The module on advanced rehydration therapy explains how dehydration occurs, how to assess its severity, and how to treat it using oral rehydration therapy (ORT), including correct preparation and administration of oral rehydration solutions (ORS). It emphasizes that ORT is a life-saving, first-line treatment for fluid and electrolyte loss—especially from diarrhea—and provides practical guidance for both clinical care and low-resource settings, including homemade solutions when commercial ORS is unavailable.