The Weight, Urine, Thirst (WUT) system is an ideal tool for monitoring your hydration status and provides an idea of how dehydrated you might be, so we've detailed how to use the system in order to help ensure you're optimally hydrated...

Dehydration and performance

You've probably heard that if you get more than 2% dehydrated you'll start to see a drop off in your performance?

Well, recent research suggests that many athletes can tolerate a higher level of dehydration than once thought and that aiming to replace all of your sweat losses during exercise is certainly unnecessary (and potentially even counter-productive).

That said, you're probably here because you've been suffering with hydration-related issues and want to get a better handle on your hydration status so you can get on top of it?

Here's the thing:

Without the use of radioactive isotopes or taking blood samples it's essentially impossible to know exactly how (de)hydrated you are. But, there's good news...

The Weight, Urine, Thirst (WUT) System for monitoring hydration status

There are 3 things you can monitor together in the ‘real world’ to give you a good enough estimate of your hydration status:

  1. Your body weight
  2. The colour of your pee
  3. Your thirst level

On their own these 3 things can't tell you how hydrated you are as there are factors other than your hydration status that influence them. Read this blog to understand why you can't just rely on the colour of your pee to tell if you're dehydrated, for example.

But some clever people in the US Army decided to combine all three metrics to produce a more reliable hydration rating scale called "the WUT system".

WUT System = Weight, Urine, Thirst System.

Their suggestion is to monitor your body weight, the colour of your pee and how thirsty you are first thing each morning.

The ‘first thing in the morning’ bit is important as it limits the influence of other things that interfere with your hydration status as your day goes on.

You then use the results to give you an of how likely it is that you're dehydrated.

Collecting the data

The data you need to collect each morning is:

  1. Your body weight. Ideally as soon as you get out of bed, before eating, drinking or going to the bathroom. Has your bodyweight fallen by >2% from your normal weight? +1 point if Yes. This spreadsheet can help you collect the data and you can also use it to calculate your sweat rate.
  2. The colour of your pee. Is it light or dark in colour? +1 point if Dark.
  3. Your thirst level. Are you thirsty? +1 point if Yes.

Understanding the results

Score = 0-1? 

It's unlikely that you're dehydrated.

Score = 2?

It's likely that you're somewhat dehydrated. This might impact your fluid intake and training plans for the day, especially if you're planning intense exercise.

Score = 3? 

It's very likely that you're dehydrated and you should strongly consider  correcting that before you do any strenuous exercise involving large sweat losses.

In the long run, tracking this data helps you learn to listen to your body and fine tune your perception of your hydration status and this makes it more likely that you'll be able to stay well hydrated and able to perform at your best when training and competing.

How can you avoid getting dehydrated?

Because that's what you really want to know, right?

Ok, here's something to think about:

The role sodium plays in your body retaining fluid in your quest to stay hydrated.

Sodium helps you retain fluid in your bloodstream, especially useful when your sweat output is high.

Studies such as this recent one by researchers in Spain looked at fluid and sodium intake during a hot 70.3 Ironman event in 2015. Their data showed that athletes who took in more sodium tended to lose less bodyweight in percentage terms than a control group who only took a placebo. 

The group that took the sodium in (and so maintained a better hydration status) outperformed those taking the placebo by an average of 26 minutes in the race.

Yes, you read that right, 26 minutes!

There seemed to be a clear and positive correlation between losing less bodyweight overall (by using sodium supplementation to absorb and retain more fluid) and increased performance.

Want to experiment with your electrolyte/sodium intake? Here's what to do:

  1. Get an idea of how much you’re sweating. i.e. your sweat rate.
  2. Get an idea of how salty your sweat is.


  1. Take our free Fuel & Hydration Planner to help you understand what kind of fluid and electrolyte intake might work for you.

This can then be refined through some good ol’ fashioned trial and error in training.

Or, if you want to know exactly how much sodium you’re losing in your sweat so you can more accurately replace a decent % of what you’re losing, it’s worth considering taking our Sweat Test.

Further Reading