Alberta Precision Laboratories

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Test Name/Synonym:

Gestational Diabetes Screen - Calgary Zone (CLS)

Test Code:

GESTSC

Primary Container:

See Collection Information Below

Specimen Collection 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.
One 3 mL or 4.5 mL light green (mint) top PST tube. Gold top SST tube also acceptable.

0.2 mL plasma or serum

Calgary Zone: Microcollection Minimum Whole Blood Volumes.

Reference Interval:

Test should be performed between 24-28 weeks gestation and should not be performed at or after 35 weeks of gestation. Fasting blood glucose and/or Hemoglobin A1C (HbA1c) are the recommended tests at or after 35 weeks gestation. Please click here for further information.
A glucose tolerance test is warranted if the 1 hour glucose value is 7.8 mmol/L up to and including 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.

Testing Area:

Chemistry

Performing Site:

Chemistry-DSC, FMC, PLC, RGH, SHC
Rural: CRL

Additional Test Information:

Guidelines suggest testing between 24th and 28th week of gestation. Test should not be performed at or after 35 weeks of gestation. Fasting Blood Glucose and/or Hemoglobin A1c (HbA1c) are the recommended tests at or after 35 weeks gestation. Please click here for further information.

Please indicate number of weeks gestation on the requisition.

The drink provided for this test includes the following ingredients:

Patient Service Centre and Calgary Hospital Sites	Calgary Rural Lab Sites
Dextrose/Glucose (derived from corn) Citric acid Artificial flavours Sodium benzoate FD&C Yellow #6 Purified water	Dextrose/Glucose (derived from corn) Citric acid Natural orange flavouring Sodium benzoate FD&C Yellow #6 FD&C Red #40 Purified water

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.

Last Updated On:

Thursday, March 19, 2026