Obscure gastrointestinal (GI) bleeding is often challenging for the primary care physician, but with improved diagnostic testing the cause of this blood loss is determined in most patients. However, approximately 5% of the time no underlying cause is found. One common etiology in patients younger than 40 years of age is a Meckel's diverticulum. The technetium 99m pertechnetate scan is the standard test for making this diagnosis. However, the sensitivity of the scan is only 62% in the adult population. In this case report, a patient with profound, hemodynamically significant GI blood loss had multiple negative studies. Subsequently, an abnormal vascular lesion was detected and during exploratory laparotomy, a Meckel's diverticulum was found and removed. Although the technetium pertechnetate scan is falsely negative in a number of cases, there are ways to increase its sensitivity and possibly avoid repeated testing.