Coagulation
Prothrombin Time
LOINC 5902-2 · s
Ranges
Reference range: 11–13.5 s
What it is
Prothrombin time (PT) measures how long your blood takes to clot through one of its main pathways.
Why it matters
It helps assess bleeding risk and liver function and, as the INR, guides warfarin therapy.
What high values can mean
A higher value (longer time) means slower clotting, from clotting-factor or vitamin-K deficiency, liver disease or blood thinners.
What low values can mean
A lower value is less common and is interpreted in context.
How to improve it
PT reflects clotting function, liver health or medication; it is managed medically, not by lifestyle.
Food & lifestyle
Adequate vitamin K (leafy greens) supports normal clotting, but keep intake consistent if you take warfarin.
Preparing for the test
A blood test; fasting is not required — follow your lab's instructions.
When to talk to a doctor
An abnormal PT is interpreted by a doctor with INR and your bleeding history.
Related markers
Sources
- MedlinePlus (NIH)
- Testing.com (AACC)
Content reviewed on June 26, 2026
Medical disclaimer
This content is for educational purposes only. It is not medical advice and does not diagnose, treat, or prevent any condition. Reference ranges vary between laboratories — always use the range printed on your report and discuss your results with a healthcare professional.
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