Hydration is defined in the American Heritage Medical Dictionary as “the process of providing an adequate amount of liquid to bodily tissues.” The word I'd like to emphasize here is adequate. I'm placing emphasis here because I mean to stress the important fact that you need just the right amount of hydration. No more, no less. You want to drink enough fluids to get and keep your body hydrated while still being mindful not to over-drink and cause damage.
Dehydration is, “excessive loss of water from body tissues. Dehydration is accompanied by a disturbance in the balance of essential electrolytes, particularly sodium, potassium, and chloride. It may follow prolonged fever, diarrhea, vomiting, acidosis, and any condition in which there is rapid depletion of body fluids. It is of particular concern among infants and young children that their electrolyte balance is normally precarious. Signs of dehydration include poor skin turgor (not a reliable sign in the elderly), flushed dry skin, coated tongue, dry mucous membranes, oliguria, irritability, and confusion. Normal fluid volume and balanced electrolyte values are the primary goals of therapy.” as defined by Mosby's Medical Dictionary, 8th edition. © 2009, Elsevier. Some of the first signs of dehydration include dry mouth, fatigue, headaches, and difficulty concentrating. If you begin to experience these symptoms, simply drink a glass of water and continue to do so until your thirst is quenched.
Now I'll talk about something you may not have even heard of, let alone know a lot about. Overhydration. Also referred to as hyperhydration, Mosby's Medical Dictionary, 8th Edition © 2009, Elsevier defines overhydration as “excess of water in the body.” This condition is the polar opposite of dehydration. It is most common among those who have difficulty with kidney function as they have trouble regulating the water content and/or water retention of their body. This would tend to cause the sodium level of the blood to be lower than it should be. An article that is very informative on this topic is “Over-drinking can be deadlier that dehydration” written by George Winter. It brings to light a very often looked-over yet serious condition that everyone should be aware of.
At this moment you may be thoroughly confused and most likely frustrated, here's a helpful hint. Stick to the staple 64 ounces (2 liters) of water daily. That is equivalent to 6-8 glasses of water per day. If you have any sort of kidney conditions however, I recommend talking to your doctor about how much water you are supposed to be taking in per day. The numbers may be different for you.