Which of the following findings are NOT diagnostic for diabetes mellitus: hemoglobin A1c >5.5%, fasting plasma glucose ≥126 mg/dL, random plasma glucose ≥200 mg/dL with classic hyperglycemia symptoms, ketosis, or 2‑hour plasma glucose ≥150 mg/dL after an oral glucose tolerance test?

Which Findings Are NOT Diagnostic for Diabetes Mellitus

The findings that are NOT diagnostic for diabetes mellitus are: (a) HbA1c >5.5%, (d) ketosis, and (e) glucose ≥150 mg/dL 2 hours after the glucose tolerance test.

Established Diagnostic Criteria for Diabetes

The American Diabetes Association has defined four specific criteria for diagnosing diabetes mellitus, and only findings that meet these thresholds are diagnostic 1, 2:

Valid Diagnostic Criteria:

• Fasting plasma glucose ≥126 mg/dL (7.0 mmol/L) after at least 8 hours of fasting is diagnostic 1
• 2-hour plasma glucose ≥200 mg/dL (11.1 mmol/L) during a 75-gram oral glucose tolerance test is diagnostic 1
• HbA1c ≥6.5% measured in an NGSP-certified laboratory is diagnostic 1, 2
• Random plasma glucose ≥200 mg/dL (11.1 mmol/L) with classic symptoms of hyperglycemia (polyuria, polydipsia, unexplained weight loss) is diagnostic 1, 2

Analysis of Each Option

Option (a): HbA1c >5.5% - NOT DIAGNOSTIC

• An HbA1c of 5.5% falls well below the diagnostic threshold of ≥6.5% 1
• HbA1c values of 5.7–6.4% define prediabetes, not diabetes 1, 2
• An HbA1c >5.5% but <5.7% is considered normal 2

Option (b): Fasting glucose ≥126 mg/dL - DIAGNOSTIC

• This meets the established diagnostic criterion for diabetes 1, 2
• Confirmation with repeat testing is required unless unequivocal hyperglycemia is present 1, 3

Option (c): Glucose ≥200 mg/dL in random sample with symptoms - DIAGNOSTIC

• This meets diagnostic criteria when classic hyperglycemia symptoms are present 1
• The key requirement is the presence of classic symptoms (polyuria, polydipsia, weight loss) 2

Option (d): Ketosis - NOT DIAGNOSTIC

• Ketosis is a metabolic state that can occur in diabetic ketoacidosis, but it is not a diagnostic criterion for diabetes mellitus itself 1
• Ketosis can occur in other conditions including starvation, ketogenic diets, and alcoholic ketoacidosis 1
• While diabetic ketoacidosis indicates severe insulin deficiency in someone with diabetes, the presence of ketosis alone does not diagnose diabetes 1

Option (e): Glucose ≥150 mg/dL 2 hours after OGTT - NOT DIAGNOSTIC

• The diagnostic threshold for the 2-hour OGTT is ≥200 mg/dL, not ≥150 mg/dL 1
• A 2-hour value of 140–199 mg/dL defines impaired glucose tolerance (prediabetes), not diabetes 1, 2
• A value of 150 mg/dL falls within the prediabetes range 2

Critical Confirmation Requirements

All diagnostic test results require confirmation with repeat testing unless the patient presents with unequivocal hyperglycemia or hyperglycemic crisis 1, 3:

• The same test should preferably be repeated for confirmation 1, 3
• Two abnormal results from the same sample or separate samples are required 1, 2
• If two different tests both exceed diagnostic thresholds, diabetes is confirmed 1, 3

Common Pitfalls to Avoid

• Do not diagnose diabetes based on a single borderline value without confirmation testing 1, 3
• Do not confuse prediabetes ranges with diagnostic thresholds—HbA1c 5.7–6.4% and 2-hour glucose 140–199 mg/dL indicate prediabetes, not diabetes 1, 2
• Point-of-care glucose meters and HbA1c devices are not acceptable for diagnostic purposes; only certified laboratory measurements should be used 2, 4
• Ketosis alone does not establish a diabetes diagnosis; it is a complication or metabolic state that may occur in various conditions 1