Hyponatremia: Drinking too much Water?

Florence Barrett-Hill

Can one drink too much water? How much is too much?

These questions are often asked by therapists when addressing conditions of the skin that are affected by low water content of the body or an impaired lymphatic system. So with a little research into the world of sport, I came up with an answer.


Within the last few years the condition known as hyponatremia has begun to attract the attention of sports medicine physicians, exercise physiologists, and the medical directors at some of the larger marathons around the country. Hyponatremia has been called water intoxication because of the symptoms it produces. According to Dr. Tim Noakes, Professor of Exercise & Sports Science Director at the University of Cape Town, “a person with hyponatremia looks like he or she is mildly drunk. They can’t concentrate normally, they forget what you were talking about and start to concentrate elsewhere.”

People with Hyponatremia have an imbalance of water and sodium

Hyponatremia occurs when the body becomes dangerously low in sodium. It’s caused when you literally take in too much water. Although scientists have known about it for a long time, it has only become a concern in the last few years, as more runners have been competing in marathons.

According to Dr. Noakes, fluid has to be ingested at high levels for several hours for hyponatremia to occur. He suggests that a runner would have to be drinking water regularly for at least four to six hours to develop the condition.

So runners taking four to six hours or more to run a marathon are at particular risk.

Unfortunately, symptoms of hyponatremia tend to mimic those of severe dehydration and/or heat exhaustion.
By giving the athlete more water to drink the hyponatremia becomes worse, as more and more sodium is flushed out of the system. If a runner with hyponatremia is given fluids intravenously, they can suffer a fatal reaction.
Dr. Noakes and other sports medicine professionals recommend that physicians and other medical personnel at road races be alert for the signs of hyponatremia. One of the earliest symptoms is a craving for salty food.

Normal balance

Although hyponatremia is rare, it is wise to be aware that it can occur, particularly if you’re running a marathon in unusually hot weather. Hyponatremia serves as a reminder that water is good, but don’t forget sports drinks, which replenish your body with the sodium, potassium and other trace minerals you lose through sweat. It is worth repeating: if you’re going to be running (or racing) for longer than an hour, you should be drinking a sports drink as well as water.

Heat Cramps

Have you ever seen a runner bent over at the side of the road massaging their calves during a race? Chances are that he or she had heat cramps. Heat cramps are very painful and rarely “work themselves out”.

The cramps occur because you’ve lost minerals through sweating and dehydration.
Once you’ve reached the point of heat cramps, it is too late to try to replace fluids on the run.
To make the cramps go away you should:

  • Stop running
  • Drink fluids immediately.
  • The fluids should include sports drinks as well as water
  • Massage the muscles once the pain begins to subside
  • Cool your body with wet towels
  • Get out of the sun

Heat Exhaustion

Heat exhaustion is a very serious condition that can lead to heatstroke. The symptoms of heat exhaustion are:

  • Dizziness
  • “Goosebumps” (particularly on the torso and arms)
  • Nausea (sometimes accompanied by vomiting)
  • Moderate to severe headache
  • Weak legs
  • Lack of coordination
  • Rapid pulse
  • Heavy sweating often accompanied by moist and cold skin

Muscle cramping

If you experience any of these symptoms you must:

  • Stop exercising or running immediately
  • Get medical attention
  • Drink large amounts of fluids, including sports drinks
  • Get out of the sun
  • Lie down and elevate your feet above your heart
  • Loosen your clothing


Heatstroke can be fatal. Unfortunately, runners will sometimes ignore the symptoms of heat exhaustion (particularly in races longer than 10K) and will continue to push themselves until they’re nearing a total thermoregulatory breakdown. The symptoms of heatstroke are very similar to those of heat exhaustion, but rapidly progress to:

  • Disorientation
  • Weakness in the legs to the point that the runner may fall
  • Strange behaviour (including flailing with the arms and shoving)
  • “Fuzzy” thinking
  • Rapid pulse
  • Cessation of sweating and hot/dry skin
  • Body temperature that may reach 104 degrees or higher
  • Lack of consciousness
  • Convulsions or seizures
  • Coma

Someone suffering from heat stroke needs immediate medical attention. They should be moved out of the sun, cooled by either rubbing their body with ice or immersing them in cold water and given fluids intravenously.

Internal Dehydration

Internal Dehydration is not limited only to the summer months, although it is probably more likely to occur during that time. Many physicians believe that most people are in a constant state of dehydration. Since coffee, tea, soda and alcohol act as a diuretic, anyone who drinks these fluids on a daily basis, and doesn’t drink at least an equal amount of water, will probably be dehydrated. If the person is physically active, the potential for dehydration is even greater.

Working out in hot, humid conditions promotes sweating, which in turn can cause dehydration. Sweating is good for you because it cools your body, but when you lose too much water you become dehydrated. If you’re already slightly dehydrated, sweating will only make it worse. It’s important to maintain an adequate fluid intake all the time. Don’t expect that you can make up for several days of not drinking enough by downing an electrolyte drink. It’s important to keep hydrated all the time. Once you start to feel thirsty, it is too late.

The average (sedentary) person needs a minimum of eight 8-ounce glasses of fluid a day. Highly active sports people need more: at least sixteen 8-ounce glasses daily. Drink water and sports/electrolyte drinks, and if you don’t have to worry about calories, fruit drinks or juice.

Two hours before your daily summer workout or a run, you should drink 16 ounces of fluid. Then ten minutes or so before you start to run, drink another one or two cups of water or a sports drink. Drinking early and drinking often is the key. During a race, you should drink six to twelve ounces of fluid every 15-20 minutes.
If the weather is very hot, you may need to drink even more. Training in warm weather, you should drink at least every 35 to 40 minutes. (Remember you will have already had two 8-ounce glasses before you started.) If you’re running a race shorter than 30 minutes, you probably won’t need any water other than what you drank before the start. The same goes for the last few miles of a longer race. If you’re racing or training for longer than an hour, drink sports drinks as opposed to strictly water.

Start drinking immediately after finishing a run, no matter if it was a race or a workout. Minimum is 16 ounces for every 30 minutes you ran. If you tend to sweat a lot, you’ll need more. Weigh yourself after you’ve run. Drink at least 16 ounces of fluid for every pound you lose through sweating.

By monitoring the colour of your urine you can tell if you’re hydrated. It should be pale yellow or even clear. If it isn’t, you need to drink more fluids. It’s important that you retain the fluid, so be careful if you’re urinating every fifteen or twenty minutes.
To restore your fluid balance, eat something salty (a bag of pretzels, salted nuts, crackers or potato chips), then drink a sports drink. The salt will make you thirstier, so you’ll take in even more fluid and urine production will decrease.

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