Blood Glucose Classifier (SBD)

Blood glucose classification: fasting, OGTT and HbA1c

Diabetes mellitus (DM) is diagnosed by three complementary laboratory criteria. Using the Brazilian Diabetes Society (SBD 2023) thresholds, aligned with the American Diabetes Association (ADA): fasting plasma glucose (8h fast) is normal at <100 mg/dL, impaired fasting glucose (IFG) at 100–125 mg/dL, and diabetes at ≥126 mg/dL (confirmed on a second sample).

The 75 g oral glucose tolerance test (OGTT), measured 2 hours post-load, classifies as normal at <140 mg/dL, impaired glucose tolerance (IGT) at 140–199 mg/dL, and diabetes at ≥200 mg/dL. Glycated hemoglobin (HbA1c) reflects mean glycemia over the prior ~3 months: normal <5.7%, prediabetes 5.7–6.4%, diabetes ≥6.5% (assay aligned with DCCT/NGSP).

Applications

Screening of adults ≥35 years or earlier when risk factors are present (obesity, family history, gestational DM, PCOS, dyslipidemia, hypertension); monitoring of prediabetes and lifestyle response; classification supporting clinical decisions about metformin, GLP‑1 agonists or insulin. The three tests are not interchangeable and may give discordant results — ADA recommends repeating the same test for confirmation when feasible.

FAQ

Why can HbA1c be misleading? Hemoglobinopathies, iron-deficiency anemia, recent transfusion, chronic kidney disease and hemolysis distort A1c. In these cases prefer fasting glucose or OGTT.

Is one abnormal result enough? No. Outside acute hyperglycemic symptoms with random glucose ≥200 mg/dL, the diagnosis requires confirmation on a second day with the same or different test.

Does this tool replace a doctor? No. It is an educational reference based on SBD/ADA cutoffs and does not substitute clinical evaluation, exam ordering or treatment by a qualified professional.