What test should be performed for a patient presenting with polydipsia, polyuria, and polyphagia?

In evaluating a patient with symptoms such as polydipsia (excessive thirst), polyuria (frequent urination), and polyphagia (increased hunger), monitoring blood glucose levels is essential for diagnosing diabetes. The HbA1c test measures the average blood glucose levels over the past two to three months, providing a comprehensive view of a patient's long-term glucose control and aiding in the diagnosis of diabetes mellitus.

When a patient presents with these symptoms, the underlying concern often revolves around the possibility of diabetes, particularly Type 1 or Type 2 diabetes. The HbA1c test is a standard tool used in clinical practice to determine if a patient's glucose levels are consistently elevated, which aligns with the common presentation of diabetes. An HbA1c level of 6.5% or higher is indicative of diabetes.

Other tests mentioned, such as the blood urea nitrogen test, primarily assess kidney function and may not directly relate to symptoms indicative of diabetes. The thyroid function test evaluates thyroid hormone levels, which can influence metabolism but may not specifically address the symptoms described. The glucose tolerance test, while also relevant for diagnosing diabetes, is often considered in specific situations like gestational diabetes or when a confirmation of diabetes is needed after abnormal initial