The international normalized ratio (INR) is 1.5. What action should the nurse take?

• A. Administer an additional dose of warfarin (Coumadin)
• B. Hold the next dose of warfarin (Coumadin)
• C. Increase the heparin drip rate
• D. Administer Protamine Sulfate

Answer: (A)

An adequate INR is essential for therapeutic anticoagulation with warfarin; when the INR is subtherapeutic, the dose needs to be adjusted to reach the target range. An INR of 1.5 is below the typical goal (about 2.0–3.0 for most indications), so the appropriate action is to give an additional dose of warfarin (or increase the dose per protocol) to bring the INR up toward therapeutic levels. Holding the dose would keep the patient under‑anticoagulated. Protamine sulfate reverses heparin, not warfarin, so it isn’t indicated here, and increasing a heparin drip would not correct subtherapeutic warfarin effect. After adjusting the warfarin dose, recheck the INR as per protocol and monitor for factors that could affect dosing, such as missed doses, dietary vitamin K, or interacting drugs.