How is a diagnosis of diabetes mellitus confirmed?

For the diagnosis of diabetes mellitus, the following criteria are used:

- Fasting plasma glucose (FPG) level: This is the glucose level measured in blood plasma after an 8-hour overnight fast. A fasting plasma glucose level of 126 mg/dL (7.0 mmol/L) or higher on two separate occasions indicates diabetes.

- Oral glucose tolerance test (OGTT): This test measures the body's ability to process glucose. After an overnight fast, a person drinks a standardized glucose solution, and their blood glucose levels are measured at specific intervals over the next 2-3 hours. Diabetes is diagnosed if the 2-hour plasma glucose level is 200 mg/dL (11.1 mmol/L) or higher.

- Random plasma glucose level: A random plasma glucose level of 200 mg/dL (11.1 mmol/L) or higher is also used to diagnose diabetes. This test does not require fasting and can be done at any time of the day.

- Symptoms and signs of diabetes in conjunction with random, fasting, or 2-hour post-load plasma glucose levels greater than or equal to the values suggested above: The symptoms of diabetes, such as increased thirst, frequent urination, and weight loss, may also be present.

It's important to note that diabetes is diagnosed when any of these criteria are met on two separate occasions.