Page last updated April 2018

This is a FREE resource designed to support the medical profession in their care of women made possible by over 750 expert clinicians who are generously providing their contributions without any remuneration and by the publishers who have paid personally for the creation of this site in the memory of their daughter, Abigail.

Current Authors

PTT (Partial Thromboplastin Time)

PTT detects nearly all abnormalities in clotting, due to deficiencies in clotting factors or circulating anticoagulants.

It is frequently used to monitor heparin therapy.

A modification of the test, "Activated PTT," or APTT, is basically the same as PTT, but is slightly more sensitive.

Prolonged PTT is associated with:

  • Liver disease
  • Vitamin K deficiency
  • Anticoagulant (Coumarin, Coumadin, Heparin) therapy
  • DIC
  • Hemophilia

Therapeutic Range (Heparin Therapy)

  • 2-2.5 times the normal

Normal Values*

PTT 30-45 seconds 
APTT 16-25 seconds
Therapeutic Range on oral anticoagulants 2-2.5 times normal

*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.