Oral Glucose Suppression Test

Oral Glucose Suppression Test (Outpatient Only), Glucose, Growth Hormone, OGST

Test Codes

EPIC: LAB1231566

Department

Chemistry

Instructions

• This test must be scheduled through the Beaumont Health Appointment Center at 800-328-8542.

  Patient Preparation

• The patient must be fasting at least 10-12 hours prior to the test. Do not chew gum, smoke, eat or drink (except for small amounts of water) 12 hours prior to the test.
• A physician’s order is required to perform testing. If the appointment is for a small child, the parent should bring a bottle or sippy cup.

Specimen Collection Criteria

1.     Prior to Glucose Administration (fasting specimen):

• Collect: One Gray-top Potassium Oxalate/Sodium Fluoride tube (for Glucose) ) AND one Gold-top SST tube (for Growth Hormone and IGF-1).
• Also acceptable: Two Gold-top SST tubes*.

2.     Administer Glucose Dose: 75 grams of glucose orally over 5 minutes. Please refer to the
       Pediatric Dosage Chart for patients under 18 years of age.

3.     After Glucose Administration (timed specimens):

• Collect: One Gray-top Potassium Oxalate/Sodium Fluoride tube (for Glucose) ) AND one Gold-top SST tube (for Growth Hormone and IGF-1) at 30 minutes, 60 minutes, 90 minutes, and 120 minutes after administration of glucose.
• Also acceptable: Two Gold-top SST tubes* at 30 minutes, 60 minutes, 90 minutes, and 120 minutes after administration of glucose.
• *NOTE: For Glucose testing, all specimens must be collected with the same tube type.  SST tubes must be centrifuged within one hour of collection.
• Record the exact time of collection on the tube. Also specify fasting, 30 minutes, 60 minutes, 90 minutes or 120 minutes on the tube.

Physician Office/Draw Specimen Preparation

• Maintain Gray-top tubes refrigerated (2-8°C or 36-46°F) prior to courier transport. (Minimum: 0.5 mL)
• Let SST specimens clot 30-60 minutes then centrifuge to separate serum from cells.
  • For Glucose specimens, refrigerate (2-8°C or 36-46°F) the centrifuged SST within two hours of collection. (Minimum: 0.5 mL per specimen)
  • For Growth Hormone specimens, transfer serum to a plastic transport tube and freeze (-20°C/-4°F or below) immediately. (Minimum: 1.0 mL per specimen)

Preparation for Courier Transport

Transport:

• For Growth Hormone serum, refrigerated (2-8°C or 36-46°F). (Minimum: 1.0 mL per specimen)
• For Glucose, Gray-top tube or centrifuged SST tube refrigerated (2-8°C or 36-46°F). (Minimum: 0.5 mL per specimen)

Rejection Criteria

• Hemolyzed specimens.
• Specimens in tubes containing EDTA.
• Specimens in non-sterile or leaking containers.
• Specimens not collected or processed as indicated.

In-Lab Processing

Samples must be prepared as stated above. Let SST specimens clot 30-60 minutes. Centrifuge SST, Gray-top tubes, or Microtainers® to separate serum or plasma from cells. Serum specimens for Growth Hormone must arrive frozen. Deliver immediately to the appropriate testing station.

Storage

Specimen Stability for Testing:

Growth Hormone

Centrifuged SST Tubes and Microtainers® with Separator Gels
Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): Unacceptable

Red-top Tubes and Microtainers® without Separator Gels
Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): Unacceptable

Serum Specimens (Pour-Overs)
Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): 8 hours
Frozen (-20°C/-4°F or below): 2 months

Glucose

Centrifuged SST Tubes and Microtainers® with Separator Gel
Room Temperature (20-26°C or 68-78.8°F): 4 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): Unacceptable

Gray-top Tubes
Room Temperature (20-26°C or 68-78.8°F): 24 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): Unacceptable

Serum Specimens (Pour-Overs)
Room Temperature (20-26°C or 68-78.8°F): 4 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): 7 days

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 5 days

Laboratory

Glucose
Dearborn Chemistry Laboratory
Grosse Pointe Chemistry Laboratory
Royal Oak Automated Chemistry Laboratory
Troy Chemistry Laboratory

Performed

Growth Hormone
Monday – Friday. Results available within 2 business days.

Glucose
Sunday – Saturday, 24 hours a day.
Results available within 24 hours of receipt in the Laboratory.

Reference Range

Growth Hormone

Adult Males: 0.1-3.0 ng/mL.
Adult Females: 0.1-8.0 ng/mL.
Reference range not established for children less than 19 years of age.

In normal individuals, acromegaly is ruled out if the patient’s Growth Hormone level is less than 1.0 ng/mL at any point in the timed sequence. False positive results can occur in patients with diabetes mellitus, anorexia, liver failure, tall adolescents, and individuals with growth hormone resistance.

Glucose
Fasting: 60-99 mg/dL.
30 Minutes. 50-199 mg/dL.
60 Minutes: 50-199 mg/dL.
90 Minutes: Reference range has not been established.
120 Minutes: 50-139 mg/dL.

Test Methodology

Chemiluminescent Immunoassay, Enzymatic.

Interpretation

In normal individuals, acromegaly is ruled out if the patients GH level is less than 1.0 ng/mL at any point in the timed sequence. False positive results can occur in patients with diabetes mellitus, anorexia, liver failure, tall adolescents, and individuals with growth hormone resistance disorders.

Clinical Utility

For the diagnosis of Acromegaly and to determine status of remission after pituitary surgery.

CPT Codes

80430, 83003, 84035, 82947x2.

Contacts

Last Updated

10/16/2025