Pathology Handbook

Warfarin level


Serum warfarin, plasma warfarin

Clinical Indications

Suspected non-compliance with oral anticoagulant therapy, suspected warfarin resistance, suspected ingestion of super warfarin (specific) rat poisons)

DO NOT request this test for routine warfarin monitoring

Test includes Warfarin and, if ingestion of rat poison is suspected, super-warfarin

Request Form 

Request via ICE


Mon - Thu 9AM to 4PM
Not available on Fridays due to sample stability issues.

Specific Criteria

Samples should be taken with minimal stasis and kept in the dark

Patient Preparation

To exclude the influence of recent dietary intake it is preferable that blood samples should be collected after an overnight fast

Turnaround Time

10 working days (sent externally)


Fresh citrated Blood (within 2 hours of collection)


4.5 ml blue citrated blood


4.5 ml blue citrated bottles

Vacutainer blue top


Samples should be taken with minimal stasis and taken to the laboratory immediately

Causes for Rejection

Underfilled, clotted or haemolysed samples

Reference Range

Theraputic range= 0.7 - 2.3mg/L