Thrombin time measurement is the time it takes for a fibrin clot to form after reagent addition, results are reported in seconds. If the clotting time of a sample is prolonged beyond the reference range, the level or activity of fibrinogen is low or thrombin inhibitors may be present.

Thrombin time is used :
- to qualitatively detect fibrinogen abnormalities.
- to assess the effectiveness of fibrinolytic treatment.