In the case of a 29-year-old diabetic man who becomes unconscious, what is the most appropriate initial investigation?

In this scenario, where a 29-year-old diabetic man becomes unconscious, the most appropriate initial investigation is random blood sugar. This is crucial because unconsciousness in a diabetic patient can often be attributed to either hypoglycemia (low blood sugar) or hyperglycemia (high blood sugar).

Measuring the random blood sugar is a rapid and effective way to assess the immediate cause of the patient's altered state of consciousness. If the blood sugar is low, it could indicate hypoglycemia, which requires prompt treatment with glucose. Conversely, if the blood sugar is high, appropriate management for hyperglycemia should be initiated. Thus, determining the blood sugar level is vital for guiding immediate treatment to stabilize the patient.

Other investigations, such as a CT scan, MRI, or ECG, while potentially important later in the clinical assessment, do not provide immediate information regarding the most critical and reversible causes of unconsciousness in a diabetic patient, which are primarily related to blood glucose levels.