International Normalised Ratio
Haematology marker
INR
International Normalised Ratio
A standardised expression of the prothrombin time that corrects for differences between laboratory reagents. Used mainly to monitor warfarin (vitamin K antagonist) therapy and to assess liver synthetic function.
PED Notes
INR is not a PED marker, but it is the standard way to report prothrombin time and to gauge liver synthetic capacity, which is relevant for oral 17-alpha-alkylated AAS users. A rising INR off anticoagulation can signal impaired hepatic clotting factor synthesis. Note the direction of risk: androgen use raises clotting risk (through elevated haematocrit and a prothrombotic shift), whereas a HIGH INR reflects slower clotting and bleeding risk, so the two are not opposites of the same axis. No PED shifts the healthy target; the bodybuilder range equals the standard range.
When high
When elevated (>1.2 off anticoagulation):
- Off warfarin, an INR above the reference range points to reduced clotting factor synthesis: liver disease, vitamin K deficiency, or disseminated intravascular coagulation.
- What to do: check liver function and albumin. In an AAS user on orals, a rising INR with abnormal liver enzymes is a signal to stop hepatotoxic orals and support recovery.
- On warfarin, a high INR means over-anticoagulation and bleeding risk; dose adjustment and (if very high or bleeding) vitamin K are managed by the prescribing clinician. Never self-adjust.
When low
When low (<0.8):
- A low INR on warfarin means under-anticoagulation and inadequate clot protection; the prescriber will adjust the dose.
- Off anticoagulation, an INR at or slightly below 1.0 is normal. In enhanced athletes the relevant clot risk is driven by haematocrit and the prothrombotic effects of androgens, not by a low INR, so manage those directly.
History Chart
Reading History
Frequently Asked Questions
Reference Ranges
Standard Range
VitalMetrics Range