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Test Code GTT2HR Glucose, Tolerance, 2 Hours (GTT)

Performing Location

Southwestern Vermont Medical Center

Specimen Collection Information

Specimen  Min. Test Volume Collection Container Special Handling
Blood 0.1 mL Gold top
Marble Red top		  

Reference Ranges & Critical Values

Assay Gender Age Range Normal Range Critical Values Units
GTT2HR ALL 0 Minutes – 150 Years   <45
>500		 mg/dL

Collection Instructions

Refer to Glucose Tolerance Protocols for additional instructions.

  1. Confirm that the patient has fasted 10-16 hours.

  2. Collect urine sample and run dipstick urine test. If test is positive, consult physician to determine whether to continue with tolerance test.

  3. Draw fasting blood sample.

  4. Have patient drink 225 mL (7.5oz) Dextol Glucose Tolerance Beverage for a dose of 75 grams of glucose. See dosage chart if patient is less than 91 lbs. Record time.

  5. Patient should be instructed to remain seated, continue fasting (except water) and not to smoke during the test. Ask the patient to notify staff if he/she should feel ill.

  6. Draw blood sample at 2.0 hours from the time the Dextol was given.

Interpretive Data

Fasting* Glucose Interpretive Criteria:

  • Normal: 65 - 99 mg/dL
  • Impaired Fasting Glucose: 100 - 125 mg/dL
  • Consistent with Diabetes Mellitus**: ≤126 mg/dL

*Fasting is defined as no caloric intake for at least 8 hours.

**In the absence of unequivocal hyperglycemia, a plasma glucose value ≥ 126 mg/dL should be repeated on a subsequent day. 

 

2.0 Hour Glucose Tolerance Interpretive Criteria

  • Normal: 70 - 139 mg/dL
  • Impaired Glucose Tolerance: 140 - 199 mg/dL
  • Possible Diabetes: > 199 mg/dL

Diagnosis and Classification of Diabetes Mellitus Position Statement from the American Diabetes Association. Diabetes Care Volume 33 Supplement 1 Jan 2010.

Day(s) Performed

Monday - Saturday

CPT

82950

LOINC

1518-0