PT, INR (Prothrombin Time)
Fasting Required: No

Specimen: Blood

Lab: Quest Diagnostics

Results: 1-2 business days
Note: Result turnaround times are an estimate and are not guaranteed. Our reference lab may need additional time due to weather, holidays, confirmation/repeat testing, or equipment maintenance.

Limitations: Expected impact by therapeutic levels (potential interference depends upon drug concentration): Warfarin: prolonged; Heparin (UFH or LMWH): little to no effect (reagent contains a heparin neutralizer); Dabigatran or Argatroban (Thrombin Inhibitors): normal to prolonged; Rivaroxaban or Apixaban (Factor Xa Inhibitors): prolonged.

Description: The Prothrombin time (PT) test is most often used to check how well anti-coagulant or “blood-thinning” drugs are working. Anti-coagulant drugs help prevent the formation of blood clots. This is particularly important in people who have had a heart attack or other problems with their veins. The drug’s effectiveness can be determined by how much it prolongs the prothrombin-to-thrombin conversion time.

Alternative Name(s): PT