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Glucose Tolerance Test (3 Hr/100 g) (Gestational)

Important Note

Patient must be fasting for 8 - 14 hours prior to first specimen collection.

Additional Codes

Epic# -

LAB5713

 

Cerner name(s):

  • GTT 100 gram 3 hr gestational diag or Glucose tolerance testing 100 gram 3 hr gestational diag.

Performing Lab(s)

Memorial-Belleville & Memorial-Shiloh

Specimen Requirement (s)

Specimen Type: plasma (preferred) or serum

Container/Tube:   mint green LiHep tube, SST (gold or marble), plain red top, lavender (EDTA) tube

Specimen Volume:    full tube

Specimen Minimum Volume: 1 mL of plasma

 

Collection Instructions:

  1. Draw fasting specimen.
  2. Give patient 100 g glucose tolerance beverage (or acceptable substitute as determined by lab or physician)
  3. Draw 2nd specimen at 1 hour post consumption of beverage.
  4. Draw 3rd specimen at 2 hours post consumption of beverage.
  5. Draw 4th specimen at 3 hours post consumption of beverage.

Unacceptable Conditions

Avoid hemolysis. 

Day(s)/Shift(s) Test Set Up and Turnaround Time

Sunday through Saturday

Hours: 24 hours

 

Turnaround Time:

STAT: No

Routine: less than 8 hours from receipt.

Transport and Stability

Transport temperature: Ambient to lab

Reference Values

Fasting (3H/100g)

Reference Values

Critical Low

Critical High

< 94 mg/dL

≤ 54 mg/dL

≥ 450 mg/dL

 

1 Hour (3H/100g)

Reference Values

Critical Low

Critical High

< 179 mg/dL

≤ 54 mg/dL

≥ 450 mg/dL

2 Hours (3H/100g)

Reference Values

Critical Low

Critical High

< 154 mg/dL

≤ 54 mg/dL

≥ 450 mg/dL

3 Hours (3H/100g)

Reference Values

Critical Low

Critical High

< 139 mg/dL

≤ 54 mg/dL

≥ 450 mg/dL

Interpretive Data

Interpretive data

100 gram 3 hour Gestational Diabetes Diagnostic

Diagnostic criteria require that 2 or more of the following criteria be met:

Fasting: < to 95 mg/dL

1 hour: ≥ to 180 mg/dL

2 hour: ≥ to 155 mg/dL

3 hour: ≥ to 140 mg/dL

Reference Interval Info:

Harper, L.M.,et al. Carpenter- Coustan Compared with National Diabetes Data Group Criteria for Diagnosing Gestational Diabetes. Obstetrics and Gynecology 2016:127 (5): 893-898.

Diabetes Care 2020; 43(Suppl 1):S14-31

Current interpretive data was last revised 2/17/2021.