Insulin Response to Glucose (IROGTT)

Cleveland HeartLab I, Test


ABN Requirement: No

CPT Code:
IROGTT, 2 Samples: 83525 (x2)
IROGTT, 3 Samples: 83525 (x3)
Each additional sample: 83525

Order Code:
IROGTT, 3 Samples (Fasting, 1 hour, 2 hour): C559
IROGTT, 2 Samples (Fasting, 1 hour): C558
IROGTT, 2 samples (Fasting, 2 hour): 1344
IROGTT, Additional Insulin 1: 1419
IROGTT, Additional Insulin 2: 1420

Specimen: Serum
Volume:  1.0 mL (per timed specimen)
Minimum Volume:  0.5 mL (per timed specimen)
Container: Gel-barrier tube (SST)

Fasting: Overnight fasting is required.

Patient Preparation:

Overnight fasting is required. High carbohydrate diet for 3 days before test. Patient NPO after midnight; glucose solution 1.75 g/kg body weight (maximum dose 75g) orally administered after collection of the fasting specimen


  1. Draw fasting specimen. Collect 1 mL serum for each timed specimen post glucose dose. All tubes must be clearly labeled with the time of draw. Submit all tubes with one test requisition.
  2. Collect and label sample according to standard protocols.
  3. Gently invert tube 5 times immediately after draw. Do not shake.
  4. Allow blood to clot 30 minutes.
  5. Centrifuge for 10-15 minutes.

Transport: Store serum at 2°C to 8°C after collection and ship the same day per packaging instructions included with the provided shipping box.


Ambient (15-25°C): 24 hours
Refrigerated (2-8°C):
7 days
Frozen (-20°C):
28 days

Causes for Rejection: Specimens other than serum; improper labeling; samples not stored properly; samples older than stability limits; hemolysis; plasma; gross icterus

Methodology: Immunoassay (IA)

Turn Around Time:  1 to 3 days

Reference Range:

Insulin Response to GlucoseReference Range
Fasting2.0-18.4 uIU/mL
30 minutes post glucose6.0-86.0 uIU/mL
60 minutes post glucose8.0-112.0 uIU/mL
90 minutes post glucose5.0-68.0 uIU/mL
120 minutes post glucose5.0-55.0 uIU/mL
150 minutes post glucose3.0-46.0 uIU/mL
180 minutes post glucose3.0-20.0 uIU/mL
240 minutes post glucose<15.0 uIU/mL
300 minutes post glucose<8.0 uIU/mL
These values are provided for general guidance only.

Clinical Significance: The insulin response to glucose infusion is useful in evaluating patients with hypoglycemia and suspected insulin resistance.

The CPT codes provided 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 payer being billed.