What laboratory test is used to diagnose diabetes mellitus?

The appropriate laboratory test for diagnosing diabetes mellitus is the Hemoglobin A1c Test. This test measures the average blood glucose levels over the past two to three months by assessing the percentage of hemoglobin that is glycated (attached to glucose).

Using the A1c test is beneficial because it provides a broader perspective of glucose control compared to a single blood glucose measurement, thus allowing clinicians to diagnose diabetes and monitor long-term glucose control. An A1c level of 6.5% or higher is typically indicative of diabetes mellitus.

While the Oral Glucose Tolerance Test (OGTT) is indeed another method used to diagnose diabetes, it assesses how well the body processes glucose after fasting and ingesting a glucose solution, making it a valid option but not the most frequently used initial screening tool. The OGTT can be more cumbersome for patients and typically requires more time to complete compared to simply drawing blood for A1c levels.

The Complete Blood Count (CBC) and Liver Function Tests (LFTs) serve different purposes and are not suitable for diagnosing diabetes. A CBC is primarily used to assess overall health and detect a range of disorders, while LFTs evaluate the liver's health and functioning. Therefore, they do not provide information