Hydration - How much fluid should you drink while hiking?

My usual advice for dehydration in The Lake District is open your mouth and tilt your head skywards. But this weekend it's actually going to be rain free and warm and, for once, there may be a danger of dehydration. So I've included a few dehydration pointers to help you out.
But first some scary statisticsBut first some scary statistics
5% dehydration decreases you physical performance by as much as 30%. At 7% loss you are at serious risk of fatal heat stroke - with cramps, fatigue, vomiting, coma and death to look forward to.

This is even scarier when you realise you can lose 2% of your body weight through dehydration in just one hour. Just a few hours in hot weather can cause a lot of damage. Now that your scared it would be great to have a link to our 'Sports drinks' page, but we haven't got one…damn
How to avoid vomiting, coma and death
Try going belly up in your garden under an umbrella with a cool hydrating liquid of your choice. That's one solution, for the more adventurous, here's a few tips to keep you from vomiting, coma and death.

In a life of stating the obvious, here's the most obvious thing I've ever said, 'if you want to stay hydrated don't get thirsty.' Before you shut down the page and never return to our website, wait, there is a reason for saying this. Your thirst mechanism lags behind your actual level of dehydration. So when you feel thirsty you're already dehydrated. Also, when you sneak behind that granite outcrop for a private moment, keep an eye on your wee wee. One, so it doesn't go down your leg and two to check the colour. If it's darker than a straw colour you need to get some liquid into you.

How to avoid vomiting, coma and death
Prehydrate - this probably isn't a real word but it sounds good
If you're going hiking all day tomorrow, have a little bit more water than you would normally have today. I'm not saying wet the bed, but just begin your hike hydrated and that's a good start. Then all you need to do it top up during your day on the fells. At the very least drink 0.5L of water a couple of hours before you set off and leave another 0.5L in the glove box for when you come back.

Also, sprinkle a little more salt on your chips the day before so your sodium levels are okay for the next day.

While you're hiking While you're hiking
I've checked round dozens of authoritative websites and most of the hydration experts say on a hot day you should be drinking 0.5L to 1L of water per hour. If you're hydrated before you begin then you might get away with 0.5L per hour but if not and it's hot then definitely 1L.

Another general rule, almost as obvious as the don't get thirsty one is: if you're sweating then drink more.

If you hiking for 8 hours on a hot day it would be a nightmare to carry 8L of water, so in this case always prehydrate, carry 3L of fluid and maybe a water purification tablets or device so that you can top up along the way. When you get down from the mountain keep drinking.

How should you drink?
Yep, through your mouth, you tend to absorb less through your ear drums… Okay, that was just being stupid. Drinking little and often - every 15 minutes - means fluid is absorbed faster. Hydration systems are ideal for this. Glugging back a litre in one go isn't good for the absorption process and you'll end up weeing a lot of it back out.
What should you drink?
For short walks water is just fine, but if you're out a bit longer you could do with supplementing your water intake with a sports drink. Isotonic sports drinks are the best and the choice of athletes, so if it's good enough for Phil 'The Power' Taylor it's good enough for me.

Isotonic drinks quickly replace fluids and have a glucose concentration of 6 - 8%, the glucose helps fluid retention and delays fatigue. A few of the best ones are Lucozade Sport, Boots Isotonic, High Five or you could make your own:

200ml of concentrated orange squash, 1 litre of water, pinch of salt all mixed up should do the trick.

What should you drink?
Cold Fluids
Cold fluids empty from the stomach quickly and are therefore absorbed faster, so if you're really fanatical you could freeze your hydration bladder the night before so it stays cool for a good part of the next day.

Fruit juices aren't very good. They are generally 10% sugar which is too sugary. Juice sugar is fructose which is harder for the stomach to digest than glucose. The sugar sits in the gut attracting water out of the tissues - exactly the opposite of what you want to happen.
If you can't be bothered reading the rest, here's a summary
Don't get thirsty or wee on your pants, prehydrate, drink little and often through your mouth not your ear drums, take water and a isotonic sports drink on long walks, sprinkle some salt on your chips, have a little bit extra if you're sweating buckets or forget it and lie in the garden. Hope that clears things up.

Thanks for reading.

Ian Young

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