What is the A1c threshold for diagnosing diabetes?

• A. 5.7% or higher
• B. 6.5% or higher on two separate tests
• C. 6.0% or higher
• D. 7.0% or higher

Answer: (B)

A1c is used to diagnose diabetes when the result is 6.5% or higher, and it must be confirmed on a second test performed on a different day. This threshold reflects a level of average glucose over the previous two to three months that is clearly associated with increased risk of diabetic complications, especially those affecting small vessels like the retina and kidneys. Requiring two separate elevated results helps ensure the finding is persistent and not due to a temporary factor, lab variability, or an acute illness.

Understanding the other numbers helps clarify why they aren’t diagnostic thresholds: 5.7% falls in the range labeled prediabetes, indicating higher risk but not diabetes. A reading around 6.0% is still considered prediabetic. A value of 7.0% is above the diagnostic threshold and is commonly used as a treatment target for many patients with established diabetes, rather than as the criterion to diagnose the disease.