Polyuria

Polyuria is a condition usually defined as excessive or abnormally large production or passage of urine (greater than 2.5 or 3 L over 24 hours in adults). Frequent urination is sometimes included by definition but is nonetheless usually an accompanying symptom. Increased production and passage of urine may also be termed diuresis.

Polyuria often appears in conjunction with polydipsia, though it is possible to have one without the other, and the latter may be a cause or an effect. Psychogenic polydipsia may lead to polyuria.

Although they have a common name, diabetes mellitus and diabetes insipidus are two entirely separate conditions with unrelated mechanisms. Both cause large amounts of urine to be produced (polyuria), and the term “diabetes” is derived from the Greek word meaning siphon. However, diabetes insipidus is either a problem with the production of antidiuretic hormone (central diabetes insipidus) or kidney's response to antidiuretic hormone (nephrogenic diabetes insipidus), whereas diabetes mellitus causes polyuria via a process called osmotic diuresis, due to the high blood sugar leaking into the urine and taking excess water along with it.