Pre-Workout Side Effects (and How to Avoid Them)

A pre-workout is a supplement taken shortly before exercise. People take this type of product primarily to boost energy, increase focus, enhance muscle recovery and increase athletic performance. Certain pre-workouts are also formulated to increase vascularity and enhance muscle pumps.

Sounds good, right?

But as with any type of supplement, pre-workouts CAN cause side effects. In this piece, we go through some of the more common issues, before providing advice on what to look out for. That way, you’ll be less likely to experience them…

Pre-workout side effects:

1. Insomnia

Disturbed sleep appears to be one of the more common pre-workout side effects. And the reason appears to be that many of them contain caffeine as a primary ingredient. This stimulant is said to increase energy and focus, and could even increase motivation[1] and strength[2].

While this popular stimulant is said to be safe when taken in the right amounts, many pre-workouts contain too much. But how much is too much?

According to Mayo Clinic, 400mg of caffeine per day ‘appears to be safe for most healthy adults’[3]. Now when you consider that many pre-workouts contain this amount (or more! – ed) in one serving, it’s not hard to see why taking them could lead to sleeping issues.

Insomnia is a pre-workout side effect

2. Itching and tingling

Another common side effect is itching and tingling sensations on the skin. The medical term for this is paresthesia[4], but it is also widely known as “beta-alanine itch”. This is because the modified amino acid is said to be a primary cause of such issues.

Beta-alanine users have reported feeling these tingling sensations on the face, neck or back of the hands.


While paresthesia appears to be harmless and some people say they like the sensations, while others find them unpleasant and report that they ruin their workouts.

3. Headaches

There are a number of reasons why you may experience headaches after taking a pre-workout. Here are two main reasons…

First, some pre-workout ingredients could cause dehydration. As caffeine is a diuretic, too large a dose could reduce how much water your body is able to retain[5]. Without proper hydration, the body is said to be less likely to perform at its best. That said, smaller amounts of caffeine are thought to help improve athletic performance.

Second, some pre-workouts contain ingredients that increase blood flow. For example, L-citrulline is said to help achieve this by boosting nitric oxide in the blood[6]. This in turn could help reduce muscle soreness, aid recovery and promote more intense muscle pumps.

However, increased blood flow could also lead some users to experience headaches or migraines[7].

Headaches are a pre-workout side effect

4. Water retention

Creatine is thought to be one of the best-researched supplements on the market[8]. It is said to improve performance during short bursts of high-intensity exercise[9] and is widely used by athletes to improve muscle strength and size.

Some people experience bloating – which usually happens during the loading phase. This loading method involves taking 20-25g of creatine per day for up to a week, which is thought to help increase muscle mass and body weight faster. On average, users could increase body mass significantly during this early stage – much of which may come as a result of water retention[10].

Not everyone experiences bloating. Those who do feel discomfort usually get through the worst of their symptoms within a few weeks of the end of the loading phase.

5. Skin rashes

Of course, rashes can be caused by allergic reactions. And it’s important that you check labels for any ingredients you may be sensitive to – which goes for any type of supplement, not just pre-workouts.

Another reason you may experience rashes is due to niacin flush – which can occur if you take a supplement containing a certain form of niacin (also known as vitamin B3)[11].

There are two forms of niacin: nicotinic acid and niacinamide (also known as nicotinamide). B3 is an essential nutrient. But in supplement form, nicotinic acid is thought to cause flushing on the neck, chest and face.

6. Jitters and anxiety

As we state earlier, caffeine plays a key part of many pre-workout products due to its potential to increase energy, focus and athletic performance[12].

However, caffeine (and other stimulants) can cause anxiety and jittery feelings when taken in high amounts[13].

All too often, the issue appears to be that some pre-workouts contain too much caffeine – sometimes more than 400mg in a single serving. As 400mg is the maximum daily amount recommended by experts[14], taking this amount all at once could give the user the shakes.

Why? Because large amounts of caffeine could increase epinephrine (also known as adrenaline), which is said to:

  • Raise the heart rate
  • Increase restlessness
  • Promote sweating
  • Induce jitteriness

7. Digestive issues

There are several ingredients that could cause diarrhea and other forms of digestive upset. These include everything from caffeine, to magnesium, sodium bicarbonate and creatine.

Caffeine is said to promote movement in the colon by 60% more than water[15], while magnesium is also said to have a laxative effect in large amounts[16].

Furthermore, when sodium bicarbonate mixes with stomach acid, it can lead to bloating, gas and diarrhea[17].

Lastly, large amounts of creatine (over 20g per day) have been linked to stomach pain, diarrhea and nausea[18].

Ways to avoid pre-workout side effects

To avoid potential pre-workout side effects, you could avoid this type of product altogether – but then you wouldn’t get any of the benefits either. By simply paying a little more attention to what you put in your body, you could reduce – or even eradicate – at least some of the issues described in this article.

Here’s how:

Look at the label

This might seem obvious, but failure to look at the label appears to be a common issue among consumers.

It’s important to look at both the ingredients AND their serving sizes. This helps ensure you can be sure WHAT and HOW MUCH the product contains. This could help you avoid taking ingredients that could set off allergic reactions; it could also help you avoid taking too much of a certain ingredient.

But here’s the problem…

By law, supplement companies are not obligated to disclose either the ingredients or dosages in a product. Instead, many brands hide their formulas in proprietary blends with names like MAXPOWER 2000® (made up name).

With this in mind, we advise ignoring pre-workouts with these hidden formulas in favor of those which have transparent ingredients and servings.

Drink more water

Experts say good hydration is vital for optimal athletic performance[19]. This is said to be because water helps keep the body cool and could ensure you get the most out of your gym sessions.

Woman drinking water

Could reduce headaches

Staying hydrated could help reduce the risk of headaches[20] which may be caused by diuretics like caffeine. 

Proper hydration is also thought to help counteract diarrhea[21].

Get ‘smart’ with L-theanine

Earlier in this piece, we stated that larger-than-normal amounts of caffeine and other stimulants could cause anxiety and jittery feelings.

But when mixed with L-theanine, caffeine is said to enhance benefits while also reducing anxiety[22]. L-theanine is also thought to improve sleep quality[23].

For these reasons, the blend of caffeine and L-theanine is known as ‘smart caffeine’. If you’re sensitive to caffeine and want to avoid the jitters, it may be wise to look for a pre-workout that also features L-theanine.

Find the right kind of niacin

As established earlier in this piece, supplementing with niacin could cause niacin flush – which often takes the form of red blotching on the skin.   

Research suggests that of the forms of niacin (vitamin B3), it is nicotinic acid (and not niacinamide) that has been shown to cause niacin flush.

For this reason, it may be a good idea to choose a pre-workout that does not contain nicotinic acid (niacinamide is thought to be fine).

Take the recommended amounts

Before you buy a pre-workout, it’s important to check that amounts of each ingredient don’t go beyond the recommended daily amounts (RDA). So, if a single serving of a product features a whole day’s worth of caffeine (400mg) in one go, it may be wise to avoid it – or at least halve your dose.   

This principle also applies to creatine – and to its potential side effects. This compound is perhaps the most well-researched supplements there is.

Very often, the problem of bloating seems to be caused by ‘loading’ 20-25g of creatine monohydrate per day for 5-7 days. To avoid water retention, you may wish to consider cutting your intake to a maintenance dose of 5g per day for a month. 

The Final Word

If you suffer from pre-workout side effects – or you’re worried you might – it could be easy enough to avoid them.

Pre-workouts offer a number of benefits – from increased energy, to enhanced focus and motivation and more intense muscle pumps. For this reason, we don’t (necessarily) advise stopping – or avoiding – them altogether.

Instead, we recommend taking note of the advice in this article. Use this post to learn about what ingredients are liable to cause which pre-workout side effects – and take a note of whether it’s wise to lower the amount you take or avoid the ingredient.

Get the good without the bad

For example, let’s say you want to avoid bloating – it’s perhaps better to lower your dose of creatine than to stop taking it altogether. This is because a great deal of research highlights its potential benefits on exercise performance.

The same goes for caffeine. While thought to cause anxiety in high amounts, the stimulant is said to boost energy, attention and mood. But if you find that a product contains too much caffeine, taking a smaller amount may do the trick. It may also be wise to find a pre-workout that contains both caffeine and L-theanine – a smart blend that could help reduce anxiety.

On the other hand, if you find the tingling sensations caused by beta-alanine to be off-putting, it could be a good idea to avoid the ingredient altogether.
























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