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22297 Anion Gap

Anion Gap
Test Code:  
Synonyms/Keywords
Balance, Electrolyte​
Test Components
Sodium, Chloride, Bicarbonate​
Useful For
This calculation is reported on all chemistry panels that contain electrolyte tests and cannot be ordered separately. The Anion Gap calculation: Na - (CL + CO2) = Anion Gap (mmol/L).
 
Known causes of a low anion gap are bromide use (falsely high chloride) or viscosity effects (gives short sample).
 
High anion gaps are seen in acidotic states due to consumption of bicarbonate ion by organic acids leading to increased levels of unmeasured organic anions. ​
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/ Plasma​ Red Top (RTT)
Lithium-heparin Plasma Separator (PST)​		 Lithium or Sodium-heparin Green Top (GTT)
Gold Top (GDTT)​		 1 mL​ 0.3 mL​ 0.6 mL whole blood​
Specimen Stability Information
Specimen Type Temperature Time
Serum/Plasma​ ​ Refrigerate​ 1 week​
Frozen​ >1 week​
Rejection Criteria
Samples collected with Potassium Oxalate/Sodium Fluoride
Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
Bloomer​ ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Cadott ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Chetek ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Chippewa Falls ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Colby/Abbotsford ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Cornell ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Cumberland ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Diagnostic Treatment Center ​​Monday through Sunday​ ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Eagle River ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Eau Claire ​​Monday through Sunday​ ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Flambeau Hospital ​​Monday through Sunday​ ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
Hayward​ ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Ladysmith ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Lake Hallie ​​Monday through Sunday​ ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Lakeview Medical Center ​​Monday through Sunday​ ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Marshfield​ ​Monday through Sunday​ ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Menomonie ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Mercer ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Merrill ​​Monday through Saturday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Minocqua ​​Monday through Sunday​ ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
Mosinee Monday through Friday Less than 2 hours​ Calculation: Na - (Cl +CO2)  ​
​Oakwood ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Phillips ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Stettin ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Stevens Point ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
Wausau​ ​​Monday through Sunday​ ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Wisconsin Rapids ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Wittenberg ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
Reference Range Information
Performing Location Reference Range
All Performing Sites 2-16 mmol/L​
Synonyms/Keywords
Balance, Electrolyte​
Test Components
Sodium, Chloride, Bicarbonate​
Ordering Applications
Ordering Application Description
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/ Plasma​ Red Top (RTT)
Lithium-heparin Plasma Separator (PST)​		 Lithium or Sodium-heparin Green Top (GTT)
Gold Top (GDTT)​		 1 mL​ 0.3 mL​ 0.6 mL whole blood​
Specimen Stability Information
Specimen Type Temperature Time
Serum/Plasma​ ​ Refrigerate​ 1 week​
Frozen​ >1 week​
Rejection Criteria
Samples collected with Potassium Oxalate/Sodium Fluoride
Useful For
This calculation is reported on all chemistry panels that contain electrolyte tests and cannot be ordered separately. The Anion Gap calculation: Na - (CL + CO2) = Anion Gap (mmol/L).
 
Known causes of a low anion gap are bromide use (falsely high chloride) or viscosity effects (gives short sample).
 
High anion gaps are seen in acidotic states due to consumption of bicarbonate ion by organic acids leading to increased levels of unmeasured organic anions. ​
Test Components
Sodium, Chloride, Bicarbonate​
Reference Range Information
Performing Location Reference Range
All Performing Sites 2-16 mmol/L​
For more information visit:
Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
Bloomer​ ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Cadott ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Chetek ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Chippewa Falls ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Colby/Abbotsford ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Cornell ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Cumberland ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Diagnostic Treatment Center ​​Monday through Sunday​ ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Eagle River ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Eau Claire ​​Monday through Sunday​ ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Flambeau Hospital ​​Monday through Sunday​ ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
Hayward​ ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Ladysmith ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Lake Hallie ​​Monday through Sunday​ ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Lakeview Medical Center ​​Monday through Sunday​ ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Marshfield​ ​Monday through Sunday​ ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Menomonie ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Mercer ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Merrill ​​Monday through Saturday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Minocqua ​​Monday through Sunday​ ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
Mosinee Monday through Friday Less than 2 hours​ Calculation: Na - (Cl +CO2)  ​
​Oakwood ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Phillips ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Stettin ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Stevens Point ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
Wausau​ ​​Monday through Sunday​ ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Wisconsin Rapids ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
​Wittenberg ​Monday through Friday ​Less than 2 hours​ ​Calculation: Na - (Cl +CO2) ​
For billing questions, see Contacts
For most current information refer to the Marshfield Laboratory online reference manual.