Which of the following is a diagnostic threshold for diabetes?

• A. Fasting plasma glucose ≥126 mg/dL on two occasions.
• B. HbA1c ≥6.0%.
• C. Random plasma glucose ≥180 mg/dL with classic symptoms.
• D. 2-hour OGTT ≥250 mg/dL.

Answer: (A)

A diagnostic threshold for diabetes relies on clear, repeatable evidence of chronic hyperglycemia. The most established criterion is a fasting plasma glucose of 126 mg/dL or higher, confirmed on two separate occasions. Requiring two separate tests helps avoid misclassifying someone due to a one-time fluctuation or temporary illness, ensuring that the elevated level reflects persistent hyperglycemia.

Other ways diabetes can be diagnosed include an HbA1c of 6.5% or higher, a random plasma glucose of 200 mg/dL or higher when classic symptoms of hyperglycemia are present, or a 2-hour plasma glucose after an oral glucose tolerance test of 200 mg/dL or higher. The values given in the other options do not meet these standard diagnostic thresholds—180 mg/dL with symptoms is not a diagnostic cut-off, and 250 mg/dL at 2 hours is higher than the official threshold of 200 mg/dL for the oral glucose tolerance test.

So the strong, repeatable fasting glucose criterion best fits the official diagnostic standard for diabetes.