DOAC monitoring

Although the direct oral anticoagulants (DOAC) are attractive from many view points and their predictable pharmacokinetic dose-response curve allows fixed dosing, evaluation of anticoagulant activity might be indicated in the following circumstances:

  • in those patients are the extremes of weight, i.e. <50kg and those patients weighing >120kg
  • in cases of overdose or toxicity
  • in patients with significant renal and liver dysfunction
  • when patients are prescribed concurrent drugs, known to interact with DOAC
  • to confirm oral absorption
  • to confirm clearance of the DOAC prior to an invasive procedure
  • to assess adherence to DOAC

The Kings Anticoagulation Reference centre routinely quantitatively assays the DOAC and provides interpretive advice, so that healthcare professionals are able to individualise anticoagulant therapy for their patients.

If you wish to utilise this service, please review the ‘recommended times to draw DOAC samples’ table below and complete the appropriate request form below (under sampling handling).

It is important that all information in the relevant form is complete.

Recommended times to draw DOAC samples, in order to be informative:

Scenario Timing of drawing sample
Extremes of weight Trough activity
Overdose or suspected over-anticoagulation Anytime (time since last dose(s) should be recorded on request form)
Renal or liver dysfunction Trough activity
Patient on concomitant interacting drugs Trough activity
To confirm oral absorption Peak activity
To assess adherence Anytime (time since patients claimed last dose should be recorded on the request form)

Trough activity refers to sample being drawn, prior to next dose. Peak activity refers to sample being drawn 1-3 hours post dose for dabigatran and 2-3 hours for rivaroxaban, apixaban and edoxaban.

Sample handling:

Rivaroxaban and Dabigatran samples (local):

Please download the following form and complete all information, and ask patient to attend the phlebotomy department at King’s College Hospital. Please refer to the ideal sample time table above, and encourage patient to attend at the relevant time for the sample, so that an informative result is obtained.

Rivaroxaban and Dabigatran samples (out of area):

Please download the following form and complete all information. Specific instructions on how the sample should be handled and shipped are documented on this form. Please refer to the ideal sample time table above when drawing the relevant sample(s).

Send the sample and the completed form to:


Blood Sciences Laboratory- Coagulation Lab
King’s Thrombosis Centre
King’s College Hospital
Denmark Hill

Reporting of results:

Results from samples received, will be sent back to the requesting professional by email.

Interpreting results:

If you wish to discuss a particular patient before deciding on whether to get the drug assayed or wish to discuss a result, please email Jig Patel at in the first instance.

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