The American Diabetes Association suggests that a person having a hypoglycemic episode be given 15 g of glucose PO, if (s)he can still protect his/her own airway.  Administering a measured amount is essential to preventing rebound hypoglycemia.  Having glucose in gel form also allows the rescuer to place small amounts in the buccal mucosa for absorption when the patient is not conscious enough to swallow, buying a small amount of time while you are waiting for paramedics to arrive.