Diabetes insipidus is a syndrome that associates both hypotonic polyuria and polydipsia, due to insufficient or ineffective arginine vasopressin (AVP) synthesis, or to AVP resistance. The diagnosis between central/renal origin, or an abnormal thirst regulation (primary polydipsia) is required to organize an adapted management. Because water deprivation tests are not reliable, it's often based on medical history, response to treatment and MRI. Copeptin is an AVP precursor which could be very helpful for the diagnosis. Its basal dosage may identify nephrogenic DI whereas osmotic stimulated dosage would discriminate central DI and primary polydipsia. Central DI is quite frequent after pituitary surgeries or traumatic brain injuries, and often transient. In case of early diagnosis and familial history of DI, a mutation of AVP gene is suspected, most of the time autosomal dominant. MRI is required to identify the other causes, i.e. tumors and inflammatory diseases (sarcoidosis, histiocytosis, hypophysitis). An advanced evaluation is required before idiopathic DI be retained, especially if a thickening of pituitary stalk is observed. The treatment of central DI is mainly based on lyophilisate of desmopressin administration.