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Test Code GTT3HR Glucose, Tolerance, 3 Hours, Pregnancy (GTT)

Performing Location

Southwestern Vermont Medical Center

Specimen Collection Information

 Specimen  Min. Test Volume Collection Container Special Handling
Blood 0.1 mL Light Green (lith. heparin) top
Gold top
Marble Red top		  

Reference Ranges & Critical Values

Assay Gender Age Range Normal Range Critical Values Units
GTT3HR ALL 0 Minutes – 150 Years  

< 45

> 500

 mg/dL

Interpretive Data

Criteria for diagnosis of gestational Diabetes Mellitus: Any two patient levels above the following cutoff levels (100g challenge):

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

Collection Instructions

Refer to Standard Glucose Tolerance Protocols.

  1. Confirm that 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 a tolerance test.

  3. Draw fasting blood sample.

  4. Have patient drink 300mL (10oz) of Dextol Glucose Tolerance Beverage for a dose of 100 grams of glucose. Record time.

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

  6. Draw blood samples at 1, 2 and 3 hours from the time the Dextol was given.

Specimen Stability

3 days at 2-8°C

Day(s) Performed

Monday - Sunday

LOINC

50608-9

CPT

82951