In an elderly patient presenting with syncope, which laboratory test is important to perform initially?

• A. Electrolyte panel
• B. Blood glucose
• C. Complete blood count
• D. Lipid panel

Answer: (B)

Testing blood glucose early in syncope is crucial because hypoglycemia is a common, immediately reversible cause of fainting, and elderly patients are especially at risk due to diabetes medications, irregular meals, and impaired counterregulation. A quick bedside glucose check can quickly identify or exclude hypoglycemia as the culprit, allowing prompt treatment with fast-acting carbohydrates if needed and preventing further decline in mental status or consciousness.

While electrolyte disturbances, anemia, or lipid abnormalities can contribute to fainting or indicate broader issues, they do not require the same immediate action and are less likely to change the initial management in the acute setting. An electrolyte panel and CBC are useful as part of a broader workup, but the glucose result directly informs urgent treatment decisions and safety.