Gestational Diabetes Screen (ACOG Recommendations)

CPT: 82950
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  • Glucose Tolerance, Gestational Diabetes (One-hour)

Test Includes

50-gram one-hour glucose tolerance challenge

Special Instructions

The patient need not be fasting. The one-hour screen requires a 50-gram oral glucose load or 50-gram "Fresh Test" product ( followed by a plasma glucose determination one hour later. (Refer to Additional Information below.) See the online Endocrine Appendix: Glucose Tolerance: Gestational Diabetes Mellitus for further information regarding glucose tolerance testing.

Expected Turnaround Time

Within 1 day

Related Documents

Specimen Requirements


Serum or plasma


1 mL serum or plasma each tube

Minimum Volume

0.5 mL serum or plasma each tube


Gel-barrier tube or gray-top (sodium fluoride/potassium oxalate plasma) tube


Note: A fasting blood sample is not required. Draw one hour specimen after a 50-gram glucose challenge. The patient should remain seated and not smoke throughout the test. Submit 1 mL serum or plasma for one-hour specimen. Separate serum or plasma from cells within 45 minutes of venipuncture. Gray-top tubes only, may be submitted without centrifugation. Label tube with patient's name and collection time interval (i.e., one-hour).

Storage Instructions

Maintain specimen at room temperature.1

Stability Requirements



Room temperature

14 days


14 days


14 days

Freeze/thaw cycles

Stable x3

Patient Preparation

None; glucose challenge is administered without regard to time of day or time of last meal.

Causes for Rejection

Frozen gray-top tube (frozen plasma from gray-top is acceptable); stressed patient (surgery, infection, corticosteroids) should not have GTT; specimen not labeled with collection time intervals (i.e., one hour)

Test Details


Screening test for gestational diabetes




Patient with known history of diabetes mellitus

Reference Interval

70−139 mg/dL

Critical Value

<40 mg/dL or >500 mg/dL

Additional Information

The American College of Obstetricians and Gynecologists (ACOG) recommends that all pregnant women be screened for gestational diabetes mellitus (GDM)—whether by patient history, clinical risk factors, or with a 50-gram, one-hour loading test at 24 to 28 weeks of gestation to determine blood glucose levels—and suggests relying on the result of the 100-gram, three-hour oral glucose tolerance test for diagnosis (often referred to as a "two-step" method).2

The American Diabetes Association (ADA)3 released standards that vary from the ACOG recommendations. The ADA recommends a simplified "one-step" approach to the screen and diagnosis of gestational diabetes mellitus with a 75-gram, two-hour glucose tolerance test. The LabCorp test according to the ADA recommendations is Gestational Glucose Tolerance Screening and Diagnostics Test (Two-hour, ADA Recommendations) [101000]. A glucose tolerance screen glucose threshold >139 mg/dL after a 50-gram load identifies approximately 80% of women with gestational diabetes mellitus, while the sensitivity is further increased to approximately 90% by a threshold >129 mg/dL. Perform a diagnostic 100-gram oral glucose tolerance test (102004) on a separate day on women who exceed the chosen threshold on 50-gram screening.


1. Labcorp internal studies.
2. American College of Obstetricians and Gynecologists. Committee on Practice Bulletins—Obstetrics. Practice Bulletin No. 137: Gestational diabetes mellitus. Obstet Gynecol. 2013 Aug;122(2 Pt 1):406-416.23969827
3. American Diabetes Association. Standards of Medical Care in Diabetes—2015: Summary of revisions. Diabetes Care. 2015 Jan;38(Suppl 1):S4.25537706


Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
102277 Gest. Diabetes 1-Hr Screen 1504-0 102285 Gestational Diabetes Screen mg/dL 1504-0

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