What should be done if a passenger is unconscious from low blood sugar?

When a passenger is unconscious due to low blood sugar, the appropriate action is to use a gloved finger to place sugar between their cheek and gums. This method allows for rapid absorption of glucose directly into the bloodstream through the mucous membranes in the mouth. Since the individual is unconscious, they are unable to swallow safely, making it crucial to avoid giving them solid food or drinks that could lead to choking.

Administering insulin is not appropriate in this situation, as insulin is used to lower blood sugar levels, and the passenger's issue is low blood sugar. Placing them upright in their seat may also not be safe or effective, especially if they are unconscious, as it can lead to airway obstruction. Offering solid food is also risky, as the passenger may not be able to swallow properly, which could lead to choking hazards.

Using sugar in the manner described in the correct answer provides a safe and effective way to help manage the symptoms of low blood sugar while minimizing risks associated with unconsciousness.