INR / Prothrombin Time Interpretation
Interprets INR (International Normalised Ratio) and PT (Prothrombin Time) in clinical context: anticoagulation, liver disease, coagulopathy.
Score interpretation
INR up to 1.2: normal without anticoagulation; below the therapeutic range on warfarin.
→ Not anticoagulated: normal. On warfarin: check adherence, interactions and dosing with the anticoagulation service.
INR above 1.2 and below 2.0: raised without anticoagulation; below the 2.0–3.0 range on warfarin.
→ Not anticoagulated: look for a cause (liver disease, vitamin K deficiency, DIC, factor deficiency, drugs). On warfarin: review with the anticoagulation service.
Within the 2.0–3.0 range for a target INR of 2.5 (VTE, AF; BCSH 2011).
→ Continue; compare with the patient's own target (some mechanical valves need a target of 3.0 or higher).
Above the 2.0–3.0 range. Some patients (e.g. some mechanical valves) have a target of 3.0 or higher.
→ Compare with the patient's own target; if above it, review the warfarin dose with the anticoagulation service and assess for bleeding.
INR 5.0–8.0: increased bleeding risk.
→ BCSH: without bleeding, withhold warfarin and review the maintenance dose; if bleeding, urgent review and reversal per BCSH / local protocol.
INR above 8.0: high bleeding risk.
→ BCSH: stop warfarin and give vitamin K per BCSH / local protocol; emergency reversal if bleeding.
Interpretation bands for the INR Interpretation. Apply clinical judgement and local guidance.
References
- Keeling D, et al. Guidelines on oral anticoagulation with warfarin – fourth edition. Br J Haematol. 2011;154(3):311-324.
Related
Curated clinical cross-links plus same-class fallbacks.
- Prothrombin Complex Concentrate (PCC) · Coagulation Factor Concentrate — Warfarin Reversal
- Warfarin · Anticoagulant
- Bivalirudin (PCI Anticoagulation) · Direct Thrombin Inhibitor / PCI
- Vasopressin / Terlipressin · Vasopressin Analogue — Vasodilatory Shock / Variceal Bleeding
- Bivalirudin · Anticoagulation
- Warfarin · Vitamin K Antagonist (Anticoagulant)
- Major Haemorrhage / Massive Transfusion · BCSH; RCOA; RCEM; RCS — BCSH Guidelines
- Anaemia Investigation · BSH / NICE
- Splenomegaly Workup · BSH; BMJ Best Practice
- Deep Vein Thrombosis Diagnosis and Treatment · NICE CG144 / NICE NG158
- Sickle Cell Crisis · BSH 2021 / BCSH
- Neutropenic Sepsis · NICE CG151 2012 / ESMO
Decision support only — verify against a current formulary, NICE, or your local guideline before clinical use.