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Glucose Tolerance Test (GTT) with Insulins - 3 Hour

Important Note

Male or non-pregnant female
Draw fasting glucose and insulin specimen & finger stick glucose
Give 75 gram glucola
Collect blood at the following intervals:

1 Hour Glucose and Insulin

2 Hour Glucose and Insulin

3 Hour Glucose and Insulin

Icon & Photos

Grey Potassium Oxalate & Lavender EDTA Tube

Specimen Requirements

Preferred:
Container/Tube: Grey Potassium Oxalate & Lavender EDTA Tube for Fasting testing. Same 2 tubes for the 1 hour, 2 hour, and 3 hour testing when needed.
Minimum Volume: 1.0 mL of each tube
Collection Instructions: The patient will have the fasting Glucose and Insulin bloodwork collected then have either a 75g dose of glucola or a meal (**Consult the ordering physician for which.)  Then the patient will be drawn at 1 hour intervals for the 1 Hour, 2 Hour, and 3 Hour glucose and insulin.
Also Acceptable:
Container/Tube: Mint Green Top (Lithium Heparin Gel)

Specimen Stability

Ambient: 8 hours
Refrigerate: 48 hours
Frozen: aliquot for longer storage

Reference Range

Fasting Glucose 70-125 mg/dL
1 hour Glucose 70-199 mg/dL
2 hour Glucose 70-199 mg/dL
3 hour Glucose 70-125 mg/dL
Fasting Insulin 1.9-23.0

uIU/mL
1 hour Insulin No Ref Range  
2 hour Insulin No Ref Range  
3 hour Insulin No Ref Range  

 

The ADA criteria for prediabetes is a fasting plasma glucose of 100-125 mg/dL or 2hr post-glucose sample of 140-199 mg/dl

Methodology

See individual tests for Methodology

CPT

83525(x4),82947,82951

Lab Handling

No finger stick needed. Draw a fasting Glucose and Insulin, a 1 hour Glucose and Insulin, a 2 Hour Glucose and Insulin, and a 3 Hour Glucose and Insulin