Serum Osmolality

Blood Osmolality Test, Osmolality Test

What To Think About

• Serum osmolality can be calculated by measuring the amounts of sodium, glucose, and blood urea nitrogen (BUN) in the blood.
• The osmolality of urine may be measured and compared to the blood osmolality to help evaluate how well the kidneys work to remove water and chemicals from the blood.
• Sometimes antidiuretic hormone (ADH) increases even though the amount of chemicals in the blood is not high. This is called inappropriate antidiuretic hormone secretion (SIADH). It is sometimes seen in people who use some types of medicine or who have lung disease, cancer, or diseases of the brain and spinal cord. Serum osmolality levels can check to see if SIADH is present.

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Author:	Maria G. Essig, MS, ELS	Last Updated: November 27, 2007
Medical Review:	Caroline S. Rhoads, MD - Internal Medicine David C.W. Lau, MD, PhD, FRCPC - Endocrinology & Metabolism
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