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Anticoagulation - oral - Management
What should I do if the INR is not in the therapeutic range?

  • If the international normalized ratio (INR) is outside the therapeutic range, ask the person about any changes, including:
    • Their routine for taking warfarin.
    • Other medicines prescribed and purchased.
    • Use of alcohol.
    • General health. (Weight loss, acute illness, and smoking cessation can increase the effect of warfarin. Weight gain, diarrhoea, and vomiting can reduce the effect of warfarin.)
  • If the INR is high:
    • Ask the person if they have any signs of bleeding (see Information and advice). If they have significant bleeding, refer urgently for intravenous treatment with phytomenadione (vitamin K1).
    • Depending on the INR, the warfarin dose may need to be reduced and/or one or two doses may need to be omitted — the INR should then be measured 2 or 3 days later to ensure that it is falling.
      • INR > 8.0 and no bleeding or minor bleeding — stop warfarin and refer urgently for intravenous or oral phytomenadione. For further information on phytomenadione dosage see the warfarin summary of product characteristics (www.emc.medicines.org.uk).
      • INR 6.0 to 8.0 and no bleeding or minor bleeding — stop warfarin. Restart when INR < 5.0.
      • INR < 6.0 but more than 0.5 units above target value — reduce dose or stop warfarin. Restart when INR < 5.0.
  • If the INR is low:
    • Ask the person if they have missed any doses.
    • Depending on the INR, the warfarin dose may need to be (temporarily) increased, and sometimes a booster dose may be required — the INR should then be measured 2 or 3 days later to ensure that it is increasing.

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