Glucose Tolerance, Gestational Standard 3 Hour (100g)

Sunquest Code:GTTG3  
Epic Code:LAB773Epic Name:Gestational Glucose Tolerance 3 Hour
Order Instructions:Fasting: GTTGF, LAB770, PLAB770; 1 Hour: GTTG1, LAB771, PLAB771; 2 Hour: GTTG2, GTTG75, LAB772, PLAB772; 3 Hour: GTTG3, LAB773, PLAB773
Synonyms:GTT; GTTG
Methodology:Bichromatic endpoint, glucose oxide
St Johns/St Joseph/Woodwinds: Hexokinase
Test Includes:Fasting, 1 hour, 2 hour, 3 hour blood glucose. Standard dose is 100 g glucose during pregnancy,
Turnaround Time:Performed Mon-Fri, 0700-1700; turnaround time is 2 hours from the time the last specimen was collected.
Special Instructions:PCU/Clinic can obtain glucose solution from the pharmacy.
Associated Links:

Glucose Tolerance Testing

Collection Instructions

Optimal Volume:2.5 mL
Minimum\Peds Volume:0.6 mL
Container:Green (lithium heparin, gel), St Johns/St Joseph/Woodwinds - Gray Na Fluoride) (Green (lithium heparin, no gel), Red (no gel), Red or gold (gel), St Johns/St Joseph/Woodwinds-Green (lithium heparin, no gel), St Johns/St Joseph/Woodwinds - Red (no gel), St Johns/St Joseph/Woodwinds - Purple (EDTA))
Collection Instructions:
  1. Patient must plan to stay in immediate area and remain quiet.
  2. Measure fasting glucose level before glucose solution is administered. A fasting glucose greater than 126 mg/dL is reported to physician before continuing the test.
  3. Administer oral glucose solution and begin timing immediately after the patient finishes the glucose solution. Patient should finish drinking solution within 10 minutes. Standard dose is 100 grams glucose during pregnancy.
  4. Collect specimens at 1, 2, and 3 hours from time patient finishes the glucose solution. Label each specimen with collection time, patient name, and identification number.
  5. For glucose tolerance blood specimens collected in hospital, deliver to laboratory individually as collected.
Patient Preparation:Please do not eat 10-12 hours before your appointment if you are coming in fasting for labs on lipids, cholesterol, or glucose (sugar). Water, hot tea and black coffee (with nothing added) is okay. Do not drink other fluids, diet soda or chew gum.
If you have concerns about taking your medications, please send a message by clicking on Secure Messaging, Message Your Care Team.  
Contraindications:If patient becomes ill or vomits, test must be discontinued.

Processing and Shipping

Specimen Processing:Centrifuge and aliquot 1.25 mL, 0.2 mL minimum. Store in refrigerator.
Shipping Instructions:Ship at refrigerated temperature.
Stability:Once separated from cells, Room temperature - 8 hours; refrigerated - 72 hours.
Test Performed at or Referral Lab Chemistry  (University of Minnesota Health Maple Grove Clinics, Range, UMMC-East Bank, Oxboro Bloom, Lakes, Ridges, Northland, Southdale, UMMC/UMMCH-West Bank, Clinics, M Health Clinic and Surgery Center, Grand Itasca, St. Joseph's, St. John's, Woodwinds)


Critical Range:
St Johns/St Joseph/Woodwinds <60 mg/dL ≥400 mg/dL
All other sites <40 mg/dL >500 mg/dL
Reference Range:
  All sites:
Fasting >60 and <95 mg/dL
1 hour >60 and <180 mg/dL
2 hour >60 and <155 mg/dL
3 hour >60 and <140 mg/dL
Blood glucose levels collected at fasting, and 1-hour, 2-hours and 3-hours after ingestion of 100 g glucose during pregnancy. A diagnosis of gestational diabetes mellitus may be made if 2 or more of the above results are met or exceeded.

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