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

The best pre-workouts are safe to use and won’t cause any side effects – but so many products (even pricey ones) are bound to make you jittery, itchy, scratchy – or worse.

But how can you make sure you don’t experience any of that unwanted bulls***?

Well bro, that’s what we’re here for! For this piece, we’ll list a s*** ton of pre-workout side effects and give you the lowdown on how to avoid each one.

What is pre-workout?

As you’ve clicked on an article called “Pre-Workout Side Effects”, we’re guessing you already know the answer to this question.

Just in case you don’t – a pre-workout is a supplement (usually a drink) you take before your workout for more energy, focus, and endurance in the gym. The best pre-workouts help you lift more and get faster results.

But the worst pre-workouts cause these side effects…

1. Itching


Hundreds of bros we talk to tell us their pre-workout causes itching or ‘prickling’ sensations across their back, face or hands. Some say it feels like a s***load of bugs crawling over their skin.

In another article, we say it feels like “your face is tingling so much that you just want to scratch it off.” And who the f*** wants that? Not us, bro.

Here’s the thing: We always know the culprit. It’s a little b**** of an ingredient called beta-alanine (or β-Alanine).

To be fair, this amino acid can enhance physical performance [1]. But research also proves clear links between beta-alanine and itching (which the whitecoats call ‘paresthesia’) [2]. Paresthesia might be harmless, but hundreds of bros report it wrecks their workouts.

How to avoid itching

Bro – start by throwing that beta-alanine in the f****** trash!

Then consider taking creatine. As one of the best-researched ingredients in the world, creatine also improves strength, power and lean mass [3] – just without the fire ants crawling over your goddamn skin!

Sure, the two work differently, bro. But if you want to perform better in the gym without the itching, we recommend swapping your beta-alanine for creatine.

2. Insomnia


A ton of our readers report problems with pre-workout insomnia – we’ve all been there, bro. And as our brother Les says in a recent article, lack of sleep “leaves you wired, exhausted and can steal your gains too.”

The problem with pre-workouts is most of them are packed full of all kindsa s*** that leave you wired and wide awake for days at a time.

Want gains? Get more sleep!

If you want to make the most gains (ain’t that why you’re here, bro?), getting enough sleep is a big deal. Try to get at least 7-9 hours of sleep every night [4].

By far the biggest reason for pre-workout insomnia is the s***load of caffeine in most of these supplements. Don’t get us wrong – caffeine is an awesome ingredient at the right dose.

Research shows caffeine improves focus [5], endurance and power output [6]. But with some pre-workouts jacked with as much as 700mg of the stim in one hit (wtf, bro!), it’s no shock they make you crash and burn like the low-level bad guys at the start of an Arnie movie.

How to get better sleep

A study published in the Journal of the International Society of Sports Nutrition shows pre-workouts with an average dose of 150-200mg of caffeine improves gym performance [7].

A dose this size is enough to get the gym juices flowing WITHOUT jacking you up for days.

But what if I’m sensitive to caffeine, bro?

Look for a pre-workout that twins caffeine with L-theanine.

The amino is a calming agent that enhances all the focus, energy and endurance caffeine gives you, with none of the excess energy or sleep issues [8] – f****** sweet!

3. Hives and rashes


Pre-workout hives are a little less common than say, beta-alanine itch.

But check out the forums and you’ll read enough reports of bros taking a pre-workout and wakin’ up one morning to find red blotches their arms, back, neck, chest – and even their f****** feet!

That’s pre-workout hives, bro! And the culprit? Usually (but not always) niacin (vitamin B3). While niacin is a vital nutrient, too much of it can cause rashes – otherwise known as ‘niacin flush’ [9].

How to avoid pre-workout rashes

Avoid taking niacin in a supplement. The RDA for B3 is just 16mg [10] – and it’s easy to get that from a normal, healthy diet.

Where, bro? Chicken, white fish, tuna, soy, peanuts, pumpkin seeds [11]… all these foods are full of B3 – and they ensure you don’t need to get any more in a pre-workout.

If you take a pre-workout that doesn’t contain niacin and it’s still making you break out in a rash – stop taking it straight away and swap it for something different.

4. Anxiety


As Broseph Brah says in a piece from 2017, taking the wrong pre-workouts can lead to “anxiety, jitters and energy crashes.”

And once you take a pre-workout that causes anxiety, you’ll be stuck with the shakes until that nasty s*** wears off! There are thousands of crappy ingredients out there, but here are the worst offenders…

  • Bitter orange – contains chemicals that impact your nervous system. Among these is synephrine – a harsh stimulant shown to cause anxiety, especially when paired with caffeine [12]. This evil pairing will make your heart beat like a f****** jackhammer – not recommended. It’s also banned for competition  – which is no good if you wanna get in the ring, bro.
  • Yohimbe bark extract – while still legal in the US, yohimbe is banned in Canada and Australia [13]. Research shows yohimbe can induce acute anxiety [14] – especially in bros already prone to panic attacks.
  • TOO MUCH caffeine – as we say earlier in the piece, caffeine is an awesome stimulant – you’ll find it in some of our favorite pre-workouts. But in super-high doses (usually around 400mg or more), it’s sure to give even the most hardcore bros the f****** shakes!

How to avoid pre-workout anxiety

First, if your pre-workout’s making you anxious, toss it!

But before you do that, check the ingredients. If you see bitter orange, yohimbe or a s***ton of caffeine, then there’s your answer.

Look for a pre-workout without yohimbe or bitter orange – and find one that contains caffeine in doses of 200mg or less – and we’re willing to bet you lose the jitters.

5. Body odor


An increasing number of bros are reporting their pre-workout makes their sweat and breath smell like rotting fish – jeez, man!

What’s the point makin’ all kindsa gains if your lady don’t wanna go near you ‘cuz you smell like an old man’s a**? Answer: Ain’t no f****** point, brah!

The reason you’ stink could be down to one ingredient…

Betaine. This ingredient can cause trimethlaminuria – or fish odor syndrome [15].

How to stop pre-workout body odor

Start by avoiding pre-workouts that contain betaine. Research shows it doesn’t improve running capacity [16] or endurance [17] anyway, so it’s a pretty useless pre-workout ingredient.

6. Headaches


Dehydration is the primary cause of pre-workout headaches. And this is especially true of pre-workouts that contain creatine. Sure, it’s one of the best-tested workout supplements on Earth [18] – and we recommend it.

But creatine also pulls water from other areas of your body to help support your muscles [19], which can cause headaches.

How to prevent pre-workout headaches

It might seem like we’re giving you mixed messages here – but the answer to dehydration is not to stop taking creatine. Instead, make sure you drink plenty of water. But how much, bro?

You should already be drinking three liters of water per day. But when you start taking creatine, look to add half a liter for every 5g of creatine you put in your body.

7. Diarrhea


Pre-workout-induced turkey trots are more common than you might think (who talks about what they do in the john, bro?).

That’s ‘cuz a buttload of pre-workout ingredients cause laxative effects. These include yohimbe [20], arginine [21], and sodium bicarbonate [22].

But remember when we warned you about getting your caffeine dose right? Well bro, one of the side effects of taking too much is the f****** runs!

How to stem the flow of pre-workout diarrhea

The ingredients listed above affect different bros in different ways, so it’s impossible to say for sure what – if anything – is gonna make your body react in this way.

Once again, if your pre-workout is bustin’ your a**hole loose, stop taking the supplement. But what do you use instead? Just look for an alternative without too much of any ingredient – that way, you’re more likely to dam the flow.

8. High (or low) blood pressure


With so many pre-workout drinks designed to get you amped, it’s no shocker that some of them can cause high blood pressure.

If you find yourself getting severe headaches, vision issues, or an irregular heartbeat – get yourself to the doc, bro!

But what’s causing it?

There’s too many possible culprits to list here, man!

But as we lay down earlier in this piece, we got no time for bitter orange or yohimbe – the latest research links bitter orange to ultra-high blood pressure [23] and yohimbe to severe low blood pressure [24] – f*** that s***!

And we risk soundin’ off like a broke record here – TOO MUCH caffeine can also cause your blood pressure to skyrocket [25].

How to keep your blood pressure in check

Remember too much of any stimulant is bad – stick to the recommended dose.

But be particularly wary of the potentially harmful stims like bitter orange.

Also look for a pre-workout that contains L-citrulline, or (even better) L-citrulline DL-malate. This vasodilator widens your blood vessels to improve blood flow and keep blood pressure at normal levels [26].

9. Stomach pain


Stomach cramps and pain are normal pre-workout side effects – but it don’t have to be that way, bro.

Talking to the guys who suffer pre-workout cramps, it quickly becomes clear they do stupid s***. Some bros hit the treadmill for hours with nothing but pre-workout in their bellies. And others take  an a**load of stimulants without proper hydration – that’s some stoopid s***!

How to avoid stomach pain

Don’t work out on an empty stomach UNLESS you’re gonna eat straight after. And don’t do fasted cardio for more than 20 minutes in the morning.

Drink plenty of water and don’t overdose on the stims.


Unless you have allergies, you can avoid the pre-workout side effects on this list. Just check the label, research the ingredients in your pre-workout and make sure you know what you’re pourin’ down your neck.

Need help, bro?

To see our list of favorite products, check out our Best Pre-Workout awards.


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  15. Shelley, E. (1984). The Fish Odor Syndrome. JAMA, 251(2), p.253.
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