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Does Pre-workout Dehydrate You During Workouts? The Answer

Isaac Robertson
Published by Isaac Robertson | Co-Founder & Chief Editor
Last updated: August 13, 2023
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I remember my college performance coach always drilling the importance of hydration during training, and as a personal fitness trainer, I now do the same for my clients.

One question I often get from clients and readers is whether some pre-workout supplements are causing them increased dehydration during workouts.

To look at this from a scientific point of view, I teamed up with my nutritionist to review the labels of the pre-workouts that we recommend.

And we found some surprising facts that I can share with you.

Quick Summary

  • Some pre-workout supplements can have an impact on your hydration levels, and it's important to see how it impacts you.
  • The one ingredient you need to be careful of is caffeine, and it all comes down to the dose in your pre-workout.
  • There are ways to counteract the dehydration effect so that you don't have to stop taking your favorite pre-workout.

Do Pre-Workouts Cause Dehydration?

Holding a tumbler

Yes, dehydration is one of the side effects of a pre-workout. And it's an effect that a lot of people probably experience at other times of the day as well.

The one ingredient that has some impact on your hydration levels is caffeine.

And because it's such an effective ingredient for improving your performance levels, it's often included in men's pre-workout supplements [1].

However, caffeine also acts as a diuretic, which means that it causes your kidneys to become more active and filter out more water from the body [2].

Over the years, many people interpreted this as being a sign that coffee would cause dehydration. But you need to keep in mind that it mainly causes the release of water from your stomach and not from other parts of the body [3].

What this means is that while you may need to pee more after taking caffeine in a pre-workout, it won't dehydrate your muscles or other organs.

In addition, it might neutralize some of the pre-exercise water intakes, leaving them with less water on hand to deal with sweating in the gym.

The importance of keeping optimum hydration during exercises cannot be overstated.

Dehydration can be reduced and exercise performance can be improved by drinking enough water throughout the day and taking pre-workout supplements.

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"Drinking caffeine-containing beverages as part of a normal lifestyle doesn't cause fluid loss in excess of the volume ingested."

- Katherine Zeratsky, R.D., L.D.

What Other Factors Influence Hydration?

And this is where things get interesting.

First of all, a pre-workout will allow you to train harder, and that will make you sweat more.

And if the temperature at the gym is higher than standard room temperature, then you'll also sweat more.

Then you have to factor in that caffeine is a thermogenic pre-workout, which means that it will slightly raise your body temperature [4].

All this can add up to significantly more sweating than during a normal workout, and you need to consider that additional loss of water weight.

Also, your pre-workout session duration affects your hydration status, along with the intensity of your workout and the environment temperature.

Longer workouts may increase fluid loss through sweat, emphasizing the importance of replenishing fluids before, during, and after exercise.

Water and electrolytes can help offset these factors and support optimal hydration levels during your pre-workout and training sessions.

Tips For Avoiding It

Drinking a water

Here is what I recommend you do if you're heading into a training session with a pre-workout.

First of all, take the pre-workout with about 8-10 ounces of water half an hour before you hit the gym.

This should help provide some hydration, and it's something you should do when you train without supplements too.

Then, take regular sips of water during training to rehydrate while you're sweating. I generally aim for about a pint of water in a training session.

And finally, if you want to be precise, then weigh yourself before and after training.

The difference on the scales will be water weight from sweating, and you should aim to drink at least that amount after exercise.


Do Some Pre-Workouts Make You Retain Water?

Yes, some pre-workouts that contain creatine can make you retain water. Creatine has been shown to make your muscles hold more water. It's a temporary effect but is something to consider when taking it on a regular basis.

How Much Water Should You Drink With Pre-Workouts?

You should drink at least eight ounces of water with pre-workouts. This will help boost your hydration levels before you hit the gym. It will also limit how much water you lose from peeing before you start your workout.

Keep An Eye On Your Hydration Levels

Staying hydrated is a critical part of exercise performance and general health.

And while some pre-workouts can impact your hydration levels, that should be a reason not to take them.

Make sure you drink plenty of water before, during, and after training to make up for any potential loss.

And you could also consider taking a caffeine-free pre-workout to avoid the effect. You'll still need to drink plenty of water to make up for sweating, but it could reduce the potential for losing too much water before you get started.


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