Dehydration

Having enough water is essential to your body's proper functioning. When you are well-hydrated, your body can process and eliminate wastes and carry nutrients to the cells that need it. Dehydration leads to a whole array of problems related to these functions.
Often, we are dehydrated and don't even realize it. It is very easy to mistake the symptoms of dehydration for other problems. Your first response to any symptom should be to drink plenty of water. Even if your ailment isn't directly caused by dehydration, being properly hydrated will help your body to effectively combat any issues.
These are direct signs that you are dehydrated, sometimes severely so:
-Dark urine
-Dizziness
-Inability to urinate
-Weakness and fatigue
-Dry mouth and tongue
Your first reaction should be to drink water - not coffee, not soda, but water.
Many of symptoms of dehydration are mistaken as other issues, often easily resolvable. Of course, if your problem is not solved by this measure, be sure to seek additional means of treatment.
-Often, we mistake thirst for hunger. When you feel hungry, have a glass of water first, then see if you are still as hungry.
-Exhaustion. Many times we feel terribly in need of some coffee, or a nap, when we really just need a drink of water. If you still feel exhausted after a glass or two, you may have low blood sugar, or truly be in need of a nap....or caffeine, if you really must.
-Acne, to some extent, can be caused by dehydration. Dehydration stresses the body, which leads to breakouts. The inability to process and expel of wastes leads your body to desperate measures - expelling waste through the skin. Also, when you are dehydrated, your skin can get too dry. The body will feel the need to respond by excreting oils, which can build up and contribute to skin problems.
-Headaches often stem from dehydration as well, as well as many other muscle aches.
Watch out for causes of dehydration. It is easy to become dehydrated due to the following:
-Heat exhaustion
-Diarrhea
-Exercise
-Swimming (a bit unexpected, perhaps)
-High blood sugar
-Consumption of alchoholic beverages
When you are ill and go to the doctor's office, there is a reason you are told to "rest and get plenty of fluids". Your body is greatly in need of these fluids in order to function optimally.