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Glucose Tolerance Test

Alternative Names:GTT
Laboratory:Clinical Biochemistry
Test Code:GTT
Specimen Types:Plasma
Container Types:
Fluoride Oxalate
Adults Volume or Mass:5 mL
Minimum/Paediatric Volume or Mass:1 mL
Collection & Request Instructions:Fast for > 8 hours pre procedure

Clinical Use, Protocol and Interpretation.

Transport Instructions between Sites and/or Laboratories:Room Temperature
Assay Frequency:24/7
MBS Rebatable:Yes
MBS Item No.:66542
Additional Notes:

The following Table summarises the 2006 WHO recommendations for the diagnostic criteria for diabetes and intermediate hyperglycaemia.

Diabetes

Fasting plasma glucose      >/=  7.0 mmol/L

OR      2 hr plasma glucose  >/= 11.1 mmol/L              

Impaired Glucose Tolerance

Fasting plasma glucose *    <7.0 mmol/L 

and

2 hr plasma glucose *     >/= 7.8 mmol/L and <11.1 mmol/L

Impaired Fasting Glucose

Fasting plasma glucose         6.1 to 6.9 mmol/L

and (if measured)

2 hr plasma glucose *           <7.8 mmol/L

* Venous plasma glucose 2 hrs after ingestion of 75g oral glucose load

 

DIAGNOSIS of Gestational Diabetes and Diabetes mellitus in pregnancy

* Venous plasma glucose 2 hrs after ingestion of 75g oral glucose load

Fasting

Glucose

mmol/L
 

1hr

Glucose

mmol/L

2 hr

*Glucose

mmol/L

 

               Interpretation      

 

<5.3

AND

< 10.6

AND

< 9.0

Normal Glucose Tolerance

5.3-6.9 

 

OR

≥ 10.6

OR

9.0-11.0

Consistent with gestational diabetes

≥ 7.0

 

 

OR

≥ 11.1

Consistent with overt diabetes in pregnancy

From 4th August 2025, glucose thresholds and early screening recommendations for the diagnosis of Gestational Diabetes are based on ADIPS 2025.

Ref: Sweeting A et al. AIPS consensus recommendations, MJA 2025