What it means
Osmolality counts the particles, such as sodium, urea and glucose, dissolved in a kilogram of water. In urine, it shows how well the kidneys concentrate or dilute it. A low-intake day gives concentrated urine and a high value; drinking a lot gives dilute urine and a low value. It is more exact than urine specific gravity and is often compared with the serum osmolalitySEER-um oz-moh-LAL-ih-teeA blood test that measures how concentrated the blood is, by the amount of dissolved particles in it.Full entry to sort out sodium and water problems.
For the nurse
Record recent fluid intake and any IV fluids or diuretics, because they change the result. A timed or first-morning sample may be ordered.
At a glance
| Normal range | Random sample: about 300–900 mOsm/kg [300–900 mmol/kg]; it can range from about 50 to 1,200 depending on fluid intake. |
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Related terms
dehydration
A state in which the body has lost more water than it has taken in.
creatinine
A waste product of muscle that the kidneys remove from the blood; its blood level is used to measure how well the kidneys work.
serum osmolality
A blood test that measures how concentrated the blood is, by the amount of dissolved particles in it.