Warfarin or another Vitamin K antagonist

Refer to Section 6 of the full guidance.

Key recommendation

For a patient who is taking warfarin or another vitamin K antagonist, with an INR below 4, treat without interrupting their anticoagulant medication.
(Strong recommendation; low certainty evidence) [unchanged 2022]

This recommendation is based on the available evidence and extensive clinical experience. Low certainty evidence from several systematic reviews suggests that although the bleeding risk for dental procedures is likely to be higher in patients on VKA therapy than in non-anticoagulated patients, there might not be any significant difference for patients continuing versus interrupting their VKA. Overall, the bleeding risk is low and in the vast majority of cases, bleeding events can be controlled with local haemostatic measures.

This is considered to be a strong recommendation because of emphasis placed on the potential risk of a serious thromboembolic event if warfarin treatment is interrupted. 

For dental treatment that is likely to cause bleeding, with either a low or higher risk of bleeding complications (see Bleeding risks for dental procedures):

  • Ensure that the patient’s INR has been checked, ideally no more than 24 hours before the procedure. If the patient has a stable INR, checking the INR no more than 72 hours before is acceptable.
    • Based on the BNF’s definition, a stable patient would be one who does not require weekly monitoring and who has not had any INR measurements above 4 in the last two months
    • If there is reason to believe that a test result obtained up to 72 hours before dental treatment may not reflect the current level, then the patient's INR should be tested again no more than 24 hours before the dental procedure
  • If the patient’s INR is 4 or above, inform the patient’s anticoagulation service or general medical practitioner or and delay invasive dental treatmenta until the patient’s INR has been reduced to less than 4. For urgent treatment, refer the patient to secondary dental care.
  • If the patient’s INR is below 4, treat according to the general advice for managing bleeding risk, without interrupting their anticoagulant.

In addition:

  • Consider limiting the initial treatment area (e.g. perform a single extraction or limit root surface debridement to 3 teeth, then assess bleeding before continuing).
  • For procedures with a higher risk of post-operative bleeding complications (see Bleeding risks for dental procedures), consider carrying out the treatments in a staged manner, where possible, over separate visits.
  • Use local haemostatic measures to achieve haemostasis. Strongly consider suturing and packing, taking into account all relevant patient factors (see Haemostatic measures).

a If the patient is prescribed an antibiotic for the dental condition, be aware that this may affect their INR level (see Interactions with drugs prescribed by dentists).

Although the use of warfarin is well established, managing its therapeutic anticoagulation activity can be complicated.

Warfarin activity has to be monitored frequently due to:

  • substantial drug and dietary interactions
  • variation in patients’ responses to the drug
  • the drug's narrow therapeutic range

This is achieved using the INR (International Normalised Ratio) test, which measures the time taken for a clot to form in a blood sample, relative to a standard.

  • An INR value of 1 indicates a level of coagulation equivalent to that of an average patient not taking warfarin
  • Values greater than 1 indicate a longer clotting time and thus a longer bleeding time

The INR test is also used for patients taking the less commonly used VKAs, acenocoumarol and phenindione.

Target INR levels differ depending on the indication for which the drug is prescribed and can range from 2.5-3.5 ± 0.5.

A patient’s warfarin therapy will be adjusted by their medical practitioner or anticoagulation service (or by the patient if self-monitoring) as necessary to achieve the target INR level appropriate for their medical condition.

Patients taking warfarin will have a record of their INR test results, which they should present when attending for dental treatment.