How is the diagnostic evaluation of hypoglycemia?

Whenever we have a pt with syncope/ pre-syncope, first thing to do is obtain blood glucose concentration, if it is low (<55) draw blood for glucose, insulin, C-peptide, and oral hypoglycemic agent. If it is symptomatic, we shouldn't delay the treatment of the etiology. If we can't undergo these, go for 72-hour fasting test.