At what level of serum osmolality is hyponatremia clinically significant?

Updated: Jun 17, 2019
  • Author: Eric E Simon, MD; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Generally, hyponatremia is of clinical significance only when it reflects a drop in the serum osmolality (ie, hypotonic hyponatremia), which is measured directly via osmometry or is calculated as 2(Na) mEq/L + serum glucose (mg/dL)/18 + BUN (mg/dL)/2.8. Note that urea is not an effective osmole, so when the urea levels are very high, the measured osmolality should be corrected for the contribution of urea.

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