Osmolality measures the amount of dissolved particles within the blood, which is an indirect measurement of the amount of water within the blood. Dehydration results in increased concentration of particles and low blood fluid levels; while too much fluid in the blood results in decreased concentration of particles. High osmolality blood levels are used to diagnose diabetes insipidus (DI), high calcium levels, high blood sugar (glucose) levels, high blood sodium levels, and kidney disease. Low blood levels are seen in people with low blood calcium, sodium, or glucose levels, lung cancer, or too much fluid intake. For people who are in a coma, monitoring osmolality levels is very important, since excessively high blood (and/or urine) osmolality levels are associated with severe and dangerous seizures that can lead to death. Blood osmolality levels are usually run together with urine osmolality levels. The normal urine and blood osmolality ratio is 1:3.
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