How is diabetes mellitus diagnosed?

Diabetes mellitus is primarily diagnosed by measuring fasting glucose levels because this method reflects the body's ability to regulate blood sugar in the absence of recent food intake. Fasting glucose tests typically require the patient to fast for at least eight hours before the test, ensuring that the measurement reflects baseline blood sugar levels without the influence of recent meals. A fasting glucose level of 126 mg/dL (7.0 mmol/L) or higher on two separate tests is indicative of diabetes.

While other methods, such as urine tests for ketones or a complete metabolic panel, provide valuable information, they do not specifically diagnose diabetes. Urine tests primarily help assess the presence of ketones, which can occur in people with diabetes but are not used for initial diagnosis. A complete metabolic panel analyzes various electrolyte and enzyme levels, which may suggest metabolic imbalances, but it is not specific for diagnosing diabetes. Imaging techniques like X-rays of the pancreas are not relevant for diagnosing diabetes mellitus, as they do not provide information about blood glucose levels. Therefore, measuring fasting glucose levels remains the gold standard for diabetes diagnosis.