You can't poop
Feeling backed up? Grab that water bottle, and hopefully you'll get back to feeling like Jamie Lee Curtis after some yogurt.
"Dehydration can also lead to constipation," Dr. Burchett confirms. "Our intestines need water to digest food and move waste through. I have seen tons of patients who are constipated largely from inadequate water intake. Often they don't need a laxative, they just need more water. I think of water as lubrication for the intestines."
You generally feel like trash
You know that feeling when you have some sort of indeterminate illness that knocks you out for a few days, and you just call it a cold or flu? Lack of water might just be a cause of some of those symptoms. Headaches and sleepiness. Achiness, lethargy, and general grossness. That's all because blood volume and blood pressure drop when you're dehydrated, then muscle and nerve functions slow, and thus, fatigue sets in.