Prothrombin is a protein produced in the liver. It plays an important role
in blood clotting: Reductions in prothrombin will lead to decreased clotting
ability of the blood.
The PT (ProTime, Prothrombin Time) measures impairment of the clotting
effects of prothrombin, fibrinogen, and coagulation Factors II, VII, IX, and
Any process that interferes with the production of prothrombin (liver
disease, Vitamin K deficiency, Coumarin-based anticoagulants) may impair the
ability of blood to clot, and can be measured by a prolongation of the
Prothrombin Time (PT).
Patients being treated with oral anticoagulants are monitored with PT, to
make sure they are within the therapeutic range.
- If they aren't receiving enough anticoagulant, the treatment may be
- If they receive too much anticoagulant, they may lose too much ability
to clot and sustain injury as a consequence.
Prolonged PT is associated with:
- Liver disease
- Vitamin K deficiency
- Anticoagulant (Coumarin, Coumadin) therapy
- 2-2.5 times the normal
- Not more than 30 seconds
||10-14 seconds (100%)
Therapeutic Range on oral anticoagulants
||2-2.5 times normal, but not
*These are general values taken from a variety of
sources. The actual normal values may vary from lab to lab and from one
type of testing protocol to another.