u/CryingGalaxies

I am writing this almost 12 hours before my exam and I do not have the time to research this lol, so I was wondering if anyone here knows the answer to the title. I plan on having the normal breakfast that I usually have, but that would already by 3 hours before the exam starts. My question is, is my optimal brain performance influenced by my glucose levels? Should I have a sugary snack before entering or not?

For refrence, my exam will be 3 hours and 30 minutes long and nothing edible besides water is allowed (albeit for medical purposes).