Hypernatremia is much less common than hyponatremia. It is usually produced by a severe water deficit that is considerably greater than the sodium deficit and is most often accompanied by dehydration (see the box on this page). The water deficit can be due to severe water deprivation, severe hypotonic fluid loss (renal or nonrenal) without replacement, or a combination of the two. The serum sodium concentration and serum osmolality are increased. Urine volume is low and urine specific gravity or osmolality are high in water deprivation or in dehydration due to nonrenal water loss. Urine volume is high and urine specific gravity or osmolality is low in dehydration due to water loss through the kidneys. Other laboratory test values may suggest dehydration, and clinical signs of dehydration may be present. Although the serum sodium level is increased, the total body sodium level may be normal or even decreased, the sodium deficit being overshadowed by the water deficit. Occasionally, hypernatremia is caused by excess intake of sodium, which is usually not intentional.