I could write pages on this subject, but here goes for now. Blood sugar levels are critical for everyone, but especially for people with metabolic disorders (diabetics & adrenal insufficiency), being prone to hypoglycemia (too low of blood sugar, like below 60 for a child). A blood sugar level of 30 or below can cause brain damage, unconsciousness, seizures, and lead to death from all of this. Blood glucose provides energy for the body AND is the "brain's main food" (glucose is what carries oxygen to the brain). I am positive ANY dehydration will cause their glucose metabolism systems to not function correctly, and that they are at risk of hypoglycemia. Cortisol is responsible for maintaining blood glucose production AND glycogen storage AND glucose transport to brain & cells. If you get into a low blood glucose situation (which the body dealing with a low blood glucose situation provokes stress thus requiring even more glucose to deal with that "low glucose stress"): the body will use up all 'already made blood glucose', then will go to the stored glucose (called glycogen - incidently without sufficient cortisone, the glycogen may "pour" out the urine & none is going into storage at a point, also cortisone is needed to convert that stored glycogen into usable blood glucose AND transport it to the blood). If there is no glycogen in storage, then the body begins using up all available protein from cells, muscles(?), etc. to make glucose (which in doing this glucose is used up at a faster rate than can be made). I've got notes on all this regarding what organs do what, very detailed. Hence, lethargic & tired child, no energy because glucose is what provides energy. Muscle tiredness, unclear thinking, etc. HOWEVER, THERE IS SOMETHING CALLED HYPOGLYCEMIC UNAWARENESS THAT ADRENAL INSUFFICIENT PEOPLE CAN HAVE .. which means their bodies are SHOWING NO SIGNS OF LOW BLOOD GLUCOSE (dizziness, lethargy, headache, etc.) ... until they literally pass out or worse. I keep blood glucose tablets on hand (so cheap, like $1.50 for a 10-pack).