Is a postpartum (after pregnancy) woman, approximately three months postpartum with a history of possible gestational diabetes mellitus (GDM), diagnosed with diabetes mellitus based on a glucose tolerance test result of 138 mg/dL at two hours?

No, a 2-hour glucose value of 138 mg/dL at three months postpartum does NOT meet diagnostic criteria for diabetes mellitus

This result indicates impaired glucose tolerance (prediabetes), not diabetes. The patient requires immediate intervention with lifestyle modification and/or metformin, plus lifelong diabetes screening.

Diagnostic Criteria for Postpartum Testing

When evaluating women with prior gestational diabetes at 4-12 weeks postpartum (or later, as in this case at 3 months), you must use non-pregnant diagnostic criteria 1, 2:

For diabetes diagnosis using the 75g OGTT:

• Fasting plasma glucose ≥126 mg/dL, OR
• 2-hour plasma glucose ≥200 mg/dL 1, 2

For impaired glucose tolerance (prediabetes):

• 2-hour glucose 140-199 mg/dL 1, 2

This patient's 2-hour value of 138 mg/dL falls below the threshold for both diabetes (≥200 mg/dL) and impaired glucose tolerance (≥140 mg/dL), technically representing normal glucose tolerance by strict criteria. However, values in the 138-139 mg/dL range warrant close monitoring given the patient's GDM history 2.

Critical Distinction: Pregnancy vs. Postpartum Criteria

Common pitfall: Do not apply gestational diabetes diagnostic thresholds (2-hour ≥153 mg/dL) to postpartum testing 1, 3. The cutoffs are completely different:

• During pregnancy (GDM diagnosis): 2-hour ≥153 mg/dL 1, 3
• Postpartum (diabetes diagnosis): 2-hour ≥200 mg/dL 1, 2

Why the 75g OGTT is Mandatory Postpartum

The American Diabetes Association specifically mandates the 75g OGTT over HbA1c testing at 4-12 weeks postpartum because 2, 4:

• Increased red blood cell turnover during pregnancy artificially lowers HbA1c values 2, 4
• Blood loss at delivery further distorts HbA1c results 2, 4
• OGTT is more sensitive for detecting both prediabetes and diabetes in the early postpartum period 2, 4

Immediate Management for This Patient

Even with a technically normal result, this patient requires aggressive intervention given her GDM history 2:

1. Intensive lifestyle intervention targeting weight management, Mediterranean-style diet, and moderate physical activity—this reduces diabetes risk by 72% 2

2. Consider metformin therapy, which reduces progression to diabetes by 40% over 10 years in women with prior GDM and any degree of glucose intolerance 2

3. Establish lifelong screening every 1-3 years using 75g OGTT, fasting plasma glucose, or HbA1c 1, 2, 4

Risk Context

Women with prior GDM have a 50-60% lifetime risk of developing type 2 diabetes, with risk increasing linearly: approximately 20% at 10 years, 30% at 20 years, and 50% at 40 years 2, 4. This patient's borderline result places her at particularly high risk and demands proactive management 2.

Key action point: Even though this specific value doesn't meet diabetes criteria, treat this as a critical warning sign requiring immediate preventive intervention, not reassurance 2.