How frequently should INR monitoring be performed during the first few weeks of warfarin therapy?

INR monitoring during the first few weeks of warfarin therapy should be performed frequently, typically every 2 to 3 days initially, until the INR is stable within the therapeutic range. This close monitoring allows for timely dose adjustments to achieve and maintain the target INR, reducing the risk of bleeding or thrombosis. Once stable, the interval between INR tests can be gradually extended to weekly and then to longer intervals as clinically appropriate.

This approach is supported by UK guidelines, which recommend frequent INR checks early in therapy to ensure safe and effective anticoagulation ¹. Similarly, clinical literature emphasizes that during warfarin initiation, INR should be monitored every 2 to 3 days due to the drug’s variable pharmacokinetics and interactions, until a stable dose is established (Hawes and Viera, 2014).