Raised INR

Severity

Range

Mild
INR 4.5–6.0, no bleed
Moderate
INR 6.0–8.0, no bleed
Severe
INR > 8.0 or any major bleed

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Anticoagulants Causes

Warfarin over-anticoagulation (commonest)DOAC accumulation in AKI / overdose (apixaban, rivaroxaban, dabigatran, edoxaban)Heparin / LMWH (mainly APTT but contributes)

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Drug interactions Causes

Antibiotics — metronidazole, ciprofloxacin, clarithromycin, co-trimoxazoleAntifungals — fluconazole, miconazole gelAmiodarone, statins (fluvastatin)NSAIDs (potentiate bleeding, not INR)Acute alcohol binge

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Hepatic Causes

Acute liver failure (paracetamol, viral, ischaemic)Cirrhosis with decompensationCholestasis with vit K malabsorption

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Nutritional / GI Causes

Vit K deficiency — poor intake, malabsorption, biliary obstructionProlonged broad-spectrum antibiotics (gut flora)TPN without vit K

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Consumptive / haematological Causes

DIC (sepsis, malignancy, obstetric)Massive transfusion / dilutional coagulopathyLiver disease + sepsis combined