A male client is admitted for observation because he is reporting progressively increasing fatigue over the past month and a brief episode of dizziness that occurred today. He has a history of heartburn and indigestion that he self-treats with ibuprofen and antacids. Which assessment finding should the nurse report immediately to the healthcare provider? (Reference ranges: Hemoglobin 14--18 g/dL; Hematocrit 42%--52%; Gastric pH 1.5--3.5.)