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Test Code 8156 Glucose Tolerance Test, 100 G/3 Hour, Pre-Diabetes-Z13.1 (Gestational Diabetes Diagnostic), Plasma

Performing Laboratory

Barnes-Jewish Hospital Laboratory


Enzymatic (Hexokinase)
Literature References:
Package insert: Glucose/HK, Roche Corporation, 1/2006.

Specimen Requirements

Note: This test is to be ordered for pre-diabetes or diabetes screening when the diagnosis code Z13.1 is used.


Patient Preparation:
An 8 to 14 hour fast after 3 days of adequate carbohydrate loading (>150 g/day) is required.


Collection Procedure:
 1. Glucometer pre meter check is not for diagnostic purposes per American Diabetes Association; Diabetes Care:19(Suppl):562-6.

2. This test is used to diagnose gestational diabetes if indicated by screening test.


Obtain glucometer reading and proceed as follows:


If glucometer glucose is <150 mg/dL
1. Draw fasting venous specimen.
2. Give patient 100 g glucose tolerance beverage.
3. Draw venous specimens at 1-, 2-, and 3-hours post consumption.


If glucometer glucose is >150 mg/dL
1. Do not give glucose tolerance beverage.
2. Draw a venous specimen. Send STAT to Barnes-Jewish Hospital Laboratory for #1857 Glucose, Fasting.


If STAT Glucose, Fasting is <140 mg/dL
1. Give patient 100 g glucose tolerance beverage.
2. Draw venous specimens at 1-, 2-, and 3-hours post consumption.


If STAT Glucose, Fasting is >140 mg/dL
Contact physician before proceeding.


Specimen Type: Plasma

Container/Tube: Grey top (potassium oxalate/sodium fluoride)

Specimen Volume: Full tube


Additional Information: Draw times are required.

Day(s) Test Set Up

Monday through Sunday
Turnaround Time:
STAT: 1 hour after receipt in laboratory
Routine: 2 to 4 hours after receipt in laboratory

Reference Values

100 G/3 hour (Gestational Diabetes Diagnostic)

Normal range:  Diagnostic criteria generally require that 2 or more of

the following criteria be met:

Fasting:  ≥ to 95 mg/dL

1 Hour:   ≥ to 180 mg/dL

2 Hour:   ≥ to 155 mg/dL

3 Hour:   ≥ to 140 mg/dL


Reference Interval Info:  Harper,L.M.,et al.  Carpenter-Coustan Compared With National Diabetes Data Group Criteria for Diagnosing Gestational Diabetes.  Obstetrics & Gynecology 2016: 127 (5): 893-898.

Current interpretive data was last revised on 1/9/2017.

Test Classification and CPT Coding

82951TS-Glucose tolerance, 3 specimens
82952TS-Glucose tolerance, each additional specimen

Additional Information

For BJH Laboratory Use Only
Alternate Tube:

1 dark green-top (lithium heparin) tube

1 lavender-top (EDTA) tube

1 mint green-top (lithium heparin) tube

1 red-top tube
Analyte Stability:

See Analyte Stability Chart in Special Instructions.

Laboratory Processing Instructions:
Test performed in BJH Core Lab.  Processed by automated line for delivery to the Cobas 8000. Completed specimens are stored refrigerated for 5 days. 

Specimen Transport Temperature


Special Instructions

LOINC Code Information


Name LOINC Code
Glucose in Blood 2339-0
Fasting Glucose 1558-6
Glucose- 1 hour post 100 g glucose PO 1501-6
Glucose- 2 hours post 100 g glucose PO 1514-9
Glucose- 3 hours post 100 g glucose PO 1530-5