Vitamin K 1 is available for intravenous (IV), subcutaneous, and oral administration. Table 1 provides a brief summary of the advantages and disadvantages for each route of Vitamin K 1 . The subcutaneous route has a delayed onset and is less predictable. 1 If rapid reversal is desired, the IV route should be utilized, as this route is associated with the fastest onset of action. Historically, intravenous vitamin K 1 has been associated with an increased risk of anaphylaxis. A retrospective review of anaphylactic reactions associated with IV vitamin K 1 from the Mayo Clinic revealed that the risk of anaphylaxis with vitamin K 1 was 3 per 10,000 doses—a rate comparable to all forms of penicillin and less than that of IV iron dextran. 4 If is administered by the IV route, lower doses and slower infusion rates are recommended. Unless rapid reversal of the INR is critical, oral vitamin K 1 is the preferred route of administration. In the United States, oral vitamin K 1 is only available as a 5 mg tablet (Mephyton ® ). Therefore, oral doses prescribed should reflect even divisions of 5 mg (., mg).