A 23 year old male has a tonic clonic seizure whilst at college. His GCS is 12, BP 120/77mmHg, HR 99bpm. What is the most appropriate investigation for his condition?

The key is C. Serum blood glucose [it is also possible that he may have taken drug, even though first we have to do serum glucose as low blood glucose can be very easily managed and it needs urgent management to save life. If it is excluded then we can look for other causes which may be not fatal in short time as hypoglycaemia].