Diabetes Diagnosis & Classification: ADA Standards 2025

Diabetes Diagnosis and Classification: Standards of Care in Diabetes - 2025

• American Diabetes Association (ADA) provides current clinical practice recommendations via Standards of Care
• Components of diabetes care, general treatment objectives/guidelines, and tools to assess care quality are given
• An interprofessional expert committee updates standards annually or more often if necessary
• Readers wanting to comment on the Standards of Care can do so through professional.diabetes.org/SOC

Diabetes Mellitus Overview

• A group of metabolic disorders where glucose is underutilized, and produced in excess due to inadequate gluconeogenesis/glycogenolysis
• Hyperglycemia occurs as a result
• Diagnosis involves demonstrating elevated glucose levels in venous plasma or increased A1C in blood

Diabetes Classification

• Includes type 1, type 2, gestational diabetes, and other specific types from causes such as monogenic diabetes, exocrine pancreatic disorders and high-risk meds
• Diagnostic tests encompass A1C or plasma glucose criteria, with plasma glucose including FPG, 2-h PG level during 75-g OGTT, or random glucose with hyperglycemic symptoms/crisis
• Diagnosis needs confirmatory tests unless there is obvious hyperglycemia like a hyperglycemic crisis

Diagnostic Criteria for Diabetes

• A1C of 6.5% (48 mmol/mol) is diagnostic if NGSP-certified and DCCT assay-standardized
• FPG of 126 mg/dL (7.0 mmol/L) requires no caloric intake for 8 hours minimum
• 2-h PG level of 200 mg/dL (11.1 mmol/L) during OGTT, using WHO guidelines, requires 75-g glucose load
• Plasma glucose of 200 mg/dL (11.1 mmol/L) in individuals with classic hyperglycemic symptoms or hyperglycemic crisis, random measurement taken any time of day without regard to meal time

Considerations for Diagnosis

• Two abnormal results from different tests like A1C and FPG can confirm, or the same test at different times
• FPG (or A1C) generally preferred when screening non-pregnant people because it's easier to administer
• 2-h PG test (OGTT) diagnoses more prediabetes/diabetes than the other two tests; preferred for some conditions (cystic fibrosis-related diabetes)
• If no classic hyperglycemia symptoms, testing should be repeated to confirm
• Glucose tests are affordable and available but may have variations in glucose and require fasting/glucose control
• A mixed diet/pattern (150g carbs minimum) advised for 3 days before OGTT to avoid false positives

Prediabetes Diagnostic Criteria

• A1C 5.7-6.4% (39-47 mmol/mol)
• FPG 100 mg/dL (5.6 mmol/L) - 125 mg/dL (6.9 mmol/L) (IFG)
• 2-h PG during 75-g OGTT 140 mg/dL (7.8 mmol/l) - 199 mg/dL (11.0 mmol/l) (IGT)
• Risk increases across the board including below the lower limits, greatest at the extreme tops

Use of A1C in Diabetes Detection and Diagnosis

• A1C testing should use NGSP-certified method as per the name
• Trazable to Diabetes Control and Complications Trial reference assay
• Point-of-care A1C tests for diabetes detection/diagnosis restricted to FDA-approved devices in CLIA-certified labs run by trained personnel
• Substantial discordance between blood glucose/A1C indicate test problem/interference evaluation
• For conditions with altered A1C-glycemia relationship, use plasma glucose instead
• The test measures glucose attached to hemoglobin over the life of a red blood cell up to 120 days, most heavily weighted towards recent exposure, and clinically meaningful results can be observed in less than 120 days if rapid changes in blood sugar levels occur
• Testing cannot be reliably used for an accurate diagnosis in people with anemia among others where hemoglobin is not normal

Confirming a Diagnosis of Diabetes

• Confirmation of diagnosis with 2 abnormal test results needed unless clear clinical diagnosis

Recommendation for classifying Hyperglycemia correctly

• facilitates personalized management

The Main Four Diabetes Classifications

• Type 1 Diabetes (due to autoimmune B-cell destruction, typically leading to absolute insulin deficiency)
• Type 2 Diabetes (due to progressive insulin secretion loss/inadequate amount in the context of insulin resistance)
• Specific types of diabetes (e.g., monogenic diabetes syndromes chemical-induced)
• Gestational Diabetes Mellitus - GDM (diagnosed in the 2nd/3rd trimester)

Overview of diabetes mellitus, its classification, and diagnosis based on the American Diabetes Association standards of care 2025. Discusses hyperglycemia, diagnosis via glucose levels or A1C, and various types including type 1, type 2, and gestational diabetes.