What is urine osmolality

Test Catalog. Download Test. Useful For Suggests clinical disorders or settings where the test may be helpful Assessing the concentrating and diluting ability of the kidney as part of the urinalysis panel. Only orderable as a reflex. With dehydration, the urine osmolality should be 3 to 4 times the plasma osmolality. To collect your urine, the health care provider may give you a special clean-catch kit that contains a cleansing solution and sterile wipes. Follow instructions exactly. Your provider may tell you that you need to limit your fluid intake 12 to 14 hours before the test.

Your provider will ask you to temporarily stop taking any medicines that may affect the test results. Be sure to tell your provider about all the medicines you take, including dextran and sucrose. DO NOT stop taking any medicine before talking to your provider. Osmolality is a more exact measurement of urine concentration than the urine specific gravity test. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples.

Talk to your provider about the meaning of your specific test results. Levels of the following commonly affect blood osmolality: salt, or sodium, which is one of the most important electrolytes in blood and urine alcohol toxins sugar. What is the purpose of a urine osmolality test? Preparing for the urine osmolality test. The procedure. What do the results mean? Read this next. Blood Osmolality Test. Medically reviewed by Stacy Sampson, D. Medically reviewed by Carissa Stephens, R. Medically reviewed by Daniel Murrell, M.

Medically reviewed by Debra Rose Wilson, Ph. Medically reviewed by Carolyn Kay, M. Cystocele: What You Need to Know. Medically reviewed by Fernando Mariz, MD. Urine pH Level Test.

ADH Therapy : Arginine vasopressin : rapidly determine patient response. Urine osmolality is usually used to evaluate: renal function, activity, polyuria and oliguria. Healthy kidneys can concentrate urine to an osmolality 4 times greater than serum. Patients with impaired renal function may not be able to concentrate urine. In the healthy system, osmoreceptors in the hypothalmus sense the diffusion of water into or out of receptor cells caused by changes in serum osmolality. In response, the hypothalamus directs the pituitary to increase or decrease the release of vasopressin from the posterior pituitary.

The release of vasopressin causes increased water resorption in the distal tubules and collecting ducts of the kidney. This reduces water loss and concentrates urine. Therefore, dehydration increases vasopressin release leading to water conservation and urine concentration. Fluid overload decreases vasopressin release which leads to diuresis. Panic values for serum osmolality are values of less than mOsm or greater than mOsm.