Common causes of polyuria include Diabetes mellitus (most common) Arginine vasopressin deficiency Arginine vasopressin resistance (nephrogenic diabetes insipidus) Compulsive or habitual water drinking (primary polydipsia) Diagnosis of Arginine Vasopressin Deficiency Water deprivation test Sometimes vasopressin or copeptin levels Arginine vasopressin deficiency must be differentiated from other causes of polyuria, particularly primary polydipsia (see table) and arginine vasopressin resistance.