How come i get so sleepy when i am hungry?

Cerebral Metab Dys: The only source of energy your brain has available to it is glucose. When not present there is decreased cerebral metabolism and that can result in intellectual, motor and emotional dysfunction. One of those manifestations is sleepiness and lethargy. It is worth investigating as the treatment is different depending upon the cause. A 2 hour glucose tolerance test can be useful. Good luck.