In this module, we will discuss polyuria and polydipsia, its causes, and treatments. You will learn a comprehensive diagnostic approach, including the pertinent questions to ask in your history, which physical exams to perform, and what investigations to order. Finally, through clinical cases, you will learn in detail causes and treatment of polydipsia, including osmotic diuresis, diabetes insipidus, both nephrophenic and central, as well as psychogenic polydipsia.