Normal 1-Hour Glucose Value After 75g OGTT in Non-Pregnant Individuals
There is no formally established "normal" 1-hour glucose threshold for non-pregnant individuals in standard diabetes diagnostic criteria, as the 1-hour measurement is not routinely used outside of pregnancy. 1
Standard Diagnostic Approach for Non-Pregnant Adults
The 75g OGTT in non-pregnant individuals relies on only fasting and 2-hour measurements for diabetes diagnosis, not the 1-hour value. 2
Established diagnostic criteria include:
- Fasting glucose ≥126 mg/dL (7.0 mmol/L) indicates diabetes 2
- 2-hour glucose ≥200 mg/dL (11.1 mmol/L) indicates diabetes 2
- 2-hour glucose 140-199 mg/dL (7.8-11.0 mmol/L) indicates impaired glucose tolerance 2
Emerging Evidence for 1-Hour Measurement
While not part of standard diagnostic criteria, research suggests that a 1-hour glucose <155 mg/dL may represent normal glucose metabolism in non-pregnant adults. 3, 4
Key research findings:
- 1-hour glucose ≥155 mg/dL (8.6 mmol/L) identifies individuals with impaired β-cell function, insulin resistance, and increased cardiovascular risk even when fasting and 2-hour values remain normal 3, 4
- Among subjects with normal glucose tolerance by standard criteria, those with 1-hour glucose >155 mg/dL had significantly worse metabolic profiles including higher insulin resistance, impaired β-cell function, elevated blood pressure, and adverse lipid profiles compared to those with 1-hour glucose ≤155 mg/dL 4
- 1-hour glucose ≥155 mg/dL predicts future diabetes progression better than HbA1c or 2-hour glucose values alone in multiple populations 3
Clinical Context: Pregnancy vs. Non-Pregnancy
The 180 mg/dL threshold used in pregnancy should not be applied to non-pregnant individuals. 2, 1
- In pregnancy, 1-hour glucose ≥180 mg/dL diagnoses gestational diabetes using the one-step approach 2, 1
- This pregnancy-specific threshold was derived from the HAPO study examining pregnancy outcomes, not future diabetes risk in non-pregnant populations 2
- Japanese research identified 179 mg/dL as the upper limit of normal for 1-hour glucose in their population, with values ≥179 mg/dL associated with 26.9% diabetes prevalence 5
Practical Clinical Recommendation
For non-pregnant adults undergoing 75g OGTT, focus on the standard fasting and 2-hour measurements for diagnosis. 2, 1
However, if 1-hour glucose is measured:
- Values <155 mg/dL suggest normal glucose metabolism 3, 4
- Values ≥155 mg/dL warrant closer monitoring even with normal fasting and 2-hour values, as these individuals have significantly increased risk for diabetes progression and cardiovascular disease 3, 4
- Consider more aggressive lifestyle intervention and shorter screening intervals for those with 1-hour glucose ≥155 mg/dL 3
Important Caveats
The 1-hour measurement provides additional prognostic information beyond standard diagnostic criteria, identifying high-risk individuals who would otherwise be classified as having normal glucose tolerance. 1, 3
Current guidelines do not require 1-hour measurement in non-pregnant adults, so most laboratories performing standard 75g OGTT will only report fasting and 2-hour values unless specifically requested. 2, 1