What are the Side-Effects of Pre-Workout Supplements? (and How to Avoid Them)

Pre-workouts are one of the most popular supplements for helping people improve workout performance.

A study published by ISSN, the International Society of Sports Nutrition, found that 30% of people take pre-workout supplements as part of their exercise and nutrition routine.

But like any supplement, there can be side-effects, especially for those who have sensitivities to ingredients used in pre-workouts.

The most common pre-workout side-effects include skin reactions, nausea, heart abnormalities, and light-headedness and dizziness.

In this article, we will look at the rising popularity of dietary supplements like pre-workouts and discuss the most common adverse reactions from using them.

Let’s jump in.

The Rising Trend of Pre-Workout Supplements

The use of dietary supplements to boost exercise performance has become a common practice among fitness-conscious individuals and athletes.

In the United States, as of 2012, more than half of adults reported regular dietary supplement use (Kantor et al., 2016). This trend has almost certainly continued to grow, given the ever-increasing economic impact of the dietary supplement industry, estimated at $122 billion in 2016 and projected to reach nearly $278 billion by 2024.

As mentioned at the top, pre-workouts are a big piece of the supplement industry, with 30% of young adults using them to boost their workouts.

Considering its popularity, its also important to be aware of possible side-effects of supplementing with pre-workouts.

In a study titled, “Common Habits, Adverse Events, and Opinions Regarding Pre-Workout Supplement Use Among Regular Consumers,” researchers surveyed 746 healthy young men and women regularly consumed pre-workout supplements.

Over half (54%) reported experiencing side-effects, including skin reactions, heart abnormalities, nausea, and feeling light-headed.

Next, we will look at each pre-workout adverse reaction in more detail, how different types of pre-workouts can make adverse reactions worse, and offer some suggestions for choosing a formula that can reduce the severity of the side-effects.

Let’s jump in.

The Side Effects of Pre-Workouts

The main side effects of pre-workouts include skin reactions, nausea, rapid heart rate and palpitations, and dizziness or light-headedness.

Skin reactions

According to a study published in the medical journal Nutrients, which examined the most common adverse reactions to using pre-workout supplements, or multi-ingredient pre-workout supplements (MIPS), the most frequently cited side-effect was skin reactions.

Face flushing, skin tingling, and skin itch are common side-effects of using pre-workouts. They are caused by beta-alanine, an amino acid, and niacin, also known as vitamin B3.

This tingling and flushing of the skin, known as paresthesia, is not harm and is temporary, typically subsiding within 30 minutes of ingestion.

For users who don’t like this feeling, consider a pre-workout without beta-alanine.

Although beta-alanine is commonly found in pre-workouts, there are plenty of brands and formulas that give athletes and gymgoers the same energy boost and increased workout performance without the skin reactions.

Nausea

According to the study mentioned earlier, the second more prevalent adverse reaction to supplementing with pre-workouts is nausea. A whopping 25.6% of the 746 respondents in the study experienced nausea after taking a pre-workout.

There are several reasons why pre-workouts can cause nausea. For starters, some pre-workouts have very high caffeine dosages, with some as high as 425mg per serving.

Standard pre-workouts have caffeine content of 100-200mg per dose, while no-stim pre-workouts have zero caffeine. There are also a selection of low-stim (50-75mg of caffeine per dose) pre-workouts who can tolerate a little caffeine.

While taking pre-workout on an empty stomach can help speed up absorption, it can also increase the likelihood of nausea as there is no food to act as a buffer. Pairing a pre-workout with a light snack like a banana can help mitigate some of the nausea.

Heart abnormalities

Pre-workouts are essentially stimulants, and with stimulants comes increased heart rate and blood pressure can feel unnerving and uncomfortable.

Jagim et al., 2019, found that heart abnormalities to be the third most prevalent adverse reaction to pre-workout supplements. Rapid heart rate and even heart palpitations happened at least once to 23.4% of people who had taken a pre-workout.

High doses of caffeine have been shown to cause a significant number of cardiac comorbidities, including palpitations and several types of heart arrhythmias (Wassef et al., 2017). Caffeinated beverages have also been shown to elevate blood pressure in young healthy males (Grasser et al., 2015).

Pre-workouts have between 100-200mg of caffeine per serving, which when paired with external caffeine ingestion (from coffee, tea, energy drinks, and so on) can cause abnormally high heart rates.

Consider also that caffeine has a half-life of 3-7 hours, so that morning coffee could very well be cascading caffeine into your afternoon pre-workout.

Monitor your caffeine intake over the course of the day, avoid pre-workouts with high caffeine dosages, or choose a low or no-stim pre-workout to reduce the likelihood of heart abnormalities.

Light headedness and dizziness

Pre-workouts, and the caffeine content within each dose, can also cause light headedness and dizziness in people who have a sensitivity to caffeine or people who take pre-workouts on an empty stomach.

As we discussed earlier, caffeine is a stimulant that makes your heart beat faster (which promotes blood flow to target muscles and sharpens focus) and affects the body’s ability to produce adenosine, which reduces cerebral blood flow.

This pre-workout side-effect can be the result of a sensitivity as well as simply taking too much caffeine.

Per the United States Department of Agriculture and the European Food Safety Authority, healthy adults should limit daily caffeine consumption to 400mg (Belayneh and Molla, 2020).

Why do pre-workouts make me go to the bathroom?

Pre-workouts can sometimes lead to an upset stomach, bloating, and diarrhea.

Pre-workouts often use sodium bicarbonate, also known as baking soda, which can cause gastrointestinal discomfort at levels of 0.3g/kg (Grgic et al., 2021).

Creatine monohydrate, an ingredient commonly used in pre-workouts, can cause diarrhea, especially in higher doses (Ostojic and Ahmetovic, 2008). Higher intakes of caffeine are also linked to diarrhea (Belayneh and Molla, 2020).

Other ingredients commonly used in pre-workouts, such as and caffeine, can sometimes cause stomach upset leading to quick trips to the rest room after polishing off your shaker cup.

Wrapping Things Up

Pre-workout supplements can be an effective tool for experienced athletes and gymgoers looking to get more from their workouts.

The popularity of pre-workouts is understandable thanks to the flood of energy you experience after ingesting them.

That said, adverse reactions are common, including skin irritation or tingling, rapid heart rate, and light-headedness.

These effects are so common, in fact, that there are numerous pre-workouts on the market that help you avoid dosages and ingredients that cause adverse reactions.

Choose a pre-workout that matches up with the way your body reacts optimally, and you can get the best of both worlds: better workouts and minimized chances of side effects.