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Gestational Diabetes Screen

Source Blood
Mnemonic GESTSC
Specimen Requirements

Test cannot be collected by Mobile Collection Service (MCS).

Fasting status not required.

50 gram glucose drink to be administered to patient.
Blood sample is collected one hour later.

1 x 3 mL or 4.5 mL light green (mint) top PST tube.  Gold top SST tube also acceptable.

0.2 mL plasma or serum

Minimum Whole Blood Volumes for Microcollections

Specimen Handling
Additional Information

Guidelines suggest testing between 24th and 28th week of gestation.

Please indicate number of weeks gestation on the requisition.

The drink provided for this test includes the following ingredients:

  • Glucose
  • Citric acid
  • FD&C Yellow #6
  • Natural flavours        
  • Sodium benzoate

An unflavored drink which contains no dyes and includes potassium sorbate instead of sodium benzoate as a preservative is also available at Patient Service Centres.

For Diabetes Clinical Practice Guidelines, please see: Canadian Diabetes Association 2013 Clinical Practice Guidelines.

Testing Location Chemistry-DSC, FMC, PLC, RGH, SHC
Rural: CRL
Testing Frequency Daily
Alternate Name(s)  
Reference Interval Test should be performed between 24-28 weeks gestation.  A glucose tolerance test is warranted if the 1 hour glucose value is 7.8 - 11.0 mmol/L.  Gestational diabetes mellitus is diagnosed if the 1 hour glucose value is greater than or equal to 11.1 mmol/L.  Please see Canadian Diabetes Association 2013 practice guidelines.