Snapshot A 31-year-old female presents to the clinic complaining of intermittent diarrhea for the past 2 months. She endorses bloating, cramping, and flatulence during these episodes but denies any hematochezia or melena. When ask about any clear precipitating factors, she reports that it is usually following yogurt or cheese intake. Introduction Presentation Symptoms abdominal pain bloating flatulence diarrhea vomiting Studies Diagnostic testing diagnostic approach diagnosis is primarily based on clinical presentation studies lactose-free diet diagnostic and therapeutic lactose breath hydrogen test best confirmatory test rise in breath hydrogen following ingestion of lactose is considered diagnostic oral lactose load best initial test observation for symptoms following lactose load small bowel biopsy rarely performed due to invasive nature helps distinguish primary and secondary lactase deficiency Differential Celiac disease distinguishing factors clinical history of gluten ingestion with symptoms negative breath testing results Treatment First-line dietary lactose restriction enzyme replacement commercially available lactase enzyme preparations are available to take orally with lactose-containing food Complications Electrolyte abnormalities