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Epic Code LAB1230102 Glucose Tolerance, 2 hour test, 75g (Non-Gestational)

Important Note

  • This test is recommended and only available for non=pregnant patients.
  • Fasting specimen required -  A fasting glucose specimen will be drawn.

Test Name Alias

Glucose tolerance 2 hr Test (Lab only) Glucose | 2 hr, Glucose Tolerance | Glucose | O9221  | GTT | OGTT | 178

Interface Order Alias

1230102

Ordering Instructions

  • This test is recommended and only available for NON-PREGNANT patients.
  • The patient must be fasting for this test. No caloric or caffeine intake for at least 8 hours. Do not drink (other than water), eat, smoke, chew gum, candy, cough drops, etc. for at least 8 hours prior to blood tests.
  • For safety and accuracy of testing, patients are encouraged to have Oral Glucose Tolerance Tests (OGTT) performed at one of our Outpatient Service Centers.
  • GlucoCrushTM, the glucola drink used in Spectrum Health Grand Rapids Laboratory does not contain gluten.

Collection Instructions

  • A fasting glucose specimen will be drawn.
  • The patient is given a 75 gram oral glucose load.
    • Pediatric patients under 95 lbs: Use the following calculation to determine the amount of glucola to be administered: 2.4 x Body weight in lbs = mL of 100g Glucola to administer
  • A second specimen is drawn two hours later.
  • GlucoCrushTM, the glucola drink used in Spectrum Health Grand Rapids Laboratory does not contain gluten.

 

Specimen Collection: Blood

 

Container(s): 4.5 mL Mint Green Top (Lithium Heparin Gel) or 5.0 mL Gold Top (Serum Separator-SST Gel)

  • Preferred Volume to Collect: 4.5 mL
  • 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.
  • Specimen should be processed within 2 hours – See Processing Instructions.

 

Processing Instructions (Laboratory, Outpatient or Off-site collection)

  • Processed Specimen: Plasma or Serum
  • Centrifuge/Spin: Yes
  • Aliquot: Yes
  • Processing Instructions:
    • Plasma is preferred specimen type
    • Green Tube/Plasma: Centrifuge after collection.
    • Gold Tube/Serum: Allow blood to clot for 30 minutes in a vertical position and centrifuge within 2 hours.
    • Minimum plasma/serum volume: 0.5 mL
  • Transport Temperature: Refrigerate

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

  Fasting 2 hour
Normal 70 - 99 mg/dL 65 - 139 mg/dL
Prediabetes 100 - 125 mg/dL 140 - 199 mg/dL
Diabetes ≥126 mg/dL ≥ 200 mg/dL

 

Diagnosis of diabetes requires 2 abnormal test results from the same sample type or in 2 separate test samples.

Classification and Diagnosis of Diabetes: Standards of Medical Care in Diabetes - 2021. Diabetes Care Jan; 44(Supplement 1):S15-S33.  https://doi.org/10.2337/dc21-S002 

Performing Department

Chemistry

Performing Department Laboratory Location

Corewell Health Reference Laboratory, Grand Rapids, MI

Methodology

Enzymatic

CPT

82951, 82947

CDM Code

3018294701, 3018294701

Epic Test ID

1230100114, 1230100723

LOINC

Currently not available

Reviewed Date

3/7/2024

Updated Date

3/14/2024 - Reference Range