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Labcorp Oklahoma, Inc.
Test Directory


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Glucose Tolerance (4 Hour) w/o Urine

Order Name GTT 4 HR
Test Number: 2002375
Revision Date 05/20/2021
Test Name Methodology LOINC Code
Glucose Fasting
Hexokinase 1558-6 
Glucose 1 Hour Tolerance
Hexokinase 20438-8 
Glucose 2 Hour Total
Hexokinase 20436-2 
Glucose 3 Hour Tolerance
Hexokinase 20437-0 
Glucose 4 Hour Tolerance
Hexokinase 26541-3 
SPECIMEN REQUIREMENTS
Specimen Specimen Volume (min) Specimen Type Specimen Container Transport Environment
Preferred 1 mL (0.5) Plasma Sodium fluoride (gray top) Refrigerated
Alternate 1 1 mL (0.5) Plasma Lithium Heparin PST (Light Green Top) Refrigerated
Alternate 2 1 mL (0.5) Serum Clot Activator SST Refrigerated
Instructions Fasting overnight and during test; Patient may have water. Draw fasting specimen. +
Adults: Give 75 grams of glucola. Children: Adjusted amount of glucola to be calculated by lab. Call (918) 744-2500.
Stability: Ambient 8 hours, Refrigerated 7 days, Frozen 1 month
Fluoride preserved plasma samples are stable at room temperature for 24 hours
GENERAL INFORMATION
Testing Schedule Daily 
Expected TAT 1-2 days  
Clinical Use There are no established guidelines, reference ranges or criteria, for the evaluation of a three hour or four hour specimen following a four hour glucose challenge. 
Notes For more information on this test, access our "Specialized Tests" section.
CPT Code(s) 82951, 82952x2
Lab Section Chemistry