Why Increase fluid intake for fever?

One reason might be that your blood volume is too low causing low blood pressure.Low blood pressure can make you feel light-headed and is dangerous because you need your blood to be able to deliver oxygen to your brain and the rest of your body. You can increase your blood volume and hence your blood pressure by increasing your fluid intake.Also,when you are dehydrated your body can become deficient in certain things such as sodium,potassium,etc. Your body is like an engine in that it needs fluid to work properly.Drinking enough water is one of the best things you can do to keep yourself healthy.