeth
  • bruises that come up more easily and take longer to fade than usual

This type of bleeding is not dangerous and should stop by itself. If it happens, keep taking the warfarin, but tell your doctor if the bleeding bothers you or does not stop.”

Serious bleeding

“Occasionally, you can have serious bleeding from taking warfarin. This can be dangerous and needs urgent medical attention.”

“Stop taking warfarin and call your doctor or anticoagulant clinic, or go to A&E if you experience:

  • red pee or black poo
  • large bruises or bruises that happen for no reason
  • nosebleeds that last longer than 10 minutes
  • blood in your vomit or you’re coughing up blood
  • severe headaches, fits (seizures), changes to your eyesight, numbness or tingling in your arms or legs, or feel very tired, weak or sick – these can be signs of bleeding in your brain
  • any bleeding from a cut or injury that will not stop or slow down”

Other side effects of warfarin

Common side effects

Common side effects (other than bleeding) of warfarin include:

  • a mild rash
  • hair loss

These side effects are typically mild and the patient should be advised to contact their doctor or pharmacist if they become bothersome.

Serious side effects

Serious side effects of warfarin can include:

  • jaundice
  • skin necrosis

As a result, patients should be advised to seek urgent medical review if they develop:

  • yellowing of the skin
  • painful swollen areas of skin

Lifestyle advice


Drastic changes in diet, especially an increase in consumption of foods high in vitamin K (such as broccoli, kale, or spinach) can potentially affect control of anticoagulation. If the patient ever wishes to significantly change their diet, they should inform the anticoagulant clinic so necessary dose adjustments and monitoring requirements can be fulfilled. Cranberry juice is also known to interact with warfarin and enhance its anticoagulant effect and therefore it should be avoided.


Patients should limit their alcohol intake to a maximum of one or two drinks a day and never binge drink. If there are major changes in alcohol consumption (e.g. the patient stops drinking, or starts drinking more) the INR can be affected.


Patients should be advised to take extra care when carrying out routine tasks such as brushing teeth or shaving; a soft toothbrush or an electric razor can help. Patients should also be advised to inform their dentist that they take warfarin when booking an appointment as this may have implications for dental procedures.

Yellow booklets and alert card

At the start of treatment, all patients should be provided with two yellow anticoagulant booklets, an INR monitoring booklet and a patient information booklet. Patients should also be provided with an anticoagulant alert card.

Patients should be advised to always carry the anticoagulant alert card with them in case of an emergency and always take the yellow INR monitoring book with them to each appointment at the anticoagulant clinic and if possible to other appointments (e.g. GP, pharmacy reviews, dental appointments etc).

The patient information book is a useful resource since it provides the patient with a point of reference and reinforces what has been covered in this guide.

Closing the consultation

SummariseΒ theΒ keyΒ pointsΒ back to the patient.

Ask the patient if they have anyΒ questionsΒ orΒ concernsΒ that have not been addressed.

If you feel that the patient would benefit from a recap session, arrange a follow-up appointment (face-to-face or telephone) and also direct the patient to the yellow anticoagulant information booklet for further reading.

Thank the patient for their time.

Dispose of PPE appropriately and wash your hands.


  1. NHS.uk. Warfarin. Available from: [LINK].
  2. BNF. Warfarin. Available from: [LINK].

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