---
title: "What does a high Prothrombin Time mean?"
type: biomarker-interpretation
url: "https://www.test-well.com/biomarkers/prothrombin-time/high"
biomarker: Prothrombin Time
direction: high
reference_range:
  - "age 18+: 11.0 – 13.5 seconds"
reviewed_at: 2026-09-08
review_status: reviewed
date_published: 2026-09-05
---

# What does a high Prothrombin Time mean?

> 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.


## 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.

## What are the common causes of high Prothrombin Time?

1. Warfarin (expected)
2. Liver disease, cirrhosis
3. Vitamin K deficiency: poor intake, malabsorption, prolonged antibiotics
4. Factor VII deficiency (inherited or acquired)
5. Disseminated intravascular coagulation, massive transfusion
6. 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 at TestWell: [Vitamin K](https://www.test-well.com/tests/vitamin-k-test) ($36.99).

## How do you recheck Prothrombin Time?

| Test or panel | Type | Price | Fasting | Results |
| --- | --- | --- | --- | --- |
| [Blood Clotting Panel](https://www.test-well.com/tests/blood-clotting-panel) | Panel (4 tests) | $149.99 | No | 3–7 business days |
| [Prothrombin Time with INR](https://www.test-well.com/tests/prothrombin-time-inr) | Test | $23.99 | No | 1–3 business days |

Plus one $6 lab processing fee per order; physician authorization included.

## 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.

## Related

- [Prothrombin Time reference ranges](https://www.test-well.com/biomarkers/prothrombin-time)
- [Glucose reference range](https://www.test-well.com/biomarkers/glucose)
- [Creatinine reference range](https://www.test-well.com/biomarkers/creatinine)
- [eGFR reference range](https://www.test-well.com/biomarkers/egfr)

## Sources

- [AACC Lab Tests Online](https://www.testing.com/tests/prothrombin-time-and-international-normalized-ratio-pt-inr/)
- [MedlinePlus (NIH) — Prothrombin Time Test and INR (PT/INR)](https://medlineplus.gov/lab-tests/prothrombin-time-test-and-inr-ptinr/)

---

Medically reviewed by Youmna DiStefano, MD (Medical Reviewer, TestWell); last reviewed 2026-09-08. Review policy: https://www.test-well.com/editorial-policy

Canonical page: https://www.test-well.com/biomarkers/prothrombin-time/high
Machine-readable catalog: https://www.test-well.com/api/catalog.json · MCP server: https://www.test-well.com/mcp · Overview for agents: https://www.test-well.com/llms.txt

Prices are cash-pay, in USD, and include physician authorization; every order adds one flat $6 lab processing fee. Educational content is not a diagnosis — discuss results with a clinician.