Pre-workout supplements combine various amino acids and stimulants to help boost energy and performance during your workout. However, pre-workout ingredients can also cause unwanted side effects like 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 elevate your stress hormones, which is why a high stimulant pre-workout can make you feel shaky, restless, and anxious. If you take pre-workout too close to bedtime, stimulants like caffeine can linger in your bloodstream and make it difficult to fall asleep.
High stimulant pre-workouts can also make your heart beat faster by narrowing blood vessels. This effect can raise your blood pressure and cause a racing or pounding heart rate. You may also feel like your heart is skipping beats (known as palpitations).
If you have chest pain, heart palpitations, or dizziness after taking pre-workout, talk with your healthcare provider. Heart palpitations are a sign that your heart is overworking and could become damaged.
Pre-workout can make your arms, hands, feet, or legs feel tingly or numb. This feeling is called paresthesia, or “pins and needles.”
Amino acids in pre-workout called β-alanine cause this sensation when they interact with nerve receptors on your skin. The itchy or tingly feeling may stop as your body gets used to taking pre-workout or if you start taking lower doses.
Pre-workout with high doses of niacin (vitamin B3) can also cause red, warm, tingly, and itchy skin on the face, neck, and chest. This is called niacin flush and is caused by niacin widening 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’re more likely to experience digestive issues if you take pre-workout on an empty stomach. High doses of pre-workout can also cause an upset stomach.
Stimulants added to pre-workout can increase urination (peeing), while amino acids like β-alanine can increase sweating. Losing too much fluid causes dehydration and related symptoms such as muscle cramps, headaches, and fatigue.
Dehydration can also strain your heart even more, leading to heart palpitations.
Pre-workout side effects are usually temporary, but heart-related 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 provider, such as a registered dietitian, who can help you choose a pre-workout that works better for you.
Other ways to help avoid or reduce pre-workout side effects include:
- Take smaller doses if you’re taking a new pre-workout
- Don’t take pre-workout on an empty stomach
- Avoid taking 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 the stimulant dosage amounts
When shopping for 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.
