:max_bytes(150000):strip_icc()/VWH-GettyImages-1776133642-5a2b0fc0737141d88b20687f4aa4973a.jpg?w=780&resize=780,470&ssl=1 "8 Serious Side Effects of Pre-Workout Supplements")
Key takeaways
- Pre-workout supplements may give you energy but may cause nervousness or nausea, with side effects depending on the ingredients and dosage.
- Choose stimulant-free options or smaller doses to reduce risks.
- Talk to a healthcare professional before using pre-workout supplements if you have heart or blood pressure problems.
Pre-workout supplements can improve focus, boost energy and delay fatigue. However, they can also cause unwanted side effects ranging from mild nervousness to serious reactions.
1. Nervousness
Many people feel shaky, agitated, or nervous after taking pre-workout supplements. This effect can make it difficult to concentrate or perform controlled movements without contractions.
The main culprits are caffeine anhydrous, synephrine (bitter orange extract), and theacrine, which stimulate the central nervous system and increase adrenaline. This delays fatigue but can also cause nervousness.
2. Anxiety
Some pre-workout users report feeling anxious, irritable, or “too excited” after ingesting a pre-workout. People prone to anxiety may notice racing thoughts or tensions, even at lower doses.
This reaction is usually caused by yohimbine (a plant alkaloid that stimulates the nervous system), caffeine or synephrine, which increase norepinephrine levels and have anxiogenic (anxiety-inducing) properties.
What is pre-workout?
Pre-workout products typically combine stimulants, amino acids and other compounds to improve exercise performance. Since formulas vary widely, it’s important to know what’s in your pre-workout before taking it.
The FDA does not regulate pre-workouts in the same way as prescription drugs. If possible, consult a dietitian or sports nutritionist before taking a supplement that contains ingredients that are not approved by the FDA.
3. Nausea and stomach upset
Nausea, bloating, or stomach cramps are common, especially when pre-workouts are taken on an empty stomach or in high doses.
Ingredients that may irritate the gastrointestinal tract include L-citrulline, arginine alpha-ketoglutarate (AAKG), and niacin (vitamin B3). High doses of niacin can also cause redness and warmth of the skin called “niacin flushes.”
4. Tingling/itching
Pre-workout users may experience a temporary “tingling” sensation, paresthesias, characterized by tingling or itching.
The amino acid β-alanine causes this feeling. Although it may be alarming, paresthesias caused by β-alanine are not dangerous and occur when β-alanine interacts with nerve receptors in the skin. The feeling usually subsides as your body adapts to the supplement or reduces the dose.
5. Insomnia and sleep disorders
Taking a pre-workout too close to bedtime can make it difficult to fall asleep or stay asleep. Even if you don’t feel ready, the psychostimulants in some pre-workouts can disrupt sleep quality, especially if taken after 4 p.m.
Caffeine can cause insomnia, especially in forms like caffeine anhydrous or guarana extract. These ingredients can persist in the blood for several hours. Avoid “stimulating” pre-workouts within six hours of bedtime.
6. High blood pressure
Pre-workout stimulants can increase blood pressure, which may pose additional risks for people with hypertension. The main contributors are caffeine, synephrine and yohimbine, which can strain the heart.
7. Heart palpitations
Feeling your heart skip beats or pound in your chest after taking a pre-workout supplement can be disconcerting. Palpitations are a warning sign that your heart is working too hard.
Heart-related side effects usually come from excessive amounts of caffeine, synephrine, or theobromine. Proprietary “high stim” pre-workout blends do not always list stimulant amounts. To stay safe, choose products that clearly state the amounts of stimulants per serving.
8. Dehydration
Some pre-workout formulas make you sweat and urinate more, which can lead to mild dehydration. This loss of fluid can cause fatigue and muscle cramps. To avoid cramping, stay hydrated and replace electrolytes such as sodium and potassium during exercise.
Stimulants like caffeine, theacrine, and yohimbine have diuretic (promoting urination) properties, while ingredients like β-alanine can intensify sweating. All of these compounds can contribute to fluid loss and subsequent dehydration.
Is dry pre-workout dangerous?
Yes. Taking pre-workout powder without water (i.e. “dry taking”) can cause choking, irregular heartbeat, or caffeine overdose. Always follow mixing instructions on the label.
When to See a Health Care Provider
Although most side effects are mild and temporary, some may signal a more serious reaction. Consult a doctor if you experience chest pain, heart palpitations, dizziness, or a spike in blood pressure after using pre-workout supplements. Some pre-workout ingredients may also interact with prescription medications such as antidepressants or blood pressure medications.
How to reduce side effects
To reduce the side effects of pre-workout supplements, be sure to:
- Read ingredient labels carefully.
- Choose caffeine-free or “non-stimulating” formulas.
- Start with a lower dose to test tolerance.
- Avoid using it late in the day to prevent insomnia.
- Drink plenty of water before, during and after training.
When purchasing supplements, look for third-party verification, such as NSF Certified for Sport or Informed-Sport, which tests for contaminants and banned substances.
If you’re not sure which supplements are right for you, a dietitian or sports nutritionist can help you choose pre-exercise nutrition that avoids unwanted side effects.
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