What is one criterion for diagnosing diabetes?

One criterion for diagnosing diabetes is a fasting plasma glucose level greater than 126 mg/dL after an overnight fast (at least 8 hours). This measurement is significant because it reflects how the body regulates blood sugar levels when no food has been consumed for a period, thus providing a reliable indicator of insulin function and glucose metabolism.

A level above this threshold suggests that the body is unable to maintain normal glucose levels, which is a hallmark of diabetes. This test is widely accepted and used in clinical practice due to its straightforward preparation and the clarity of results, making it an essential method for early diagnosis and management of diabetes.

In contrast, while the other options may indicate issues related to glucose regulation, they do not meet the established criteria for diagnosing diabetes according to medical standards. For instance, an A1C level above 5.5% may suggest a risk of diabetes or impaired glucose tolerance, but it does not reach the diagnostic thresholds required for diabetes. Similarly, random blood sugar above 180 or 2-hour plasma glucose over 150 during an oral glucose tolerance test are valuable in specific contexts but are not definitive on their own without other confirmatory tests.