Pre-Workout Supplements: 6 Side Effects and How to Avoid Them
You expect to feel something when you take pre-workout supplements. An rush of energy, a tingly sensation, or intense mental focus are often the signs we look for to know it’s working.
But sometimes, those effects come with drawbacks.
In my experience as a certified sports nutritionist, I’ve seen many athletes chase the benefits without understanding the potential consequences. At Weik Fitness, we want you to be informed about how pre-workout supplements work. Some people swear by them, while others have amazing workouts without ever touching the stuff.
This guide will break down the common side effects of pre-workout supplements and give you the strategies to avoid them, so you can get the boost you want without the issues you don’t.
Disclaimer: This article is for informational purposes only and is not meant to treat or diagnose any condition. It is recommended that you speak with your doctor before starting any exercise program, changing your daily nutrition, or adding any supplements to your regimen.
Key Takeaways
- Many side effects are dose-dependent. Starting with a half-scoop of a new preworkout can help you assess your tolerance.
- Hydration is critical. Drinking enough water before and during your workout can prevent headaches, dehydration, and digestive issues.
- Timing matters. Consuming pre-workout supplements with high stimulant content less than 6-8 hours before bed can disrupt your sleep.
- Specific ingredients cause specific reactions. Beta-Alanine causes tingles, and vasodilators like Citrulline can cause headaches in some people.
6 Side Effects of Pre-Workout Supplements
Below are six common side effects of pre-workout supplements you need to be aware of and, more importantly, how to manage them.
1) Insomnia
If you train at night, the caffeine in your preworkout could be the reason you’re staring at the ceiling instead of sleeping. It’s critical to check the supplement label to see just how much caffeine you’re consuming, as this is the most common cause of workout-related insomnia.
Most pre-workout supplements are loaded with caffeine, often containing 200-400mg per serving. For context, a standard 8-ounce cup of coffee has around 95mg, while a single serving of a popular pre-workout like C4 Ultimate has 300mg. The FDA sets the recommended daily limit at 400mg for healthy adults, so one scoop can get you close to that line.
The caffeine gives you a great energy boost by activating epinephrine and norepinephrine. The downside is that its half-life, or how long it lasts in your system, is three to five hours for most people.
If you plan to be in bed by 11 pm, taking a caffeinated preworkout after 6 pm is a gamble. For some people who metabolize caffeine slowly, even a lunchtime dose can interfere with sleep. You can try lowering your serving size to see if a smaller dose exits your system faster.
A better solution for evening workouts is to use a stimulant-free preworkout. Many brands offer versions that skip the caffeine and focus on “pump” ingredients like L-Citrulline to enhance blood flow.
Related Article: Why is Dry Scooping Pre-Workout a Stupid TikTok Trend?
2) Diarrhea
Digestive upset is a common and unpleasant side effect for some preworkout users. This often comes down to specific ingredients that can have a laxative effect, especially if you have a sensitive stomach.
Several ingredients can be the culprit, but it’s important to know why they cause issues. Your body’s reaction can be triggered by:
- High Doses of Certain Minerals: Ingredients like Magnesium Citrate are osmotic laxatives, meaning they draw water into your bowels, which can lead to a quick trip to the bathroom.
- Artificial Sweeteners: Many formulas contain sugar alcohols like sorbitol and xylitol for flavor. These are not fully absorbed by the body and can cause gas, bloating, and diarrhea.
- Too Little Water: This is a very common mistake. Most labels recommend mixing a scoop with about 8 ounces of water, but this isn’t always enough. A highly concentrated drink can form a paste in your gut that your body tries to flush out.
The fix is often simple. Try mixing your pre-workout supplements with 12-16 ounces of water instead of the recommended 8. If you’re trying a new product, start with a half-scoop to see how your system reacts before taking a full dose.
3) Dehydration
Certain ingredients in pre-workout supplements can pull water from your body, increasing your risk of dehydration. This happens when ingredients act as diuretics, causing you to excrete more fluid. Even ingredients with performance benefits, like creatine, increase your body’s demand for water.
Creatine monohydrate works by pulling water into your muscle cells. While this is great for performance and muscle growth, it means there is less water available for other essential bodily functions. Combined with fluid loss from sweating, this can quickly lead to dehydration if you’re not drinking enough.
To combat this, proper hydration is key. The American Council on Exercise (ACE) recommends drinking 17 to 20 ounces of water two hours before exercise and another 8 ounces 20 to 30 minutes before you start. Make sure you continue to sip water throughout your workout.
4) Headaches
A headache after taking your preworkout is often tied to other side effects. Dehydration is a primary cause. Your brain is protected by a layer of fluid, and when you become dehydrated, this fluid decreases, which can cause your brain to slightly bump against your skull, triggering a headache.
Another cause is vasodilation, which is the widening of your blood vessels. Ingredients like Citrulline Malate or Beta-Alanine are included to increase blood flow and give you that “pump” feeling. While effective, this rapid change in blood flow can cause headaches in some individuals.
Formulas with high doses of these vasodilators, sometimes over 6-8 grams per serving, are more likely to be the culprit. If you consistently get headaches, consider switching to a preworkout with a lower dose of pump-focused ingredients or simply reducing your serving size.
5) High Blood Pressure
Stimulants, by their very nature, increase blood pressure. Ingredients like caffeine cause a temporary spike, which is a normal part of their function. However, this can be a serious issue if you already have high blood pressure or are sensitive to stimulants.
Weight training and high-intensity exercise can also temporarily raise your blood pressure. When you combine that with a potent preworkout, the effect is magnified. If your doctor has told you that you have high blood pressure, you should avoid any pre-workout supplements that contain stimulants.
To stay safe, look for these ingredients on the label and choose a product without them if you have any concerns:
- Caffeine: The most common stimulant.
- Synephrine: Derived from bitter orange, this compound can significantly increase heart rate.
- Yohimbine: Another powerful stimulant that can cause anxiety and spikes in blood pressure.
Always consult with your doctor before starting any new supplement regimen, especially if you have a pre-existing health condition. If you want to use a preworkout, opt for a stimulant-free version to be safe.
6) Tingly or Prickly Sensations
That tingly or prickly feeling you get after taking some pre-workout supplements has a name: paresthesia. It’s a harmless side effect of a specific ingredient reacting with your nervous system. While some people enjoy the sensation as a sign the product is “kicking in,” others find it uncomfortable.
The ingredient almost always responsible for this feeling is Beta-Alanine. It’s an amino acid that helps buffer acid in muscles during intense exercise, which improves endurance. The tingling sensation typically occurs at doses of 2 grams or more per serving.
Some brands also include high doses of Niacin (Vitamin B3) to cause a “flushing” effect, where your skin can become red and itchy. They do this because users often associate a physical feeling with product effectiveness.
If you don’t like the tingles, the solution is simple. Check the label for Beta-Alanine or Niacin and choose a product that either doesn’t contain them or has a lower dose. The sensation will always subside on its own, but you can avoid it entirely by choosing the right formula for you.
FAQs About Pre-Workout Supplements
How can I choose a safe pre-workout supplement?
Look for products that have been third-party tested by organizations like NSF Certified for Sport or Informed-Sport. This certification ensures that what’s on the label is actually in the product and that it’s free from banned substances or harmful contaminants.
Do I need to cycle my pre-workout?
Yes, especially if it contains stimulants. Over time, your body builds a tolerance to caffeine, meaning you’ll need to take more to feel the same effect. I recommend my clients take a 1-2 week break from all stimulants every 6-8 weeks to reset their tolerance.
Can I just drink coffee instead of taking a pre-workout?
Coffee is a great source of natural caffeine for energy. However, pre-workout supplements contain other ingredients designed to improve performance in different ways, such as L-Citrulline for blood flow and Beta-Alanine for muscular endurance. If you only want an energy boost, coffee is a fine choice. If you want a more comprehensive performance formula, a preworkout is a better option.
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