Glucose Tolerance, Gestational Alternative (75 gram 2 Hour Gestational OGTT)

Sunquest Code:GTTG75  
Epic Code:LAB3513Epic Name:Glucose Tolerance Gest Alt 75 GM 2 HR
Methodology:Bichromatic end point, glucose oxidase
Test Includes:Fasting 1 hr, 2 hr. Alternative 75 g glucose during pregnancy. See Glucose Tolerance, Gestational Screen also.
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) (Green (lithium heparin) on ICE, Green (sodium heparin, no gel), Green (sodium heparin, no gel) on ICE, Red (no gel), Red or gold (gel))
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  (Fairview Range - FRMC, UMMC-East Bank, Fairview Lakes - FLMC, Fairview Ridges - FRH, Fairview Northland - FNMC, Fairview Southdale - FSH, UMMC/UMMCH-West Bank)


Reference Range:




Less than 95

1 hour

Less than 180

2 hour

Less than 155

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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