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6 Side Effects of Pre Workout (2022 Upd.) How to Avoid Them

Isaac Robertson
Published by Isaac Robertson
Fact checked by Donald Christman, BHSc FACT CHECKED
Last updated: February 3, 2022

This is a question I often get asked by friends and clients, and it often comes from the point of view that many people associate these products with slightly shady or illegal performance enhancers.

However, nothing could be further from the truth, and the products I recommend are all based on natural ingredients. But that doesn’t mean there are no side effects or bad products out there.

Beyond avoiding a poor quality supplement that may not agree with you, there are a few side effects that are both common and likely.

While the supplement industry has done it’s best to reduce these as much as possible, you still have to be aware of them.

From my own experience and through countless conversations with dieticians and nutritionists, I have compiled a list of ways your body might react and how to deal with those situations.

First, though, let’s take a look at what’s in this stuff.

What Is In Pre-Workout Supplements?

white powder filling a silver spoon

Essentially, you will usually find a handful of ingredients in all the top pre-workout products which include creatine, caffeine, citrulline, branched chain amino acids (BCAA), and beta-alanine to name just a few.

While the blend and amount of the different nutritional boosters will vary, the main purpose is to give you a boost of energy to give you more strength and endurance during a workout session.

In most cases, they are powders that you mix into a drink, and you simply take it about 15 minutes before you start training.

There are literally dozens of products available, and it can be quite a challenge to figure out which ones will work best and have the least side effects. We have several recommendations on this site that you should definitely check out.

My Bonus tip is always to check the label, and if you see something hinting at “proprietary blend,” then generally avoid it.

Unless it comes highly recommended from someone you trust, there are enough options with no hidden blends available.

The pre-workout you consume can also be tailored to improve a variety of factors such as endurance, strength, or muscle growth.

- Peter Tzemis, Bachelor of Health Science

What Does Pre Workout Do?

man flexing his bicep muscles

Basically, the whole idea behind taking a pre-workout supplement is to increase energy levels to help you perform better during your exercise and training. (1)

This might sound like some illicit form of doping, but the products you can buy off the shelf are completely legal and contain only natural substances.

You’re not going to suddenly perform like the Incredible Hulk, but a performance boost of 10 to 25% is very achievable. And this will help your body to build more muscle while at the same time helping with weight loss.

Let’s take a look at some common ingredients.

Pre-Workouts With Creatine

Creatine is one of the most sought after ingredients for a very good reason. Every cell in your body needs creatine in order to produce energy. (2)

When your muscles receive a boost of this substance, they will have more energy to help increase strength and stamina for maximum pumps.

One study, in particular, noted that there were very large performance increases (over 15%) in resistance training using weights.

This performance boost will help to build muscles faster while at the same time burning through more fat. Basically, a double boost to your health.

However, some people prefer pre-workouts without creatine as they don't want the side effects that come with it.

Pre-Workouts With Caffeine


Caffeine is one of those stimulants that had been completely underrated for decades. These days, however, you’ll probably struggle to find a supplement that doesn’t contain it.

On average, I have found that the amount of caffeine is usually in the range of 1 to 2 regular 8-ounce cups of coffee. It’s not huge, but you want to keep this in mind if you’re a coffee drinker to avoid the jitters.

The health benefits come in two distinct ways.

First of all, studies have shown that caffeine boosts thermogenesis which basically is a fancy way of saying that your metabolism increases body heat by burning more energy. (3)

Secondly, it has been proven to boost mental and physical endurance by up to 12%. So, you can work harder and burn more fat.

The most prevalent ingredient in pre-workout supplements is caffeine. Typical supplements can contain anywhere from 100 to 300 mg of caffeine, which is up to three times the amount in a cup of coffee.

- Kay Ireland, Certified Group Fitness Instructor

Other Pre-Workout Ingredients And Their Benefits

While caffeine and creatine are the two most common ingredients, there are several others that you can find on the labels of dietary supplements.

A lot of these have very fancy names that most people don’t really understand. So let me try and help you out and show you how these can improve results in your training and fitness goals.

1. Citrulline

This amino acid is produced by your body and is vital for increasing blood flow. However, your body can only produce so much of it naturally.

By getting a boost before you start training, you can heighten blood flow and supply more oxygen and nutrients to your muscles.

One study found a significant correlation between endurance and Citrulline in performance athletes.

2. BCAAs

The fancy science name is branched-chain amino acids, and there will be no rewards for remembering it; just call it BCAA.

Essentially they are types of protein that the body cannot produce, meaning they have to be taken in with food.

While they have only a minor impact on muscle building, one study found that endurance improved in athletes taking BCAA.

Related: Is BCAA Good as Pre-Workout?

3. Sodium Bicarbonate

Yes, that’s basically the same as your household baking soda. While study results have been mixed, there is at least some evidence that it works as a buffer to reduce the buildup of acid.

If it does indeed reduce the amount of lactic acid in muscles, then it could well be an excellent ingredient.

Because it’s both cheap and safe to take, there’s nothing wrong with taking a chance on it.

4. L-theanine

The final ingredient that I like to see in the products I use and recommend is L-theanine, especially when it’s combined with caffeine.

One study has shown that it can significantly enhance your ability to stay focused. (4) This is beneficial both in the gym and at work or during study times.

Now that you’ve learned about some of the substances you might find let’s see what the negative effects can be.

Possible Pre-Workout Side Effects

First, let me say that most people that I talk to that had negative side effects usually had some allergy or food intolerance to the ingredients. That’s why you should always check the labels to see if there’s anything in it that you know causes you some upsets.

That being said, there are a few things that you can encounter, and you should pay close attention to how your body reacts:

  • Insomnia can happen if you’re a coffee drinker and take your supplement late in the evening
  • Diarrhea is less likely, but the combination of caffeine, sodium bicarbonate, and creatine can have a laxative effect.
  • Headaches and jitters can occur with high caffeine doses.

Before you panic about these, there are some simple steps you can take to avoid them altogether.

6 Ways to Prevent Negative Pre-Workout Side Effects

1. Insomnia

A yawning exhausted woman

Caffeine impacts people very differently. I often see people in Starbucks at 9 pm, and I wonder how they could possibly be getting any sleep.

Personally, I avoid coffee after 6 pm and on the days where I hit the gym later in the day, I avoid it in the afternoon altogether.

If you know that coffee does affect your sleep, then it’s best to take it no later than 7 pm or choose a pre-workout that is caffeine-free. There are some excellent options available, and I cover a few of them in the reviews section.

2. Diarrhea

woman feeing pain

Yes, that awful feeling where you just cannot bear to be more than 10 paces from a toilet is one of the more disruptive effects. However, in most cases, this is due to food intolerance, and in the rare circumstances that it happens, there is a simple solution.

First of all, pre workout on an empty stomach is not a great idea, especially after fasting. Get at least a little bit of food into you first.

Secondly, reduce the dose to half the amount to start off with. It might just take your stomach a few days to get used to it.

3. Dehydration

pitcher glass pouring water in a glass cup

You might find that you feel a lot thirstier than normal when you’re exercising and this can be due to the combination of substances in your chosen supplement.

Some are specifically designed to help you tap into glycogen reserves which is an energy resource that binds directly to water.

My main tip here is not to wait until you feel thirsty and your mouth is dry. This is actually a more advanced stage of dehydration and will have a significant impact on your performance.

So, make sure you drink plenty of water throughout the day and take constant sips while you’re training.

4. Headaches

These are mostly associated with high caffeine doses and dehydration. Some ingredients are added to boost your blood flow, and they do this by expanding blood vessels. Some people are sensitive to this effect in the brain.

It is less common for these products to trigger migraines, but if you do find that you’re consistently suffering from headaches, then you should stop taking the supplement for a few days.

You can then start with a smaller amount, and it’s always best to take a few extra cups of water.

5. High Blood Pressure

One of the effects of all stimulants is an increase in your heart rate, and this can also cause high BP. If you have issues with your BP anyway, then it’s probably best to avoid these stimulating substances altogether.

It’s important to check your BP before and after working out. If it’s significantly elevated at these times, then start by choosing a caffeine-free product.

Just take your supplement in moderation and you'll do just fine.

6. Tingling Sensations

human skin having a goosebumps

Some people are more sensitive to certain ingredients like beta-alanine or vitamin B3, and as these directly impact the nervous system, there is a chance that you’ll feel some tingling throughout your body after taking a pre-workout.

It’s perfectly normal and usually only lasts a short while. When this does happen to me, I find it more distracting than problematic, but I’ve become used to it and just ignore it.

Once you start training it usually goes away pretty quickly.

So, you have a few tips to avoid negative effects, and the last question to address is: when to take pre workout for minimum negative effects?

I generally recommend not taking it first thing in the morning, and no later than 7pm. If you stick with that, then you’ll avoid pretty much all unpleasant feelings.



1. Can You Take Too Much Pre Workout?

Yes, you can take too much pre workout which can leave you feeling unwell and jittery. The main reason for this is that too many stimulants like caffeine will increase your heart rate, cause stomach discomfort and a lack of mental focus.

2. Can You Take Pre-Workout On An Empty Stomach?

Yes, you can take pre-workout on an empty stomach, but some people might encounter stomach upset and even diarrhea. The advantage is that it’s absorbed very quickly, but I generally recommend at least a small snack before you take it.

3. Can Pre-Workout Cause Kidney Failure?

Pre-workout can only cause kidney failure if taken in excessive amounts while ignoring negative side effects. Some ingredients cause high blood pressure and dehydration which can negatively impact your kidneys. But actual failure is highly unlikely and would require sustained high doses.

4. Is Pre Workout Bad For Your Heart?

Yes, pre-workout can be bad for your heart if you take it in very large doses or you have an underlying heart condition. Both caffeine and creatine increase the heart rate and blood pressure, but as long as you stick to the recommended amounts and don’t have known issues, then you should be just fine.

5. Does Pre-Workout Make You Fat?

No, pre-workout doesn’t make you fat, but it can increase your body weight. The reason for this is that muscle weighs more than fat, and as your body burns through more fat and produces more muscle, you might actually notice a weight increase. It’s more important to look at your BMI in these situations, than just what the scales are saying.

6. Is Pre-Workout Addictive?

No, pre-workout isn’t addictive, even though some people say that caffeine has some addictive properties. You might feel like you become dependent on it for maximum performance, but there are no studies confirming that any of the ingredients are addictive.

7. Can Pre-Workout Cause Or Worsen Depression?

Generally speaking, pre-workout does not cause or worsen depression. But there are some products out there that contain ingredients that have been tied to depression. Look out for artificial sweeteners like Aspartame or a substance called Dimethylamylamine (DMAA) and avoid them if you have mental health concerns.

Related Post: Does Pre-Workout Go Bad?

Do Pre-Workouts Work?

Yes, pre-workout supplements do work, and there are many studies to back up the reason for including certain ingredients.

Top performance and professional athletes take these products on a consistent basis because of the benefits they provide.

At the same time, you have to be aware of the negative effects so that you can look out for them and take immediate action.

If you’re still wondering: Should I take pre-workout supplements?

The answer is yes, as long as you monitor the side effects and take actions to reduce them.

Hopefully, the above tips will help you so that you can avoid most issues and if you have some more tips to add, then please leave a comment on our Facebook page.


  1. Tia Ghose, Senior Writer, The Truth about Pre-Workout Supplements, retrieved from
  2. Rudy Mawer, MSc, CISSN, How Creatine Helps You Gain Muscle and Strength, retrieved from
  3. Astrup A, Toubro S, Cannon S, Hein P, Breum L, Madsen J., Caffeine: a double-blind, placebo-controlled study of its thermogenic, metabolic, and cardiovascular effects in healthy volunteers., retrieved from
  4. Michael J Breus Ph.D., What You Need to Know About L-theanine, retrieved from


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