A B C D E F G H I J K L M N O P Q R S T U V W X Y Z #

Glucose Tolerance, 3 hour

Test Code
GTT3


Alias/See Also
Epic: LAB164


Preferred Specimen

Specimen Type: Plasma
Collection Container: Grey top (potassium oxalate/sodium fluoride)
Specimen Volume: 3 mL




Patient Preparation
  1. Patient should be fasting for at least eight (8) hours before test and no longer than sixteen (16) hours.  Patient cannot eat or drink during test, but water is permitted before and during the test.
  2. Cigarette smoking will affect results and should be avoided.


Minimum Volume

0.1 mL




Other Acceptable Specimens

Specimen Type: Serum
Collection Container: Serum gel, red top




Instructions
  1. Draw a fasting sample and document collection time on the label.
  2. Administer 100 grams oral glucose solution.  Ingestion should be completed within five (5) minutes.
  3. Draw the second sample one (1) hour after ingestion of oral glucose and document collection time on the label.
  4. Draw the third sample two (2) hours after ingestion of oral glucose and document collection time on the label.
  5. Draw the fourth sample three (3) hours after ingestion of oral glucose and document collection time on the label.
  6. Centrifuge and separate cells within 4 hours of collection (for serum specimens, wait until specimen has clotted completely before centrifuging).


Transport Container
Plastic vial


Specimen Stability

Room temperature: 2 days
Refrigerated: 7 days
Frozen: 1 day




Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)

Unlabeled, mislabeled, wrong tube type, QNS, hemolyzed.




Methodology

Hexokinase / G-6-PDH



Setup Schedule

Daily




Report Available

Same day




Reference Range
See laboratory report


Clinical Significance
Blood glucose determinations are commonly used as an aide in the diagnosis and treatment of diabetes. Elevated glucose levels (hyperglycemia) may also occur with pancreatic neoplasm, hyperthyroidism, and adrenal cortical hyperfunction as well as other disorders. Decreased glucose levels (hypoglycemia) may result from excessive insulin therapy or various liver diseases.


Performing Laboratory

Inova Laboratories

2832 Juniper Street

Fairfax, VA 22031




Last Updated: April 17, 2023
Last Review: N. Wolford, April 17, 2023


The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.