What Is Pre-workout? Does It Work? Is it Safe? Supplements 101

Welcome to a new series, Supplements 101, where I break down the science behind different fitness supplements and help you find what’s right for you!

This week, Pre-Workout 101:

  • What is pre-workout?
  • What is is it made of?
  • Is it actually useful? (A review of scientific papers)
  • Is it safe to consume?

This post will not cover which pre-workout brands are best and what to look for when purchasing, but I’m hoping to continue this series and cover that in a later post, so stay tuned!

What is it?

Pre-workout is a supplement commonly taken shortly before a workout (between 15-60 minutes). It is used to increase focus, energy, and endurance. Sometimes you’ll also find ones that advertise “pump”, which essentially means making your muscles look bigger.

[Pre-workout is sometimes used for improving muscle size/definition at the gym]

Pre-workout is typically sold as a powder that can be mixed with water and consumed as a drink. It is often flavored–coming in options such as watermelon, limeade, or orange mango–to enhance the taste and make it more enjoyable. It can also be purchased as a pill, though that is much less common.

Its effects typically last for a few hours, though they tend to peak earlier on in that time frame.

It is typically taken frequently–often between 3-6 times per week–and in small doses.

What is it made of?

Pre-workout supplements are typically made from some combination of the following ingredients. Not all ingredients listed below are present in every pre-workout mix:

  • Arginine [Semi-essential amino acids]
  • Branch-chain amino acids (BCAAs) [Amino acids]
  • Beta-alanine [Non-essential amino acid]
  • Caffeine [Stimulant]
  • Creatine [Compound derived from amino acids]
  • DMAA [Stimulant]
  • L-citrulline [Non-essential amino acid]
  • Niacin [B vitamin]
  • Phosphorus/phosphates [Element]
  • Taurine [Acid]

In pre-workout supplements, these are often combined as part of a proprietary formula, which means that the sellers do not disclose the exact amounts of each ingredient.

In the United States, sellers must only list which ingredients are included and order them in descending order by quantity. Since most distributors leave details out, is almost impossible with most products to know how much of each substance is being consumed per serving.

This is especially true when considering that even when sellers say how much of an ingredient they include, their claim does not always match reality. For example, a study of pre-workouts in Australia found that only 6 out of 15 nutrition labels included details on caffeine content at all, and in those that did, the actual amount of caffeine ranged anywhere from 59% to 176% of what the packaging claimed!

Is it useful / backed by science?

Although many pre-workout brands tout the impressive effects of their mixes, most of the ingredients aren’t all strongly backed by science. Studies have indicated that many of the ingredients–when taken in proper doses–can benefit individuals with certain health conditions or have generic wellness benefits, but not many studies have conclusively shown benefits for athletic performance.

In fact, of all the ingredients listed above, creatine is the only one with a long history of positive scientific backing for performance enhancing effects. The rest have pretty mixed reviews, with a few studies even showing negative effects–particularly when multiple of the above ingredients are mixed together, as they are in most pre-workout mixes.

Is it safe to take?

Pre-workout is generally considered safe for most people, but there are some significant concerns to be wary of.

1. Lack of Regulation

In the United States, supplements are not regulated by the FDA the same way that food or medications are. Producers are NOT required to disclose the quantities of each ingredient that they include in their mixes. This makes it difficult to know whether you are actually consuming a safe, recommended dose. It can be easy to overdose on an ingredient if you pick the wrong brand.

2. Drug Interactions

Many of the ingredients in pre-workout mixes interact with common medications to produce what can sometimes be dangerous side effects by preventing the drugs from operating properly–and sometimes causing serious reactions.

For example:

  • Arginine (L-arginine) has been known to interact with blood thinners, blood pressure regulators, and diabetes medications
  • Taking DMAA with other stimulants (such as caffeine) can cause increased heart rate and high blood pressure
  • BCAAs can combine with blood sugar medications to cause dangerously low levels

If you take any sort of medication, you should absolutely consult a health professional before taking pre-workout. Given the large number of ingredients, there is anon-negligible chance that one of them could react dangerously with your other drugs.

[Be very careful with pre-workout supplements. They can lead to drug interactions resulting in serious problems like high blood pressure].

3. Side Effects

Although most of the side effects of pre-workout ingredients are relatively mild, they can at times have serious effects.

An otherwise healthy 33 year old woman was admitted to the ER with heart problems after taking pre-workout and a 25 year old man–also with no serious conditions–had a stroke after taking a pre-workout supplement called Animal Rage XL.

Pre-workouts have also generally been known to occasionally cause high blood pressure, heart issues, and gastrointestinal distress.

4. Dangers During Pregnancy

Pre-workouts are especially dangerous to pregnant women, primarily due to their stimulant content.

Stimulants have been shown to lead to premature birth, low birth weight, fetal deformities, and heart problems. Even a daily consumption of as little as half a cup of coffee can lead to lower birth weight, and pre-workouts typically have much higher caffeine concentrations than that.

Pre-workout during pregnancy is very risky and should only be used after thorough consultation with a doctor.

Summary of Ingredients, Uses, Scientific Research, and Safety

To help promote a well-rounded understanding of pre-workout, I’ve created a table summarizing the main categories discussed above: what the ingredients are, their purported benefits, scientific evidence of performance enhancement, and potential side effects.


Pre-workout supplement mix, taken shortly before a gym session, may provide some benefits, however:

  • There is not much scientific evidence to back up its effectiveness
  • Usefulness likely varies dramatically by brand due to differences in ingredient concentrations, and also by individual
  • It can be dangerous for those who are pregnant or who are taking other medications

Do not blindly trust pre-workout supplements you come across. Do your research to find reputable brands–preferably those that tend to have lower doses of stimulants (the more dangerous ingredients) and disclose what they put into their mix. And if you fall into a group at risk of side effects, do not take pre-workout without first consulting with a doctor.

If there’s anything else you’d like me to cover related to pre-workout, or other supplements you’d like to have covered in this series, please share in the comments!

Sources / Learn More

Common Ingredient Profiles of Multi-Ingredient Pre-Workout Supplements

Common Habits, Adverse Events, and Opinions Regarding Pre-Workout Supplement Use Among Regular Consumers

Multi-ingredient pre-workout supplements, safety implications, and performance outcomes: a brief review

The effect of acute pre-workout supplementation on power and strength performance

Effects of Pre-Workout Supplements on Power Maintenance in Lower Body and Upper Body Tasks

Caffeine content of pre-workout supplements commonly used by Australian consumers

Efficacy and safety of ingredients found in preworkout supplements

Impacts of Caffeine during Pregnancy

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