rsi ad
drx ad
ad space

Osmol Gap Calculator


Osmol gap calculator calculates the difference between measured serum osmolality and calculated serum osmolarity.

Osmol gaps are used as a screening tool to identify toxins. Causes of an elevated osmol gap are numerous. Generally there are 4 main causes for an increased osmolar gap: by alcohols, sugars, lipids, or proteins.


Osmol Gap Calculator
Enter serum sodium Na+ (136-145 mEq/L): mmol/L (mEq/L)
Enter serum glucose ((70-99 mg/dL): mg/dL
Enter serum BUN (7-18 mg/dL): mg/dL
Enter measured osmolality (275-295 mosm/L): mosm/L


Based on the formula:

Calculated osmolarity = [2 x Na+] + glucose/18 + BUN/2.8


Calculated osmolarity = mOsm/L

Na+ = mmol/L

glucose = mg/dL

Blood urea nitrogen (BUN) = mg/dL

Osmol gap = Measured osmolality - Calculated osmolarity

0 to +10: Normal osmol gap

>10: Abnormal

<0: Probable lab or calculation error

Drugs Causing Osmolar Gap:


Ethylene glycol


Isopropanol (acetone)






Copyright © 2007-2016 Drug Information, LLC.

Legal Notices and Disclaimer

All calculator information provided by the is for educational purposes only. This information should not be used for the diagnosis or treatment of any health problem or disease and IS NOT INTENDED TO REPLACE CLINICAL JUDGMENT OR GUIDE INDIVIDUAL PATIENT CARE IN ANY MANNER.

Rev 06/16