Urine osmolality reflects how concentrated the urine is. When the body needs to conserve water, healthy kidneys produce highly concentrated urine; when water is plentiful, urine becomes dilute. Abnormal patterns can indicate diabetes insipidus, SIADH, primary polydipsia, kidney disease, and other conditions affecting fluid balance.
This test is used to evaluate excessive thirst and urination, hyponatremia or hypernatremia, suspected diabetes insipidus or SIADH, and unusual urine output patterns. It is typically interpreted alongside serum osmolality, sodium, and other electrolytes. Sample type is a random urine specimen.