This tutorial looks at hypernatremia and hyperosmolar syndrome. Hypernatremia is usually caused by three things: 1) Profound dehydration, 2) Too much sodium intake – most of the time this is due to over-resuscitation with isotonic fluids, 3) Central or Nephrogenic Diabetes Insipidis. I explain how to calculate water deficit and water replacement and how to evaluate and treat patients with diabetes insipidus. @ccmtutorials