Department of Haematology


  • Manipulation of the prothrombin time (PT) to International Normalised ratio (INR) provides a standardised measure of anticoagulant therapy with Vitamin K antagonists, but is not valid for patients receiving other anticoagulants, screening for coagulation defects, or as a marker for the severity of liver dysfunction. If the request does not fulfill these criteria, the INR will not be performed.
  • Samples that are under filled, overfilled or haemolysed give erroneous results and therefore will not be tested.
  • Test performed at CGH and GRH

See also:

Sample Requirements

2ml, 3ml or 3.5ml Trisodium Citrate sample

3ml Trisodium citrate

Turnaround Times

  • Urgent, clinical emergency: 30 minutes
  • Other urgent sample: 60 minutes
  • Routine: 2 hours

Reference Ranges

For therapeutic ranges, please see BCSH Guidelines.

GP telephone ranges:

INRs of <1.5 or >5.0