Indicator Explainer
Prothrombin Time
A measurement of the clotting time of plasma recalcified in the presence of excess tissue thromboplastin; it is a measure of the extrinsic pathway of coagulation. It is used to determine the clotting tendency of blood, in the measure of warfarin dosage, liver damage and vitamin K status. Factors measured are fibrinogen, prothrombin, and factors V, VII, and X.
This page explains what the indicator is and how results are interpreted in general terms. Reference ranges depend on the laboratory, the method, and your own situation — no single “normal value” applies to everyone. This page is health information, not a diagnosis. For symptoms, treatment, or urgent concerns, contact a healthcare professional.
When it is tested
Source: National Cancer Institute, NCI Thesaurus 26.09d, C62656. NCI definition, reproduced without modification under CC BY 4.0. Source identity and definition checked automatically on 2026-10-19. No individual clinical interpretation or human reviewer is asserted.
Reading results
Reference intervals and interpretation depend on the laboratory, specimen, method and clinical context. This source definition is educational information; it does not establish a diagnosis, product approval or suitability for an individual.