Can this result diagnose a condition on its own?

No. Laboratory results are interpreted with symptoms, medical history, specimen conditions and related tests.

Which reference range should I use?

Start with the performing laboratory's own reference interval; clinical cutoffs, when relevant, are separate sourced thresholds used for a specific purpose.

When should I discuss the result with a healthcare professional?

Results that are clearly outside range, persistent, symptomatic or unexpected should be reviewed by a healthcare professional.

Information about a laboratory test

INR: What Does This Test Measure?

The INR test measures the standardized ratio derived from prothrombin time so results can be compared across methods and laboratories.

Test summary

Test name: INR
Abbreviations: INR
Category: Coagulation
Panel: Coagulation / Anticoagulation Monitoring
Specimen: Citrated plasma
Common units: ratio

What does the test measure?

The INR test measures the standardized ratio derived from prothrombin time so results can be compared across methods and laboratories.

Why is the test ordered?

It may be ordered to investigate abnormal bleeding or clotting, assess coagulation before procedures, or monitor selected anticoagulant therapies.

Information about a low result

A low INR may mean that a person taking warfarin is below their intended target, but targets vary by indication and the result should not be used alone to change medication.

Information about a high result

A high INR indicates slower clotting. In people taking warfarin, an INR above the usual non-anticoagulated range may be intentional; targets depend on indication and medication changes require clinical supervision.

Reference and clinical context

Start with the performing laboratory's reference interval, unit, specimen type and method. Numeric information on this page is stored as sourced example intervals or clinical thresholds.

Reference range 1

>= 0.8 – <= 1.1 ratio

Population: Adults not taking warfarin
Age range: 18
Specimen: Citrated plasma

Example INR interval without warfarin

This is sourced reference/clinical-context information and should not be used alone as a diagnosis or treatment decision. The laboratory report, medication use and clinical context take priority.

Reference context 2

>= 2 – <= 3 ratio

Population: Adults taking warfarin / common treatment target
Age range: 18
Specimen: Citrated plasma

Common warfarin INR target context

This is sourced reference/clinical-context information and should not be used alone as a diagnosis or treatment decision. The laboratory report, medication use and clinical context take priority. Warfarin dose must not be changed by the patient based on this table.

Reference ranges may vary by laboratory, method used, age, sex, pregnancy status, and clinical context. The reference range on your own laboratory report takes precedence.

Interpretation notes

The meaning of INR changes substantially with anticoagulant use. During warfarin therapy, target range depends on the individual indication and patients should not adjust doses on their own.

Related specialties

Hematology
Internal Medicine
Cardiology

Frequently asked questions

More information about this test

Sources

Prothrombin Time Test and INR (PT/INR) — U.S. National Library of Medicine (MedlinePlus)
Government medical reference · 2024 · PT/INR purpose, anticoagulation and coagulation interpretation · Verified: Aug 12, 2026
Prothrombin time (PT) — U.S. National Library of Medicine (MedlinePlus)
Government medical encyclopedia · 2025 · Example PT and INR intervals and common warfarin target context · Verified: Aug 12, 2026
Partial Thromboplastin Time (PTT) Test — U.S. National Library of Medicine (MedlinePlus)
Government medical reference · 2026 · aPTT/PTT purpose, prolonged and shortened result context · Verified: Aug 12, 2026