I just know from my daughter-- she doesn't want to move. When she is hydrated properly, and electrolytes balanced, she has plenty of energy. By the way, doctors will rarely diagnose this. Blood tests generally are all within normal ranges, unless the problem is really horrible. But there are clues from the blood tests--WHERE in the range is everything? In my daughter, her sodium tends to get on the low side, whereas the potassium is normal or a little high. The electrolyte mix needs to take into account the particular person, and not just assume potassium is low, like many do. They make matters worse for her.
Pedialyte is good because it is formulated for babies, and there is simply no margin of error there, and no assumptions made about the sodium/potassium ratio.
Two of my daughters have had problems with electrolyte balance. The other one gets swollen ankles.
Some things that can affect electrolyte balance--stomach upsets, drinking alcoholic beverages, sweating, as in being out in the sun, and sometimes drinking coffee or tea.
Pedialyte is our second choice for electrolytes, only because of the taste and the glucose in it. But it is readily available.
Generally we try to order the green label concentrated bottle of electrolytes found here--Most people need the green label electrolytes--just a few need the unbalanced ones.
http://www.lifebalancesprogram.com/products.html