5 Side Effects of Pre-Workout Supplements

1. Serving Size

When pre-workout labels say serving size 'x' grams, it’s generally wise to follow the directions on the label. The serving size noted represents how much is safe and effective. When you take more or less than the recommended amount, what you’re getting is likely not what you could be.

Some people may follow the logic that taking more means better results, but that’s rarely the case.

When blends contain caffeine or other stimulants, nitric oxide boosters, and other ingredients designed to enhance focus, boost energy, and increase muscle pump, more can actually be detrimental to your workout.

So, opting for more doesn’t necessarily equate to better gains. The result is likely going to be some nasty side effects.

2. Proprietary Blends

Proprietary blends are what manufacturers use to keep their “trade secrets.” They’ve got a formula that’s better than all the rest, and they want to keep it protected.

And while these blends aren’t necessarily the worst of the worst, not knowing how much you’re taking can cause some issues, especially with things like creatine, beta-alanine, branched-chain amino acids, caffeine, and the like.

Those ingredients are all super important to performance, but they won’t offer the same extent of benefits in doses outside the research-backed amounts. You could think you’re taking 100 mg of caffeine, when really it’s 500 mg, which means you’re going to feel the side effects of high-dose caffeine.

If you’re trying to avoid any nasty effects from your pre-workout, stay clear of any proprietary blend.

3. Excessive Stimulants

This one can be both a benefit and a drawback, depending on how well your body tolerates stimulants. For most people, high-dose caffeine isn’t the best thing to have in a pre-workout because it can actually do the opposite effect that you want.

In moderate doses, caffeine is known to enhance performance for high-intensity, prolonged activity, but studies show that it does not result in further enhancement in performance when consumed in higher doses (≥ 9 mg/kg) ¹. It may actually cause problems.

For people that metabolize caffeine well, a few hundred milligrams might not result in much aside from better focus and more energy, but for people that metabolize it slower or are more sensitive, it can cause things like rapid heart rate, high blood pressure, dizziness, anxiety, and sleep disturbances.

1. Itchiness and Tingles (“Prickly”)

If you’ve ever knocked back a scoop or two of pre-workout and felt tingly or itchy 20 minutes later, there’s one ingredient you can point the finger at: beta-alanine.

This feeling that happens is what we call paraesthesia, and it’s associated with taking large amounts of the amino acid beta-alanine.

When it comes to muscle building, there’s no denying that beta-alanine is super useful. It’s a major component required to boost intramuscular carnosine levels, one of the most effective buffers to prevent muscle cells from becoming too acidic ². When muscle acidity increases, they are unable to contract, and it causes muscle fatigue.

So, the thought process of supplementing with more beta-alanine to boost carnosine levels may be warranted, but the effect you get from excessive doses is less than ideal, and because beta-alanine is widely distributed not only in the muscles but also in the skin and nervous system, that’s where you feel it most.

The reason is because β-alanine binds to and activates MrgprD receptors in neurons that innervate the skin ².

It’s suggested that these neurons may become hyperexcited, and while the mechanism behind how this happens isn’t completely understood, studies show that the skin sensations caused by beta-alanine are mediated by this MrgprD gene expressed in cutaneous sensory neurons, which causes the skin-specific sensation of itchiness and tingles.

Keep in mind that paresthesia isn’t dangerous and usually subsides about 60-90 minutes after ingestion, but it can be a bit problematic during workouts.

Studies show that large amounts of beta-alanine are not effective for increasing performance outcomes, likely because of strong paraesthesia, rapid changes in pH, higher excretion rates, and the inability to load muscles effectively ³. A sustained-release formula is the best way to avoid this.

2. Jitters

High-dose caffeine is one of the most common side effects with pre-workouts. When their sole purpose is to keep you alert, boost energy, and power you through even the most intense workouts, manufacturers opt for go big or go home.

So, they load their products with upwards of 300 or 400 mg of caffeine per ensuring that you’re getting precisely what you bargained for… better energy and enhanced alertness. But at what cost?

The jitters—that antsy, nervous feeling you get where you just can’t stand still. It’s the result of high levels of circulating catecholamines that cause an increase in heart rate, blood pressure, sweating, nervousness, and shakiness—the typical results of over-caffeination ⁴.

It’s also because caffeine inhibits the effects of the regulatory molecule adenosine, which circulates through the body and keeps organs like your heart and lungs in check, but also plays an important role in the nervous system. When caffeine blocks these receptors, things can get a little whacky.

3. Insomnia

The roots of insomnia can be linked to several factors, but where pre-workouts are concerned, it’s generally the result of excessive stimulants.

Caffeine is hands down one of the most popular ergogenic aids used in pre-workout formulas to increase energy and focus, enhance mental alertness, boost memory, and maximize exercise performance and fat burn.

And a lot of supplement companies are under the impression that more caffeine means better performance.

But in high doses, caffeine can lead to a lot of adverse side effects like high blood pressure, rapid heart rate, irritability, nervousness, anxiety, nausea, and insomnia.

Studies show that chronic high dose caffeine intake can result in more inferior sleep quality, increased sleep latency, decreased slow-wave sleep, increased sleep fragmentation, and a decreased sleep duration ⁵.

But the other reason we can’t sleep after caffeine consumption is because it releases a cascade of stress hormones that cause arousal and prevent fatigue ⁶.

So, taken too late in the day, your pre-workout supplement will likely be a massive impediment to sleep, which, we all know, is critical to recovery and next-day function.

4. Water Retention And Bloating

One of the most popular pre-workout ingredients, and most popular fitness supplements in general, is creatine.

It undoubtedly offers some pretty powerful effects on boosting muscle growth, but one of the most common side effects is water retention. If you’ve ever had someone tell you that creatine makes you puffy, that’s what they’re talking about.

Water retention is most frequently associated with creatine loading—consumption of 20-25g of creatine daily for 5-7 days to max out muscle creatine stores.

The theory behind this is that increased muscle creatine concentration enhances work capacity of the phosphagen energy system, thereby providing greater resistance to fatigue and improving overall performance ⁷.

Other side effects like gastric distress, muscle spasms, strains, and cramping are associated with high doses of creatine, but water retention and weight gain are the most common due changes in intracellular osmotic pressure, which causes movement of water into the cell, water retention, and weight gain ⁷.

5. Headaches

Whether headaches happen from pre-workouts will largely depend on the specific pre-workout supplement, but a staple in a pre-workout is vasodilating compounds, generally nitric oxide boosters, which have been implicated in the pathophysiology of headaches and migraines ⁸.

NO boosters aim to dilate blood vessels to increase blood flow to working tissues. The more blood that can get to muscles, the better the workout. NO compounds are also responsible for that notorious ‘pump’ that bodybuilders and lifters strive for.

But the one thing that people don’t tell you about vasodilating compounds is that when it opens up blood vessels to increase circulation to the muscles, you’re also increasing circulation to the brain. And blood vessel dilation in the brain can cause headaches.

The compounds used to maximize vasodilation in pre-workout supplements are usually arginine, citrulline, and beta-alanine, all of which increase endothelium-dependent nitric oxide (NO) production ⁹, and by increasing NO during exercise, you experience greater muscle hyperemia (blood flow) and decreased muscular fatigue during training.