A female patient with atrial fibrillation has the following lab results: Hemoglobin of 11 g/dl, a platelet count of 150,000, an INR of 2.5, and potassium of 2.7 mEq/L. Which result is critical and should be reported to the physician immediately?

1. Hemoglobin 11 g/dl
2. Platelet of 150,000
3. INR of 2.5
4. Potassium of 2.7 mEq/L