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Test Code LAB4325 GTT, FASTING

Important Note

Plasma or serum samples without preservative (Sodium Floride Grey top tube)  should be separated fromteh cells or clot within half and hour of being drawn. When blood is drawn and permitted to clot and stand uncentrifuged at room temperature the average decrease in serum glucose is ~7% in 1 hour.

Specimen Type

Preferred Specimen: Lithium Heparin Plasma (Mint Green Top, Dark Green Top)
Alternative Specimen: Serum (SST, Gold, Corvac, Tiger, Red Top Tube) Sodium Flouride/Potassium Oxilate(Gray Top Tube)

Specimen Volume

1 mL

Minimum Volume

0.5 mL

Turnaround Time

STAT: 1 hour
Routine: 4 hours

Test Schedule

Daily

Sample Stability

Serum/ Plasma

  • Room Tempurature: 8 hours
  • Refrigerated: 3 days

Grey Top (Sodium Floride)

  • Room Tempuratue: 3 days
  • Refrigerated: 3 days

Method

Hexokinase

Reference Ranges

Glucose mg/dL

0-2 days 40-90

2 days-1 mo 60-105

Adult 65-99 Pregnant 65-94

ADA Diagnostic Categories for nonpregnant adults:

Impaired fasting glucose 110-125 mg/dL A fasting glucose result of 126 mg/dL or greater indicates diabetes if the abnormality is confirmed on a subsequent day.

A random glucose result of GT 200 mg/dL indicates diabetes if the abnormality is confirmed on a subsequent day.

Test Components

Glucose, mg/dL.

CPT Codes

82947