Glucose Tolerance, Gestational Alternative 2 Hour (75g)

Sunquest Code:GL275  
Epic Code:LAB772Epic Name:Gestational Alternative 2 Hr GTT, 2 Hour Post
Order Instructions:Fasting: GLF, LAB772, LAB1144; 1 Hour: GL175, LAB772, PLAB1145; 2 Hour: LAB772, PLAB1146
Methodology:Bichromatic endpoint, glucose oxidase
St Johns/St Joseph/ Woodwinds: Hexokinase
Test Includes:Fasting and 2 hour glucose
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)
[Alternate Containers: 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:
  • Patient must plan to stay in the immediate area and remain quiet.
  • Measure fasting glucose level before glucose solution is administered. No caloric intake is required. Coffee, diet soda or gum are not allowed during fasting period. A fasting glucose greater than 126 mg/dL is reported to the physician before continuing the test.
  • Administer oral glucose solution and begin timing as patient finishes the glucose solution. Patient should finish drinking the solution within 10 minutes. Alternative dose is 75 grams glucose during pregnancy.
  • Collect specimens at 1 and 2 hours from time patient finishes the glucose solution. Label each specimen with collection time, patient name, and identification number.
  • For glucose tolerance blood specimens collected in hospital, deliver to laboratory individually as collected.
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:When clinic schedules test obtain patient name, ID number, age, physician, and tolerance information. Confirm that patient is pregnant. Outpatient laboratory will collect in green top (heparin) or red/black (gel) tubes to avoid hemolysis. Clinics should collect in gray top (NaF) tubes because tubes may not be delivered promptly. 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 mgdL >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
Blood glucose levels collected at fasting; 1 hour and 2 hour after ingestion of 75 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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