A 90-year-old female presented with vomiting, loose stools and dehydration. Laboratory tests revealed electrolyte abnormalities, anemia, and atrial fibrillation. She was diagnosed with acute gastroenteritis, anemia, and atrial fibrillation. She was treated with antibiotics, antiemetics, proton pump inhibitors, and antiarrhythmics. The pharmacist intervened to advise on diagnosing and treating the patient's anemia.