Prothrombin Time · high result
What does a high Prothrombin Time mean?
Short answer
A prolonged prothrombin time means the extrinsic clotting pathway is slow. On warfarin it is the intended effect (tracked as INR, usually 2–3). Off anticoagulants, it points to vitamin K deficiency, liver disease (the liver makes the clotting factors), a factor VII deficiency, disseminated intravascular coagulation in severe illness, or a lab artifact from an under-filled tube. It is read with the aPTT and platelet count.
Medically reviewed by Youmna DiStefano, MD · Last reviewed September 2026
When does this result need same-day care?
- Markedly prolonged PT with active bleeding, black stools or a severe headache — same-day care
What is the normal range for Prothrombin Time?
- age 18+: 11.0 – 13.5 seconds
Often reflects warfarin therapy, vitamin K deficiency, or liver disease.
Full reference table, citations and testing options: Prothrombin Time biomarker page.
What are the common causes of high Prothrombin Time?
- Warfarin (expected)
- Liver disease, cirrhosis
- Vitamin K deficiency: poor intake, malabsorption, prolonged antibiotics
- Factor VII deficiency (inherited or acquired)
- Disseminated intravascular coagulation, massive transfusion
- Under-filled or delayed sample (false high)
What symptoms go with high Prothrombin Time?
- Easy bruising, nosebleeds, bleeding gums, prolonged bleeding after cuts
- Often none until markedly prolonged
What do clinicians usually check next?
- Repeat with correct collection; INR, aPTT, platelets, fibrinogen
- Liver panel and albumin
- Vitamin K trial or factor assays as directed; hematology if inherited deficiency suspected
Follow-up tests available at TestWell: Vitamin K ($36.99).
How do you recheck Prothrombin Time?
Prices are cash-pay; every order adds one $6 lab processing fee. Physician authorization is included; no insurance or referral needed.
| Test or panel | Type | Price | Fasting | Results |
|---|---|---|---|---|
| Blood Clotting Panel | Panel · 4 tests | $149.99 | No | 3–7 business days |
| Prothrombin Time with INR | Test · 2 biomarkers | $23.99 | No | 1–3 business days |
Common questions
PT vs INR — what's the difference?
INR is the PT standardized so results compare across labs; it's what warfarin dosing uses. A prolonged PT off warfarin is investigated for liver, vitamin K and factor causes.
Educational content, not a diagnosis. Lab results are one input; a clinician interprets them with your history and exam.