The use of vitamin K in patients with warfarin over-anticoagulation lowers excessively elevated INR faster than withholding warfarin alone; however, it has not been clearly demonstrated that vitamin K treatment does, in fact, lower the risk of major hemorrhage. As vitamin K administration via the intravenous route may be complicated by anaphylactoid reactions, and via the subcutaneous route by cutaneous reactions, oral administration is preferred. A dose of 1-2.5mg of oral phytomenadione (vitamin K(1)), reduces the range of INR from 5.0-9.0 to 2.0-5.0 within 24-48 hours, and for an INR >10.0, a dose of 5mg may be more appropriate.
Source: The use of vitamin K in patients on anticoagulant therapy: a practical guide – PubMed