What is the diagnosis for a patient with an oral glucose tolerance test showing fasting plasma glucose 140 mg/dL, 1‑hour glucose 240 mg/dL, and 2‑hour glucose 130.9 mg/dL?

Diagnosis: Diabetes Mellitus

Based on your OGTT results—fasting glucose 140 mg/dL, 1-hour 240 mg/dL, and 2-hour 130.9 mg/dL—you meet diagnostic criteria for diabetes mellitus because your fasting glucose is ≥126 mg/dL. 1

Diagnostic Reasoning

Your OGTT results must be interpreted using standard diabetes diagnostic criteria, not gestational diabetes thresholds:

• Fasting plasma glucose ≥126 mg/dL (7.0 mmol/L) confirms diabetes. Your fasting value of 140 mg/dL exceeds this threshold. 1

• 2-hour plasma glucose ≥200 mg/dL (11.1 mmol/L) also confirms diabetes. Your 2-hour value of 130.9 mg/dL does not meet this criterion—it falls in the normal range (below 140 mg/dL). 1

• The 1-hour glucose value of 240 mg/dL is not used for diabetes diagnosis in non-pregnant adults; only fasting and 2-hour values are diagnostic. 1

Why This Is Diabetes, Not Prediabetes

The distinction is critical:

• Impaired fasting glucose (prediabetes) is defined as fasting glucose 100–125 mg/dL. Your fasting of 140 mg/dL exceeds this range. 1, 2

• Impaired glucose tolerance (prediabetes) is defined as 2-hour glucose 140–199 mg/dL. Your 2-hour value of 130.9 mg/dL is actually normal (below 140 mg/dL), not in the prediabetes range. 1, 3, 2

• Your fasting glucose alone establishes the diagnosis of diabetes; the normal 2-hour value does not negate this. 1

Confirmation Requirements

In the absence of unequivocal hyperglycemia with acute metabolic decompensation or classic symptoms (polyuria, polydipsia, unexplained weight loss), the diagnosis must be confirmed on a separate day using any of the following: 1, 3

• Repeat fasting plasma glucose ≥126 mg/dL 1
• Hemoglobin A1C ≥6.5% 1
• 2-hour OGTT glucose ≥200 mg/dL 1

If you have classic diabetes symptoms (excessive thirst, frequent urination, unexplained weight loss, blurred vision, fatigue), a single abnormal test is sufficient for diagnosis. 1

Common Pitfall to Avoid

Do not misinterpret your 2-hour value of 130.9 mg/dL as "prediabetes" or "impaired glucose tolerance." This value is completely normal. The diagnosis rests on your elevated fasting glucose, which unequivocally indicates diabetes. 1, 3

Next Steps

• Confirm the diagnosis with a repeat fasting glucose or HbA1C on a different day (unless you have symptoms). 1, 3
• Begin evaluation for diabetes complications (retinopathy, nephropathy, neuropathy, cardiovascular disease). 1
• Initiate lifestyle modification (5–7% weight loss, ≥150 minutes/week moderate physical activity) and consider pharmacologic therapy based on your HbA1C and cardiovascular risk profile. 1, 2