2-hour OGTT glucose optimal range and reference range
Compiled by Alina Radu, founder of Sera, from the published sources below · Last reviewed November 9, 2026
Sera's bands for 2-hour OGTT glucose:
- Optimal 70 – 120 mg/dL (3.9 – 6.7 mmol/L); sufficient 70 – 140 mg/dL (3.9 – 7.8 mmol/L); out of range below 70 or above 140 mg/dL.
Evidence grade: Established clinical threshold. A band edge that corresponds to a recognised diagnostic, risk or treatment threshold from a major clinical guideline or public-health body.
All units
| Unit | Optimal | Sufficient | Out of range |
|---|---|---|---|
| mg/dL | 70 – 120 | 70 – 140 | below 70 or above 140 |
| mmol/L | 3.9 – 6.7 | 3.9 – 7.8 | below 3.9 or above 7.8 |
What the evidence says
Bands follow the standardised 75 g OGTT thresholds in the ADA Standards of Care 2026: impaired glucose tolerance from 7.8 mmol/L (140 mg/dL), diabetes from 11.1 mmol/L (200 mg/dL). Diagnostic because the glucose load is standardised, unlike a post-meal sample. The optimal band ending at 6.7 mmol/L (120 mg/dL) is a functional target: no guideline defines a tighter 2-hour target below 7.8, although risk rises gradually through the normal range rather than starting at the threshold. A 2-hour result below 3.9 mmol/L (70 mg/dL) is flagged as low, as it is for fasting glucose.
Sources
- Diagnosis and Classification of Diabetes: Standards of Care in Diabetes—2026 — American Diabetes Association Professional Practice Committee — Diabetes Care, 2026 · Clinical guidelineTable 2.2 defines impaired glucose tolerance as a 2-hour value of 140 to 199 mg/dL (7.8 to 11.0 mmol/L) during a 75 g OGTT; Table 2.1 defines diabetes as 200 mg/dL (11.1 mmol/L) or more. Sera's acceptable band stops just below 140 mg/dL.
- Low Blood Sugar (Hypoglycemia) — Centers for Disease Control and Prevention, 2024 · Government / public-health guidanceBlood sugar below 70 mg/dL (3.9 mmol/L) is called low blood sugar, whenever it is measured. The page is written for people with diabetes; it is the conventional figure behind the lower edge of this band.
What Glucose (2h OGTT) measures
The 2-hour blood sugar from a formal oral glucose tolerance test, where you drink a standard 75g glucose solution after fasting.
Because the glucose load is standardised, this one is diagnostic rather than indicative. Under 7.8 mmol/L (140 mg/dL) is a normal response, 7.8 to 11.0 is impaired glucose tolerance, and 11.1 or above is in the diabetes range. Large cohort studies find the 2-hour value predicts long-term risk better than fasting glucose does.
Related blood sugar markers
- Fasting Glucose
- Glucose (Random / Non-Fasting)
- Fasting Insulin
- HbA1c (Glycated Hemoglobin)
- Glucose (2h Post-Meal)
- Fructosamine
- 1,5-Anhydroglucitol (1,5-AG)
See 2-hour OGTT glucose in the full list of biomarker ranges