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22914 Osmolality

Osmolality
Test Code: OS
Synonyms/Keywords
 Osmo​
Specimen Requirements
Fasting Required Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)
Pediatric Minimum Volume
(no repeat)
No​ Serum or Plasma​ Red Top Tube (RTT) or Serum Separator Tube (SST)​ Lithium-heparin Plasma Separator Tube (PST), Sodium-heparin Green Top Tube (GTT)​ 1.0 mL​ 0.2 mL​ 0.1 mL​
Collection Processing Instructions
Previously collected specimens are acceptable up to 2 hours on cells. Indicate collection time.
Specimen Stability Information
Specimen Type Temperature Time
​ Serum/Plasma​ ​Ambient ​3 hours
Refrigerated​ 5 days
Frozen​ 3 months
Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
Diagnostic Treatment Center​ ​Monday through Sunday​ ​Less than 2 hours ​Freezing-Point Depression​
​Eau Claire​Monday through Sunday​Less than 2 hours​​Freezing-Point Depression​​
​Flambeau Hospital ​Monday through Sunday​ ​Less than 2 hours ​Freezing-Point Depression​
Marshfield​ Monday through Sunday​ Less than 2 hours​ Freezing-Point Depression​
​NeillsvilleMonday through Sunday​​Less than 2 hoursFreezing-Point Depression​​
Test Information
Calculating osmolality using 2 x Na + BUN/3 + Glucose/20 and subtracting from the measured osmolality gives the osmolal gap. Gaps measured on non-acute outpatients gave values in the range of -5 to +9 using this formula. An elevated osmolality and a gap > 10 suggests the presence of circulating volatiles or other low molecular weight species.​
Reference Range Information
Performing Location Reference Range
All Performing Sites 282 - 305 mOs/kg​
Outreach CPTs
CPT Modifier
(if needed)
Quantity Description Comments
83930​
Synonyms/Keywords
 Osmo​
Ordering Applications
Ordering Application Description
​Centricity ​Osmolality, Blood
​Cerner ​Osmolality
COM​​ ​Osmolality - Blood
If the ordering application you are looking for is not listed, contact your local laboratory for assistance.
Specimen Requirements
Fasting Required Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)
Pediatric Minimum Volume
(no repeat)
No​ Serum or Plasma​ Red Top Tube (RTT) or Serum Separator Tube (SST)​ Lithium-heparin Plasma Separator Tube (PST), Sodium-heparin Green Top Tube (GTT)​ 1.0 mL​ 0.2 mL​ 0.1 mL​
Collection Processing
Previously collected specimens are acceptable up to 2 hours on cells. Indicate collection time.
Specimen Stability Information
Specimen Type Temperature Time
​ Serum/Plasma​ ​Ambient ​3 hours
Refrigerated​ 5 days
Frozen​ 3 months
Reference Range Information
Performing Location Reference Range
All Performing Sites 282 - 305 mOs/kg​
For more information visit:
Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
Diagnostic Treatment Center​ ​Monday through Sunday​ ​Less than 2 hours ​Freezing-Point Depression​
​Eau Claire​Monday through Sunday​Less than 2 hours​​Freezing-Point Depression​​
​Flambeau Hospital ​Monday through Sunday​ ​Less than 2 hours ​Freezing-Point Depression​
Marshfield​ Monday through Sunday​ Less than 2 hours​ Freezing-Point Depression​
​NeillsvilleMonday through Sunday​​Less than 2 hoursFreezing-Point Depression​​
For billing questions, see Contacts
Outreach CPTs
CPT Modifier
(if needed)
Quantity Description Comments
83930​
For most current information refer to the Marshfield Laboratory online reference manual.