Can I actually drink too much water?

It is possible to drink too much water. Doctors call this water intoxication. Water intoxication may cause electrolytes, such as sodium and potassium, in your bloodstream to get low. Low electrolytes can cause symptoms such as confusion or weakness. Water intoxication is rare. It is much more common for someone to be dehydrated from not drinking enough water than for someone to have water intoxication. When water intoxication occurs, it is usually in a patient who suffers from a psychiatric problem. In some of these cases, patients are drinking several gallons of water every day. It is hard to say how much water is too much, as we are all different, but generally, a healthy person would have to drink very large amounts of water to experience water intoxication.
A rare condition called hyponatremia (also known as water intoxication) can occur when extreme amounts of water are consumed during strenuous activity (more than 4 hours). In this condition, water intake is well beyond the amount of sweat loss, and there is not enough sodium (salt) in the body. Generally, the body cannot remove the excess water quickly enough.

Acute hyponatremia (occurring in less than 48 hours) can be a serious, life-threatening condition. Common symptoms include confusion, decreased consciousness, hallucinations, irritability, convulsions, fatigue, nausea, vomiting, headache, and muscle cramping. This rare condition can be prevented if sodium or a sports drink containing sodium is consumed during and after strenuous activity.

(This answer provided for NATA by the Appalachian State University Athletic Training Education Program.)
Dr. Michael Roizen, MD
Internal Medicine
Water intoxication or sickness from drinking too much water occurs where you exceed your capacity to get rid of water. Your capacity to excrete water is normally about 1000 milliliters per hour (which is about 4 glasses), so if you drink more than this, you will dilute your body salts.

If the capacity to excrete water is impaired, then even lesser rates of consumption will result in low sodium concentration in your blood. Kidney failure is one reason for such an impaired capacity. The other, major reason for a failure to excrete a water load is the presence of a hormone vasopressin--the antidiuretic hormone. This last explains the frequency of low sodium concentration in the blood in marathon runners: marathon runners sweat and become volume depleted, vasopressin rises, thirst increases and due to the vasopressin, the water load cannot be adequately excreted and salt concentration falls.
YOU: The Owner's Manual, Updated and Expanded Edition: An Insider's Guide to the Body that Will Make You Healthier and Younger

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YOU: The Owner's Manual, Updated and Expanded Edition: An Insider's Guide to the Body that Will Make You Healthier and Younger

Between your full-length mirror and high-school biology class, you probably think you know a lot about the human body. While it's true that we live in an age when we're as obsessed with our bodies as...

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Plenty of water in your diet helps digestion, skin, and muscle tone. It can help prevent cramping during exercise and even relive stress. Many times we are low on water - dehydrated, and don't realize it. Being dehydrated can mani...

fest with symptoms like fatigue and depression. In fact, by the time we are feeling thirsty, we're already slightly dehydrated. That's one reason that we hear the recommendation to drink eight standard glasses of water daily. Adequate water helps you digest food an helps your body get rid of wastes. Your kidneys need to process water for you to eliminate waste by urination, and getting enough water ensures that these wastes are diluted. Not getting enough water can encourage the formation of painful kidney stones.

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.