A 76-year-old female was admitted to our hospital because of severe diarrhea and lethargy. Diarrhea persisted since several weeks. Past medical history revealed cholecystectomy, appendectomy, coronary artery bypass surgery, and hypertension. Palpation of the right hemi abdomen was slightly painful. No pathologic findings could be detected with abdominal ultrasound, abdominal X-ray, and computed tomography of the cerebrum. Laboratory tests revealed several electrolyte abnormalities. The clinical chemist, however, suspected that a laboratory error had occurred and suggested to repeat the test.