5 Serious Side Effects of Pre-Workout

Pre-workout supplements combine various amino acids and stimulants to help increase energy and performance during your workout. However, pre-workout ingredients can also cause unwanted side effects such as nausea, anxiety, and skin tingling.

Pre-workout stimulants like caffeine (caffeine anhydrous or guarana extract), synephrine (bitter orange extract), theacrine, and yohimbe give you energy by increasing brain chemicals that regulate mood and attention.

Stimulants can also increase your stress hormones, which is why a pre-workout high in stimulants can leave you feeling shaky, agitated, and anxious. If you do a pre-workout too close to bedtime, stimulants like caffeine can linger in your bloodstream and make it difficult to fall asleep.

Highly stimulating pre-workouts can also increase heart rate by narrowing blood vessels. This effect can increase your blood pressure and cause your heart rate to increase or increase. You may also feel like your heart is skipping beats (called palpitations).

If you experience chest pain, heart palpitations, or dizziness after doing a pre-workout, talk to your healthcare professional. Heart palpitations are a sign that your heart is working too hard and may be damaged.

Pre-workout may cause tingling or numbness in your arms, hands, feet, or legs. This sensation is called paresthesia, or “tingling.”

Amino acids present before training, called β-alanine, cause this feeling when they interact with nerve receptors in your skin. The itching or tingling sensation may stop as your body gets used to taking pre-workouts or if you start taking lower doses.

Pre-workout with high doses of niacin (vitamin B3) can also cause red, hot, tingling, and itchy skin on the face, neck, and chest. This is called a niacin flush and is caused by niacin widening the small blood vessels near the surface of your skin and increasing blood flow.

Pre-workout ingredients like L-citrulline, arginine alpha-ketoglutarate (AAKG), caffeine, and niacin can all irritate your digestive tract. This can cause side effects like nausea, cramps, or bloating. Creatine added to pre-workout can also draw water to the intestines, causing diarrhea and stomach pain.

You are more likely to experience digestive issues if you do the pre-workout on an empty stomach. High doses of pre-workout can also cause stomach upset.

Stimulants added before training can increase urination (pee), while amino acids like β-alanine can increase sweating. Excessive fluid loss causes dehydration and associated symptoms such as muscle cramps, headaches and fatigue.

Dehydration can also put strain on your heart, leading to heart palpitations.

Pre-workout side effects are usually temporary, but cardiac side effects can be serious. Check ingredient labels to identify ingredients and high doses that may cause side effects. You can also work with a healthcare professional, such as a dietitian, who can help you choose a pre-workout that’s best for you.

Other ways to avoid or reduce pre-workout side effects include:

• Take smaller doses if you’re following a new pre-workout
• Don’t take a pre-workout on an empty stomach
• Avoid taking a pre-workout within six hours of bedtime
• Drink plenty of water to stay hydrated
• Try Caffeine-Free or Non-Stimulant Pre-Workouts
• Choose a pre-workout that lists stimulant doses

When purchasing a pre-workout, you should also look for third-party verification from organizations like NSF Certified for Sport or Informed-Sport. These organizations test supplements for contaminants and banned substances.