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Test Code 124 Glucose Tolerance Test, Gestational; 100 Gm Load

Additional Codes


PowerChart: Glucose Tolerance Gestational

MA Cerner: GTT 3 Hr Gestational

Specimen Requirement

0.5 mL serum or plasma is required.

Additional Specimen Collection Information

Collect blood in a lithium heparin, green-top or red-top tube fasting and at specified time intervals after the patient has consumed 100 gm of Trutol. PST and SST (gel tubes) are acceptable. Samples with ≥ 3+ lipemia must be cleared prior to analysis. The serum or plasma must be physically separated from the cells within 2 hours of collection.

  • The test is administered in the morning following a fast of between 8-10 hours. The fasting specimen must be tested and within normal range before Trutol is administered.
  • The patient should have had at least 3 days of unrestricted diet and normal physical activity. Instruct the patient to remain seated or reclined throughout the procedure.
  • The patient may have water to drink but nothing else. Coffee and smoking materials are prohibited.
  • The NIH (National Institute of Health) recommends 3 hours in pregnant subjects, with an additional specimen collected at the first and third hour.
  • A physician can request a longer OGTT (Oral Glucose Tolerance Test) with different dosages and specimen collection intervals. Consult a pathologist when this occurs.

Useful For

Diagnosis of Gestational Diabetes Melitis


Testing is performed Monday through Friday.

Same day turn around time.

CPT Code Information

82951 Chemistry: Glucose Testing Glucose; tolerance test (GTT), 3 specimens (includes glucose)

82952 Chemisty: Glucose Testing Glucose; tolerance test (GTT), each additional beyond 3 specimens (List separately in addition to code for primary procedure)

LOINC Code Information

50608-9 Glucose Tolerance 3 Hours Gestational Panel-Serum Or Plasma

Test Method

MercyOne DBQ:

Timed Endpoint; Beckman DXC880i

Mercy DV and MQMA:

Catalytic Oxidation Electrode; iSTAT

MA East and West:

Enzymatic Colorimetric Method; Roche Cobas 6000

Reference Values

"Gestational diabetes" if 2 or more patient values fall within the following parameters :

  • Fasting: ≥ 95 mg/dL
  • 1 hour: ≥ 180 mg/dL
  • 2 hour: ≥ 155 mg/dL
  • 3 hour: ≥ 140 mg/dL