The Hydration Balance

Most of us have been trained to be terrified of dehydration – in fact, beverage companies would have us believe that any time spent in a state of thirst is a near-death experience. Now the hysteria has flipped us too far in the opposite direction and dangerous overhydration – or hyponatremia – is a real problem for many athletes.


I never even knew overhydration could be a problem. After all, you hear so many new age health nuts talking about drinking three litres, four litres, seven litres of water a day and all they do is power yoga. Then I spoke to Dr Shane Brun, former President of Sports Doctors Australia and Associate Professor of Sports Medicine at James Cook University.

Over-hydration is just as dangerous as under-hydration,” he told me. “We see it a lot in fun runs, where athletes collapse because of overhydration – in fact, nowadays we’re probably seeing more people who are overhydrating than under hydrating.”

Drinking too much – even water – can be deadly, leading to a drop in sodium concentration in your body fluids that has the potential to be fatal. Kelly Barrett at the Chicago marathon in 1998, Cynthia Lucero at the 2002 Boston marathon, Hilary Bellamy at the 2002 Marine Corps marathon in Washington, DC, David Rogers at the 2007 London marathon – all died from hyponatremia. At the 1999 Houston Marathon, four runners were hospitalized with comas due to hyponatremia and at the 2002 Boston Marathon, 13% of 488 runners tested were hyponatremic. Yep, it’s that problematic.

Now in some ultra-endurance events, runners are weighed at the start then again at checkpoints, and they are held for observation or treatment if they have gained weight (believed to be due to water retention). Even at a moderate level, overhydration leads to reduced performance because your blood has to soak up some of the excess water in an attempt to equalize your body’s salinity. Cells begin to swell, causing all sorts of drama, from gastro to dizziness (yes, just like dehydration!), soreness and several of other symptoms that do nothing to make you faster.


Dr Brun explained that you need know what your baseline body weight is – that is, you jump on the scales in your undies before you go out and train – then weigh yourself the same way when you finish.

“Whatever you’ve lost in that hour or so is going to be fluid – not fat or anything else,” Dr. Brun said. “Every gram difference is one millilitre of fluid. So ideally, we keep people within 1-2% of their pre-activity weight. Up to 2% more or less, people can still function fine, but once you go over 2% in either direction, people’s performance is adversely affected.”

Slower people in longer events seem to be most at risk, because they might be sweating less and they have more time to over-drink without taking in enough sodium. Sodium (salt and chloride) is an essential electrolyte because it enables water to permeate cell walls so that water can be redistributed through the body, allowing muscles to work and organs to function.


Some groups of athletes are more prone to overhydration and/or dehydration. For example, masters and veteran athletes can have decreased thirst sensitivity once they’re dehydrated, which can make them less likely to rehydrate voluntarily. With age, the kidneys also tend to have a slower response to water and sodium loads, which can also put older athletes at greater risk of overhydration.

Women in general tend to have lower sweat rates than men, which can make female athletes more prone to overhydration. However, the group most at risk are those athletes with paranoia about dehydration – the real danger comes when they’re overhydrated and think they’re dehydrated because they haven’t urinated during training/competition (another symptom common to both dehydration and water toxicity) and so they drink even more. 

There have been 14 confirmed deaths from dehydration in athletes. Performing physical activity is the most common reason you might feel like your body needs more water than it actually does as you endure physical fatigue and rapid fluid loss. 

But don’t fall into the overhydration trap; drink enough to satisfy your thirst, and then continue on with your workout. If you feel like you are succumbing to the hydration temptation too often, try setting timers for yourself to space out your fluid consumption. This can include only allowing yourself a certain number of seconds of drinking each time you pause to hydrate. 

Some long-distance running advice suggests that you hydrate only every 20 minutes or so. Sticking to a solid routine such as this will ensure your body doesn’t become dehydrated but will also prevent you from drinking too much and falling into the hydration trap. 


Indications of water intoxication might include bloating, a feeling of fullness or a ‘sloshing’ of excess fluid in your stomach, nausea, poor absorption of food (from low sodium levels) and vomiting.

Neurological signs are bad news when it comes to the symptoms of overhydration. They indicate it’s time to see a medic for more severe cases if water poisoning. These signs include dizziness, drowsiness, incoherence, disorientation, irritability and possibly headache.

There are visible physical warnings, too – hands and wrists get tight and puffy (skin usually looks dry and loose with dehydration), urination may eventually come in high volume and crystal clear, and you might shiver when it’s not that cold.

Overhydration can escalate into a serious medical condition if your brain cells swell enough to interfere with the normal functioning of your central nervous system. This can lead to seizures, coma inductions, and even death if not properly treated.

If you believe you are experiencing any moderate to medium-level neurological symptoms, which can be precursors to the life-threatening side effects listed above, seek professional help immediately. 

What Happens Internally When You Overhydrate? 

When you experience hyponatremia, the sodium in your body will become less concentrated than it should be. This electrolyte imbalance can cause your water levels to rise, and your cells can swell abnormally in response. 

These electrolyte levels can lead to the symptoms listed above, ranging from mildly uncomfortable to serious life-threatening conditions. Depending on how severe your case is, you may be able to simply decrease your drinking and recover at home. If you are at the more serious end of hyponatremia, you may need medical help that can include electrolyteIVs or other medications. 


Taking salt tabs during a race as a preventative measure to offset sodium depletion or overdrinking is not recommended, because if you have adequate levels of sodium but you’re carrying too much water, adding a lot more sodium is not good. A deficiency of water or sodium can be corrected within minutes, but correcting excesses of either can take hours (and an IV drip!). Better to be conservative with the sodium so that if you have too much water on board then a one-time dose of electrolytes, along with sitting or walking, may prompt urination that will dump excess water. If you are craving salt, eat a salty snack. Your body will often tell you what it needs – you don’t always need to anticipate it!

So if you do long events, try to work out your ‘sweat rate’:

Litres per hour

( kg bodyweight pre-training – kg bodyweight post-training ­

+ litres drunk during training )

hours of training

Be aware that extreme conditions can throw off your usual sweat rate. For example, very dry or windy conditions can fool you into dehydration because the sweat evaporates too fast to be seen.


While everyone’s exact needs will vary based on physical characteristics such as gender, weight, and body type, there are a few baseline suggestions to help you get started when planning how much water to drink per day. 

General Water Consumption Suggestions

For adult men, the US National Academies of Sciences, Engineering, and Medicine recommend you drink around 3.7 liters (1 gallon) of fluids per day. For adult women, they recommend you drink around 2.7 liters (0.7 gallons). These numbers refer to overall fluid intake, which includes the water you get from foods. 

Water consumption through food usually accounts for around 20% of your daily fluid intake. This would mean that in terms of drinking straight water or other fluids, men should drink around 2.96 liters (0.8 gallons), and women should drink around 2.16 liters (0.56 gallons) each day. 

These recommendations refer to an average day for an average person, so adjust based on how you feel and if your urine is consistently light yellow or colorless, which indicates you’re getting enough water. 

You can also contribute to your daily water intake by consuming foods that have high water content. These will usually be vegetables and fruits like spinach or watermelon, and can minimize the amount of water bottles you have to go through per day.

The amount of water within your body at a given time is not only determined by how much you drink but also by how much your kidneys retain/eliminate. You want to be sure not to exceed your kidneys’ limit and consume more than they can eliminate in a timely manner.

In general, healthy adult kidneys can get rid of around 0.2 gallons of fluid every hour. Again, everyone’s individual limitations will be different, and no set amount of fluid intake will set you over the edge. Still, it is a good idea not to exceed this hourly limit if possible. Children and seniors may be unable to eliminate fluid as quickly, so be mindful of that when planning water consumption. 

Water Consumption for Exercise

If you exercise, you must consume additional water to replace the fluids you lose through sweat. There is no set recommendation for this because everyone’s body is different, and people exercise at different intensities. A general suggestion is to drink between 14-22 oz of water or sports drinks around two to three hours before your workout.

 If you consistently hit your recommended daily dosage of water, you can rest assured that you are properly hydrated and only need to drink a bit more to get through your workout. This peace of mind will hopefully alleviate any concerns or paranoia about not being hydrated enough and prevent you from accidentally overhydrating. 

Hydrating in the Heat vs. the Cold

It’s no secret that running or training in the hot summer sun causes your body to sweat more, increasing your fluid loss and encouraging you to drink large amounts of water. While summer weather technically is more conducive to dehydration, you will probably be craving water and more likely to pack enough fluids since you will be conscious of the heat and come better prepared. 

So yes, drink a lot of water to replace the fluids you lose from sweat, but again, drink intermittently throughout your workout and in moderation to prevent excessive water intake and overhydration.

In colder weather, your body will most likely not sweat as much or crave water to the extent that you do in the summer. This does not mean you don’t need water, so pack a bottle or two and drink occasionally before and throughout your workout to prevent dehydration. But as always, don’t let the paranoia of dehydration push you over into the dangerous realm of overhydration. 

Check out our selection of warm and water-resistant men’s running jackets and vests for support and protection in cold and rainy weather. Options for women can be found here


Remember that mild dehydration – around 2% of your normal weight (i.e. [0.02 x kg bodyweight] x litre) is not dangerous or even detrimental to performance – and it’s easy to quickly correct. There is no need to panic and try to drink an excessive amount of water to compensate. Allow your body to recover, and if needed, drink water in moderation to help the process. You will be just fine!


Water: How much should you drink every day? - Mayo Clinic

Are you over-hydrated? - Gundersen Health System.

Overhydration: Types, Symptoms, and Treatments