5. You Have Become Fatigued and Lethargic
Blood contains water, and if your body lacks water, it starts borrowing it from the blood. The problem is that sooner or later the blood gets dehydrated as well and then cannot deliver oxygen to your brains cells and other organs. What makes you feel lethargic and fatigued is a lack of oxygen. Do not try to replace water with coffee. The only thing that can help you is water.