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PT / INR: normal range & what your result means

PT (prothrombin time) and its standardised form, INR, measure how quickly your blood clots. INR is used to monitor blood thinners like warfarin.

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Typical adult reference range

Measure	Range
PT	≈ 11–13.5 seconds
INR (not on warfarin)	0.8–1.1
INR (typical warfarin target)	2.0–3.0

What a HIGH result can mean

A high INR means blood is clotting too slowly — higher bleeding risk (over-anticoagulation, liver disease, vitamin K lack)

What a LOW result can mean

A low INR on warfarin means under-treatment — higher clotting risk

Ranges vary by lab. Reference ranges are TYPICAL ADULT values and vary by laboratory, age, sex, pregnancy and the method used. Always read your result against the range printed on YOUR report, and let your doctor interpret it alongside your history.

Frequently asked questions

What INR should I aim for on warfarin?

Most people target an INR of 2.0–3.0, though some conditions need a higher range. Your clinic sets and monitors your target and adjusts the dose.

What raises my INR unexpectedly?

Some antibiotics, alcohol, illness, and changes in diet (vitamin K in leafy greens) can shift INR. Regular monitoring catches these changes.

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MedDroid is an AI medical assistant and can make mistakes. It provides general health information, not a diagnosis or medical advice — always consult a qualified clinician. In an emergency, contact your local emergency number immediately.