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Test Code Billings Clinic: 4101 Glucose Tolerance Test (GTT), 3 Hour, Plasma or Serum

Performing Laboratory

Billings Clinic Laboratory: Chemistry

Useful For

  • Screen for type 2 diabetes
  • Diagnose gestational diabetes

Methodology

Hexokinase

Specimen Requirements

Consult Billings Clinic Laboratory at 866-232-2522 for pediatric doses.

 

Serum or plasma should be physically separated from cells as soon as possible with a maximum limit of two hours from the time of collection.

 

  1. Draw blood in a green-top (lithium heparin) tube(s) or a red-top tube (serum) from a fasting patient.
  2. Have adult patient drink entire glucose tolerance beverage supplied. Ingestion should be completed within 10 minutes. The timing starts at this point.
  3. Draw specimens as above at 30 minutes, 1 hour, 2 hours, and 3 hours after ingestion of dose.
  4. During time of draw, patient must not eat or drink with the Exception of plain water.
  5. They may be given ice chips or plain water to moisten mouth.
  6. Spin down each specimen, separate plasma or serum from cells as soon as possible after draw, and send 1 mL of heparinized plasma or serum.
  • It is suggested that patient follow a special high carbohydrate (150-300 g) diet for 3 days prior to this test unless otherwise directed by the physician.
  • Glucose solution will not be given to patients with fasting glucose = 150 mg/dL without notification and consent of physician.
  • Vomiting negates test.
  • Label specimens appropriately (timed interval).

 

DO NOT FREEZE

Storage/Stability

Specimen Type Temperature Time
Plasma, Serum Refrigerated 3 days
  Ambient 8 hours

Reject Due To

  • Specimens received frozen
  • Gross hemolysis

Reference Values

Varies

Day(s) Test Set Up

Daily

Test Classification and CPT Coding

82951 - Glucose; quantitative,tolerance test (GTT), 3 specimens (includes glucose)
82952 x 2 - Glucose; quantitative,tolerance test, additional specimens

LOINC Code Information

Reporting Name LOINC Code
Glucose, Fasting 2345-7
GTT, 30 min, 1 hr, 2 hr, 3 hr 2345-7