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Epic Code LAB1230278 Glucose Tolerance, 2 hour test, 75g (Gestational Diabetes)

Important Note

  • For outpatient collection: Providers please instruct patient to arrive at least 3 hours prior to the lab closing to ensure there is enough time to complete the test.
  • This test is recommended and only available for PREGNANT patients.
  • Fasting specimen required -  A fasting glucose specimen will be drawn.

Test Name Alias

Oral Glucose| GTT | OGTT | 123002002

Interface Order Alias

1230278

Ordering Instructions

This test is recommended as a follow-up or confirmatory test for an abnormal One Hour Post (50 gram) OGTT.

 

This test is recommended and only available for PREGNANT patients.

 

For safety and accuracy of testing, patients are encouraged to have Oral Glucose Tolerance Tests (OGTT) performed at one of our Outpatient Service Centers.

Collection Instructions

  • A fasting glucose specimen will be drawn.
  • The patient is given a 75 gram oral glucose load.
  • Another specimen is drawn 1 hour and then 2 hours later.
  • GlucoCrushTM, the glucola drink used in Spectrum Health Grand Rapids Laboratory does not contain gluten.

 

Specimen Collection: Blood

 

Container(s): Gray Top (Potassium Oxalate and Sodium Fluoride)

  • Also acceptable: Light Green Top (Lithium Heparin Gel) OR 5.0 mL Gold Top (Serum Separator-SST Gel)
  • Minimum Volume to Collect: 1.0 mL
  • Neonate Volume to Collect: 0.5 mL
  • Capillary collect ok? Yes
  • Microtainer acceptable: Yes

Collection Instructions:

  • Fasting specimen required
  • After collection, gently invert tube 8-10 times.
  • Gray top whole blood is preferred specimen type
  • If collecting green or gold top:
    • Specimen should be processed within 2 hours – See Processing Instructions.
    • Processed Specimen: Plasma or Serum
    • Centrifuge/Spin: Yes
    • Aliquot: Yes
    • Processing Instructions:
      • Gold Tube/Serum: Allow blood to clot for 30 minutes in a vertical position and centrifuge within 2 hours.
      • Green Tube/Plasma: Centrifuge after collection.
      • Minimum plasma/serum volume: 0.5 mL

Transport Temperature: Refrigerated

 

Lab Central Instructions:

  • Centrifuge Gray-top tubes before delivery to the appropriate testing station.

Specimen Stability

Ambient: 8 hours

Refrigerate: 72 hours

Frozen: aliquot plasma/serum for longer storage

Laboratory Retention: 72 hours

Test Frequency

Available daily, usual TAT 1 day.

Reference Range

Glucose Fasting: 70-99 mg/dL

Glucose 1 Hour Post 75g: ≤180 mg/dL

Glucose 2 Hour Post 75g: 50-139 mg/dL

Performing Department

Chemistry

Performing Department Laboratory Location

CHW: Corewell Health Reference Laboratory, Grand Rapids, MI
CHS: Corewell Health Lakeland St. Joseph Laboratory, St. Joseph, MI

Methodology

Enzymatic

CPT

82951

CDM Code

3018295101

Epic Test ID

123002002

LOINC

Currently not available

Reviewed Date

3/7/2024

Updated Date

5/13/2025 CHS info added

Orderable Regions

Southwest; West