What Does Preworkout Do? Here’s What You Should Know Before Trying These Supplements

If you're an athlete or a fitness pro, you've probably tried many strategies to get ahead of the game. And you've likely heard about preworkout. The popular supplement is believed to boost energy and enhance performance.

Some preworkout supplements may be effective, but the evidence isn't conclusive. There are also safety concerns because the FDA doesn't closely regulate sports supplements. So, there are important considerations before you try preworkout supplements.

What is preworkout?

Preworkout is one of many supplements designed to enhance athletic performance. As a group, these supplements are called multi-ingredient preworkout supplements or MIPS. There are many different types, each with different claims on ways to boost performance. Common ingredients include caffeine, creatine, and amino acids.

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As the name suggests, people take preworkout supplements before exercise or sport. They do this to boost energy levels, improve strength and endurance, and increase focus. Some supplements are geared toward building muscle, for example, while others might aim to stave off fatigue during a workout. The popular supplements come in various forms, including pills, powder, and liquids.

What is in preworkout supplements?

Preworkout supplements have ingredients that may vary by brand. But you'll find some similar key ingredients in many preworkout supplements, such as:

• Caffeine: Caffeine is the most widely used stimulant in the world. And it's a key ingredient in preworkout supplements. It activates the central nervous system. And it may boost energy, increase focus, and enhance athletic performance. Caffeine can also help raise exercise metabolism and support muscle function.

• Beta-alanine: Your liver makes this amino acid. You can also find it in foods like chicken and beef. Beta-alanine has been linked to less muscle fatigue and better exercise performance.

• Creatine: Creatine is an amino acid created in the liver, kidneys, and pancreas. Like beta-alanine, it’s also found in animal foods. Your muscles store creatine and use it for energy. It's been shown to enhance performance, especially during high-intensity, short-duration activities like powerlifting.

• Citrulline: This amino acid helps the body make nitric oxide, a gas that promotes blood flow by relaxing blood vessels. This may help deliver oxygen and nutrients to your muscles, which could boost performance. But, research is still mixed.

• Electrolytes: These minerals help regulate many processes in your body. They also support healthy muscle function. Examples include sodium, potassium, phosphorus, calcium, chloride, and magnesium. You lose electrolyte minerals through sweat. So, it's important to replace them during long bouts of intense exercise.

• Glucose: Glucose, or sugar, is a carbohydrate and the body’s preferred energy source. You need adequate amounts of easily digested carbohydrates for energy before a workout. You’ll also need them during your workout if you exercise for longer than 60 minutes.

• Branched chain amino acids (BCAAs): The amino acids leucine, isoleucine, and valine help regulate muscle protein metabolism. Early rodent studies suggested BCAA supplementation could help muscle building, and it’s still commonly used today. 

Preworkout supplements may contain many other ingredients. These include betaine, B vitamins, carnitine, taurine, tyrosine, and yohimbe. 

Are preworkout supplements effective?

A supplement is only as effective as its ingredients. And preworkout supplement ingredients can vary widely. So, it's impossible to say that all preworkout supplements are effective or ineffective. But some of the common ingredients in many preworkout supplements may be beneficial.

One study looked at how a preworkout supplement affected performance during high-intensity interval training. It led to better aerobic capacity (VO2max), endurance (critical velocity), and training volume.

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The supplement also helped maintain or improve body composition during intense training. A 2018 review found that preworkout supplements enhanced muscular endurance and mood during a workout.

But reviews of scientific literature haven’t been able to support some claims. For example, most studies don’t show that BCAA helps build muscle. Similarly, studies are unable to find a consistent effect on performance from preworkout supplements. 

Ultimately, certain preworkout supplements may be effective. But it depends on several factors, including the key ingredients, proper usage, and your fitness goals.

Is preworkout bad for you? 

It’s unclear whether preworkout is bad for you. The 2018 review that assessed multi-ingredient preworkout supplements found that they’re generally safe. But it also recognized that most studies are short, so there’s a need for long-term data. 

There are known risks involved in taking preworkout supplements that include:

• Not FDA-approved: The FDA doesn't approve the safety and efficacy of supplement ingredients or the ingredient amounts listed on the labels. So, you can't be sure about what's in your supplement as labels may be inaccurate.

• High caffeine content: The caffeine content in preworkout supplements varies. Some products may contain as much as 387 mg per serving. That's equivalent to 2 to 4 cups of regular brewed coffee, depending on the strength. Too much caffeine may cause side effects, such as overstimulation (including restlessness or shakiness), anxiety, dehydration, headaches, high blood pressure or fast heart rate, fatigue, insomnia, and dependence.

• Energy crash: Some preworkout supplements have high amounts of caffeine and sugar, which can lead to an energy crash and related symptoms. Your body metabolizes caffeine and sugar quickly. Both ingredients can give you an initial energy boost followed by a sharp drop when they leave your system.

• Kidney and liver function: Although the research is mixed, some studies suggest that preworkout supplements can impair kidney and liver function.

• Ingredients to avoid: Athletes should also be cautious. Preworkout supplements often contain steroids and other ingredients banned by sports organizations. This could result in a failed drug test and disqualification or loss of employment.

• Serious events: Although rare, preworkout supplements have been linked to cases of pancreatitis and stroke. 

Do you need preworkout supplements?

No, preworkout isn't necessary for most people. A balanced diet can give you all the nutrients you need to crush your workouts. If you’re a competitive athlete or bodybuilder, you may find that a carefully chosen preworkout supplement can help give you an edge.

Talk with your healthcare professional before taking a preworkout supplement. This is particularly important if you have underlying health conditions or take medications.

And never try a new supplement on game or race day since you don't know how your body will react. It’s best to start with small amounts of a preworkout supplement during training. Then, gradually raise the amount when you know how it affects you.

Tips for taking preworkout supplements

If you’re new to preworkout supplements, you may still have questions about the details. After you’ve determined it’s safe for you to take a preworkout supplement, you should then consider why. It’s best to identify your goals, whether it’s better endurance, more energy, or something else. 

Best time to take it 

Again, this depends on your goals, but also the ingredients. For example, caffeine typically starts to kick in at around 30 minutes. It usually lasts in the body for 4 to 6 hours, but it varies from person to person. If you’re interested in building muscle, the timing of your protein intake may be more important.

How to choose a preworkout supplement

There are so many supplements available, it might feel overwhelming. Once you’re familiar with what you want out of a supplement, you can start shopping by ingredient(s). Know what you’d like to avoid (caffeine, for example, if you work out close to bedtime) and include (creatine, for example, if you want to build muscle mass). You might need some trial and error when it comes to taste and consistency. 

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Written by:

Jody Braverman, CPT, RYT

Jody Braverman has worked in the health and fitness industry –– as a trainer, yoga teacher, nutrition and lifestyle coach, writer, and editor –– for more than two decades. She graduated with a B.A. from the University of Maryland and maintains several accredited certifications.

Edited by:

Lauren Savage, MA

Lauren Savage, MA, is a health editor at GoodRx, where she focuses on movement, exercise, and healthy aging. She aims to provide readers with the information they need to live healthier, more active lifestyles.

Reviewed by:

Mandy Armitage, MD

Mandy Armitage, MD, has combined her interests in clinical medicine with her passion for education and content development for many years. She served as medical director for the health technology companies HealthLoop (now Get Well) and Doximity.

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