Your kidneys have to work hard to process all that extra sugar in your blood. When they can't keep up, your body gets rid of it, along with water that your body needs
Makes you Thirsty
To get rid of that extra sugar, your body draws water from its own tissues. Because you need that fluid to make energy, transfer nutrients, and get rid of waste, a switch flips in your brain to tell you that you're thirsty so you'll drink more.
Your mouth could get dry and cracked at the corners as your body draws fluid from it. Less saliva and more sugar in your blood make infection more likely. Your gums might swell, and white patches can grow on your tongue and inside your cheeks.
Your body takes water from all over to get rid of extra blood sugar. That may cause dry, itchy and cracked skin, especially on your legs, elbows, feet and hands.
Your body may pull fluid from your lenses in your eyes, which makes it harder to focus. High blood sugar can damage blood vessels in your retina causing long-term vision loss and even blindness.
When your blood sugar is high too often, you become less sensitive to insulin, which helps move energy to your cells. A lack of fuel can make you tired.