If the history and physical examination are not revealing, a urinalysis should be obtained In almost all cases of polydipsia, the urine-specific gravity will be low (less than 1.010) A specific gravity greater than 1.020 usually represents appropriate thirst If the urinalysis is abnormal, DM (glucosuria, possibly ketonuria, and pseudo-hypersthenuria), sickle cell disease (isosthenuric), or an intrinsic renal disorder (cellular elements and sediment) should be suspected If the urinalysis is normal, electrolytes, calcium, and renal function tests may reveal conditions associated with electrolyte imbalances Patients with poorly controlled DM, DI, or nephrogenic DI may have hypernatremia if they are examined when dehydrated A hemoglobin electrophoresis may be needed to determine whether the patient has sickle cell disease However, patients with sickle cell disease usually have the diagnosis confirmed before the development of tubular dysfunction and polydipsia Because of the high resolution required to diagnose most intracranial causes, magnetic resonance imaging scan is usually necessary