Hydration and Salt Levels For Runners – Explained

Hydration for runners levels explained here!  Keeping yourself hydrated is important during long runs, but that doesn’t mean you should just drink as much water as you can.  There’s an appropriate amount to drink – not too little, not too much.   Salt balance is also important – as we sweat, our body loses salt which we should replace.   In this article, I look at how to manage hydration and salt levels on long runs.

Hydration and Salt Levels For Runners - Explained 1

Hydration for Runners

On shorter runs – say anything less than 10km – hydration shouldn’t be a huge issue.   If you’re out for 30-45 minutes, then unless you are in a high temperature environment then its fine to replenish your fluids after you finish your race.

Once you get into longer distances, you’ve got to be mindful of your hydration levels.   If I go out for anything over a 30 minute run, I’ll be drinking water while I’m running.  

There’s a balance in how much water to drink – and many runners wrongly think it is better to err on the safe side and drink too much water, as opposed to not enough.   Drinking too much can lead to stomach slosh, or – much worse – hyponatremia, if you completely mess up your salt balance.  Hyponatremia really only occurs in extreme circumstances – but I’ll cover it later so you’re aware of the risks.

Likewise, dehydration during a run can lead to a headache after running and medical issues, and certainly doesn’t do your kidneys any good.  

It’s been much quoted recently that many more people have died of over-hydration than dehydration during athletic events.  With this in mind, the current medical advice for performing activities where you sweat a lot is to just drink when you begin to feel thirsty.   This has also been described as ‘drinking a sufficient amount to prevent thirst’.

Regarding consumption rates, 500ml/hr is regarded as a minimum amount.   Typically in a distance running event, each aid station will offer 1.5l of water – I find this to be an adequate amount for the average runner to consume over 10km in hot conditions – many people find this to be excessive.

Personally, I find that using a bottle with a straw-like sipper makes staying hydrated very easy.   I take tiny sips of water all the time, and find this is an effective way of balancing my hydration.  

As with every aspect of distance running, the trick with keeping your hydration balanced is in the training – experiment with different quantities when you go for a run, and find out what suits you.
Water should be consumed gradually and continuously over a run, in small sips rather than large volumes.

Dehydration and distance running can lead to running with hemorrhoids.

salts and hydration


Humans are salty animals – our blood has the same salinity as seawater.  When we run long distances, we sweat – and replace the sweat with fresh, clean water.  The problem is, we lose a lot of salt through our sweat, so we’ve got to look at ways of replacing the salt too.


Ultra-runners have ended up in comas from drinking too much water and not replacing their salts – this condition is known as hyponatremia.  The sudden dilution of your system and lack of minerals throws your body into a tailspin, leading to disorientation – then it can escalate quickly from there. Don’t worry too much about hyponatremia – as long as you are conscious of your salt and hydration levels, it’s extremely unlikely you’ll have any issues.

How to take salts

The simplest way to replenish your body’s salt level is with salty snacks, or salt capsules – tiny dissolvable pills that are pure salt.  Easy to swallow, compact and handy.  I’ve always stuck to Saltstick capsules – simple and easy to use.
Hydration and Salt Levels For Runners - Explained 2

There are electrolyte drinks out there that are very popular and replace lost salt, too.

Another option is effervescent tablets such as the ‘Nuun’ brand – drop one of these in your water bottle and it fizzes up, mixing your required salts in with your water supply.  They come in different flavours and some have added minerals, and caffeine, in with them.  It is worth remembering that when these fizz up, the bubbles and froth can start to drip out of the sipper on your water bottle.  Their synthetic taste isn’t for everyone, and will remain in your water bottle long after you’ve cleaned them out.

When to take salt?  

The simplest way to take your salts is at every check point,  assuming there is one roughly every 10km.  That way, you take the salts at the same time you fill up your water supply, and are less likely to forget about them.

How much to take?  

There’s little science here, and trying to calculate how much salt you lose in sweat and how much you need to replace that can get you in knots – I tend to err on the side of ‘too much salt is better than not enough’, so usually stick to 1 or 2 salt capsules at every 10km check point.  If you are a very slow walker in hot conditions then consider taking more between aid stations.

Thomas Watson

Thomas Watson

Thomas Watson is an ultra-runner, UESCA-certified running coach, and the founder of MarathonHandbook.com. His work has been featured in Runner's World, Livestrong.com, MapMyRun, and many other running publications. He likes running interesting races and good beer. More at his bio.

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