Black licorice ingestion: Yet another confounding agent in patients with melena.

We describe an 80-year-old woman with atrial fibrillation, anti-coagulated with warfarin, who on two separate occasions developed black tarry stools and an elevated international normalized ratio (INR) after eating a pound of Black Licorice. During her most recent episode, her hematocrit was 14 (baseline 34) and her INR was 5.5 (baseline 2.