Glucose Tolerance, Standard (Non-Pregnant)


Sunquest Code:GTT  
Epic Code:LAB3511Epic Name:Glucose Tolerance STD Non Preg
Order Instructions:GTT includes GLUF and GLU2.
Synonyms:GTT; Oral Glucose Tolerance Test (OGTT)
Methodology:Colorimetric reflectance spectrophotometry; glucose oxidase
CPT Code:82947, 82950
Test Includes:Fasting and 120 min glucose. Adult dose is 75 g glucose. Pediatric dose is 1.75 g glucose/kg of body weight up a maximum dose of 75 g. For pregnancy, refer to Glucose Tolerance, Std. Gestational
Turnaround Time:Performed Mon-Fri, 0700-1700; turnaround time is 2 hours from the time the last specimen was collected.
Special Instructions:The oral glucose tolerance test (OGTT) is not recommended for routine clinical use.
Associated Links:

Glucose Tolerance Testing



Collection Instructions

Specimen:Blood
Optimal Volume:2.5 mL
Minimum\Peds Volume:0.6 mL
Container:Green (lithium heparin, gel) (Green (lithium heparin) on ICE, Green (sodium heparin, no gel), Green (sodium heparin, no gel) on ICE, Gray (sodium fluoride + potassium oxalate), Red (no gel), Red or gold (gel))
Collection Instructions:

 

·      Measure fasting urine or blood glucose level before glucose solution is administered. Abnormal fasting results greater than 126 mg/dL are reported to physician before continuing test.

·      Administer oral glucose solution and begin timing as patient begins to drink glucose solution. Adult loading dosage is 75 g glucose by mouth in at least 300 mL fluid. Pediatric dose is 1.75 g glucose/kg body weight not to exceed 75 g.

·      Collect specimen 2 hours from the time patient finishes drinking the glucose solution. Occasionally, a 1 hour specimen is collected. Label the specimen with collection time, patient name, and identification number.

·      For glucose tolerance blood specimens collected in the hospital, deliver to the laboratory individually as collected. Should not perform on hospitalized patients in stressed state.

 

Patient Preparation:Please do not eat 10-12 hours before your appointment if you are coming in fasting for labs on lipids, cholesterol or glucose (sugar). This does not apply to pregnant women.
Water, hot tea and black coffee (with nothing added) is okay. Do not drink other fluids, diet soda or chew gum.
If you have concerns about taking your medications, please send a message by clicking on Secure Messaging, Message Your Care Team.
Contraindications:If patient becomes ill or vomits, test must be discontinued.


Processing and Shipping

Specimen Processing:Centrifuge and aliquot 1.25 mL, 0.2 mL minimum for each timed specimen collection. Store in refrigerator.
Shipping Instructions:Ship at refrigerated temperature.
Test Performed at or Referral Lab Chemistry  (University of Minnesota Health Maple Grove Clinics, Fairview Range - FRMC, UMMC-East Bank, Oxboro Bloom, Fairview Lakes - FLMC, Fairview Ridges - FRH, Fairview Northland - FNMC, Fairview Southdale - FSH, UMMC/UMMCH-West Bank)


Interpretive

Reference Range:

 

Criteria for Diagnosis of Diabetes Mellitus

1.     Symptoms of diabetes (poluria, polydipsia, and unexplained weight loss) plus a casual (i.e., any time of day without regard to the last meal) plasma/serum glucose level of greater than or equal to 200 mg/dL.

Or

2.     Fasting plasma/serum glucose (FPG) level of greater than or equal to 126 mg/dL after a minimum 8-hour fast.

Or

3.     2-hour post load glucose level of greater than or equal to 200 mg/dL, the oral glucose tolerance test (OGTT) is not recommended.  

 

In the absence of unequivocal hyperglycemia, these criteria should be confirmed by repeat testing on a different day.

 

Pre-diabetes: Impaired Glucose Tolerance (IGT) & Impaired Fasting Glucose (IFG)

Patients with IFG and/or IGT are now referred to as having “pre-diabetes” indicating the relatively high risk for development of diabetes in these patients. In the absence of pregnancy, IFG and IGT are not clinical entities in their own right, but rather, risk factors for the future development of diabetes mellitus and/or cardiovascular disease.

 

Category

Fasting Glucose

mg/dL

2-Hour Postload Glucose

mg/dL

Normal

Less than 100

Less than 140

IFG

100-125

 

IGT

 

140-199

Diabetes

126 or greater

200 or greater

 

 



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