High: Makes you pee more
Your kidneys have to work hard to process all that extra sugar in your blood. When they cannot keep up, your body gets rid of it, along with water that your body needs.
High: 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 are thirsty so you will drink more.
High: Dry mouth
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.
High: Skin problems
Your body takes water from all over to get rid of extra blood sugar. That may cause dry, itchy, cracked, skin, especially on your legs, elbows, feet and hands. In time, high glucose levels also can damage nerves. This is called diabetic neuropathy. It can make it harder for you to feel cuts, wounds or infections.
High: Vision problems
Your body may pull fluid from the lenses in your eyes, which makes it harder to focus. And high blood sugar can damage blood vessels on the back part of your eye. That can cause long-term vision loss and even blindness.
If you have diabetes, insulin is one way to lower your blood sugar when it gets high. But if you take too much, it might remove so much glucose so quickly that your body cannot replace it fast enough. That leaves you tired.
Low: Weird heartbeat
The hormones that help raise your blood sugar when it is too low can also spike your heart rate and make it feel like it skips a beat. The drop in glucose most often happens as a side effect of drugs used to treat diabetes.
Low glucose can unsettle your central nervous system which controls how you move. When that happens your body releases hormones like adrenaline, to help bring your levels back up. But those same substances also may make your hands and other parts shake or tremble.
The hormones your body releases to raise your blood sugar when it gets too low also make you sweat a lot. It is often one of the first things you notice when your glucose levels fall too far. Your doctor can help you track your levels and try to keep them in a healthy range with medication, exercise and eating habits.
Actually, it is not low blood sugar by itself. When your levels get either very high or very low it can cause a rebound effect. Your blood sugar bounces from one extreme to the other, confuses your body's digestive system and makes you feel sick to your stomach.
When your blood sugar gets really low, you start to lose your bearings. You may slur your speech or forget where you are. Sometimes it happens so suddenly that you might not even realise you are acting strangely. In serious cases, you could have a seizure or fall into a coma.