How is a glucose challenge test (GCT) performed in the diagnosis of gestational diabetes mellitus (GDM)?

Updated: Apr 29, 2020
  • Author: Thomas R Moore, MD; Chief Editor: George T Griffing, MD  more...
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Whether administered at 12 or 26 weeks’ gestation, the GCT can be performed without regard to recent food intake (ie, nonfasting state). Indeed, results from tests performed in fasting subjects are more likely to be falsely elevated than results from tests conducted between meals. [63]

In a systematic review performed for the US Preventive Services Task Force, Donovan and colleagues found that by 24 weeks’ gestation, the 50-g oral GCT and FPG level (at a threshold of 85 mg/dL) are effective for ruling out the presence of gestational diabetes mellitus in pregnant women and that the oral GCT is better for confirming its presence. [66, 67]

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