Glucose Tolerance, Gestational Standard 3 Hour (100g)

Sunquest Code:GTTG  
Epic Code:LAB3512Epic Name:Glucose Tolerance Gest STD 100 GM 3 HR
Order Instructions:GTTG includes GLUF, GLU1, GLU2, GLU3
Synonyms:Glu OB; Glucose 3 Hour; GTT; Glucose Challenge; GTTG; GLC; Gestational Glucose
Methodology:Bichromatic end point, glucose oxidase
Test Includes:Fasting, 1 hr, 2 hr, 3 hr blood glucose. Standard dose is 100 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:
  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, Fairview Range - FRMC, UMMC-East Bank, Oxboro Bloom, Fairview Lakes - FLMC, Fairview Ridges - FRH, Fairview Northland - FNMC, Fairview Southdale - FSH, UMMC/UMMCH-West Bank)


Reference Range:
Fasting Less than 95 mg/dL
1 hour Less than 180 mg/dL
2 hour Less than 155 mg/dL
3 hour Less than 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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