Total Shape is a reader-supported site. Purchases made through links may earn a commission. Learn more.

Can Pre-Workout Cause Stomach Problems? (From a Doctor)

Michael Garrico
Published by Michael Garrico | Co-Founder & Marketing Director
Last updated: September 3, 2023
We personally test every product featured in our reviews and guides. By ordering products anonymously and getting a group of independent testers, we are able to get first-hand experience and provide data-driven recommendations. Learn more.

As a personal fitness coach, I spend many hours a week working with clients at the gym and guiding them toward their fitness goals. Their exercise routine is only part of their plan; we also discuss their food habits and dietary supplements.

Pre-workout supplements are popular for many gym-goers to boost energy, endurance, and recovery, but some experience stomach issues and wonder if their pre-workout is the culprit.

I consulted our medical professional and looked in-depth at common ingredients found in pre-workout supplements to determine if they could cause stomach problems.

Here’s what I found.

Quick Summary

  • Pre-workouts can cause stomach problems as it contains certain ingredients like magnesium, caffeine, sodium bicarbonate, and caffeine.
  • Diarrhea, bloating, and stomach upset are some of the stomach problems you risk suffering.
  • Pre-workouts may also reduce fatigue, promote muscle growth, and increase endurance.

Can Your Pre-Workout Be Causing Stomach Problems?

A person holding his stomach with red graphics around the area

Your pre-workout can cause stomach problems if it contains certain ingredients common in many pre-workout supplements, like magnesium, sodium bicarbonate, caffeine, and creatine.


Magnesium, a common addition to pre-workout supplements, is an essential mineral playing a vital role in energy metabolism and muscle function [1].

Adverse effects of magnesium as a pre-workout, particularly magnesium citrate supplementation, include diarrhea, stomach cramping, and nausea [2].

Sodium Bicarbonate

Sodium bicarbonate, also known as baking soda, may enhance exercise performance [3].

However, baking soda as a pre-workout can cause nausea, vomiting, stomach cramps, and loss of appetite, but this generally occurs only when taken at high doses [4].


Look at the label on your pre-workout supplement, and you will likely see caffeine. Being a central nervous system stimulant, caffeine boosts energy, performance, and fat burning [5].

Gastrointestinal side effects of caffeine include acid reflux, stomach upset, abdominal pain, or diarrhea which can lead to dehydration [6].


Creatine is as popular as caffeine as an ingredient in pre-workout supplements because it can be highly effective at improving athletic performance and endurance, as well as promoting muscle recovery [7].

The most frequent negative effects of creatine supplementation are stomach upset and diarrhea [8].


L-arginine, an amino acid precursor to nitric oxide, is added to pre-workouts to increase nitric oxide levels and boost pumps [9].

L-arginine supplementation can have a negative impact on the gastrointestinal system by causing bloating, diarrhea, abdominal pain, and nausea [10].

“Caffeine is a fairly safe supplement at the recommended doses. It may cause minor side effects in some people and should be used with caution in individuals with heart disease, high blood pressure, GERD, and several other conditions.”

- Rudy Mawer, MSC, CISSN

How to Reduce Stomach Issues

A woman stretching on the ground

Exercise is essential to physical health and to combat stress, anxiety, and depression [11].

Any adverse effects from pre-workouts like stomach upset, bloating, and diarrhea can inhibit your ability to work out, which can be detrimental to your physical and mental health.

I usually tell my clients a few things they can do to reduce gastrointestinal issues caused by pre-workouts:

  • First and foremost, consult your doctor to discuss any adverse reactions or underlying medical conditions before starting any new supplement.  Additionally, avoid proprietary blends which lack transparency about ingredients and dosage. Knowing precisely what you are consuming is critical to putting your mind at ease concerning any health risks.
  • Follow the manufacturer’s directions when mixing your pre-workout supplement. Not using enough water and consuming a concentrated liquid can lead to an upset stomach and diarrhea [12].
  • When it comes to label reading, look for independent lab testing stamps that will validate the quality of the product. Some examples of separate testing facilities are NSF International,, and USP.
  • Be aware of any ingredients that affect you negatively, and avoid them. For example, if you are sensitive to caffeine, plenty of caffeine-free pre-workouts are available.

Other Side Effects

A woman working out in the gym looking at her arm

Digestive system issues are not the only side effects of pre-workout intake.

After consumption, some people experience pre-workout tingles due to the addition of beta-alanine and amino acid that reduces acidity in muscle tissue.

Beta-alanine helps reduce fatigue, increase endurance, and promote muscle growth [13].

Though not harmful, this tingling sensation is bothersome to many individuals.

Many of my clients believe their pre-workout supplement hinders their weight loss efforts, but It is not uncommon for the top pre-workouts that contain creatine to cause water retention [14].

I remind them that the number on the scale likely reflects water weight, not body weight gain.

Many pre-workout supplements contain a lot of caffeine, which, when consumed on top of your daily coffee or soda consumption, can put you above the daily recommended caffeine dosage of 400 mg.

Besides stomach problems, caffeine can cause increased blood pressure, possibly leading to heart palpitations and even an increased risk of a heart attack [15]. 

Some users experience pre-workout itching or burning sensation of the skin, likely due to the addition of niacin (B3), which increases blood flow, causing a rush of blood to the skin's surface, and resulting in skin flushing [16].

Related Articles:


Can Pre-Workouts Affect IBS?

Yes, pre-workouts can affect IBS and trigger symptoms. Many people with IBS follow a low FODMAP diet. FODMAPs are a group of compounds believed to trigger IBS and other digestive problems.

Some pre-workout ingredients, like artificial sweeteners, are considered high FODMAP.

Should I Take Pre-Workout on an Empty Stomach?

Yes, pre-workout on an empty stomach allows it to enter the bloodstream much quicker, so you feel the effects quicker.

On the flip side, you may have an increased risk of digestive issues when taking on an empty stomach.

So, Is Your Pre-Workout Supplement Causing Stomach Problems?

Your supplement may be causing some unpleasant side effects, but that doesn’t mean there isn’t one that will work for you.

Reading labels, being aware of how certain ingredients affect your body, and following the manufacturer’s instructions are all key to reducing potential adverse effects.

We know finding the right supplement is tricky, which is why we have tested and reviewed dozens of products:

These are our lists of best, all-natural, high-quality pre-workout supplements for both men and women. Take a closer look to find out our #1 pick.


Was this article helpful?

About The Author

You May Also Like

Write a Reply or Comment

Your email address will not be published. Required fields are marked *