Pre-workout supplements are linked to adverse effects such as digestive disturbances, fluid retention, and headaches. Tweaking your dose or steering clear of supplements containing certain compounds can help reduce these issues.
To elevate energy and performance during workouts, many individuals turn to pre-workout blends.
These products typically come as flavored mixes of multiple components, each intended to enhance some aspect of performance.
Still, some users report unwanted effects after using them.
Below are 5 possible side effects of pre-workout supplements — along with suggestions for avoiding them.
1. Can make you feel jittery
Caffeine is a key component in numerous pre-workout products.
This stimulant has been demonstrated to boost muscle strength and output during exercise while lessening fatigue. In principle, caffeine helps you squeeze more out of a training session.
However, caffeine can produce several potential side effects, particularly if consumed in excess. These may include:
- jitteriness
- insomnia
- nausea
- elevated heart rate
- headaches
- anxiety
- restlessness
Moreover, many pre-workout products contain substantial amounts of caffeine per serving — sometimes up to 500 milligrams (mg). Serving sizes usually range from 0.35 to 1 ounce (oz), or 10 to 30 grams (g).
For comparison, 1 cup (240 milliliters [mL]) of coffee contains only .
Ways to reduce side effects
Caffeine tolerance varies widely between individuals.
The safest approach to limit side effects is to begin with a small amount of a caffeinated pre-workout, slowly raising the dose to determine what you can tolerate.
Some evidence indicates it’s best to avoid coffee within 9 hours of bedtime or pre-workout supplements within 13 hours of sleep to reduce insomnia risk.
Also consider opting for caffeine-free pre-workout options.
2. Can increase water retention
Creatine is another widespread ingredient in pre-workout mixes. It has been shown to support:
- enhanced high-intensity exercise capacity
- greater lean body mass
- increased muscle strength, power, and size
- shorter recovery intervals
Though often included in pre-workout blends, creatine is also commonly taken by itself.
The most frequently reported side effect of creatine is weight gain, which is likely due to increased water retention.
There are also anecdotal accounts of other issues, such as digestive discomfort, dehydration, and muscle cramping. Nevertheless, the International Society of Sports Nutrition notes these have not been confirmed in clinical trials.
Ways to reduce side effects
Despite potential complaints, creatine is considered very safe.
You can lower the chance of adverse effects by following recommended dosing.
Commonly, creatine is started with a loading protocol of 5 g four times daily for 5–7 days, followed by a maintenance dose of 3–5 g per day. In certain situations, larger doses may be advised.
This approach yields rapid results but may increase the likelihood of anecdotal issues such as bloating and digestive upset.
Alternatively, taking a single 3 g daily dose for 28 days gradually raises muscle creatine levels, though benefits for performance will emerge more slowly.
Keep in mind that avoiding modest weight gain while using creatine can be difficult, mainly because muscles retain more water.
3. Can cause mild reactions
Two other common additives in pre-workout products are beta-alanine and niacin (vitamin B3).
Beta-alanine
Beta-alanine is an amino acid that helps reduce muscle acidity during exercise, which may let you sustain effort for a bit longer.
Doses in the range of 1.5 to 6.4 g per day may improve performance and decrease fatigue during high-intensity activity.
However, this compound can produce paresthesia — a tingling feeling in the hands and feet. Although harmless from a neurological standpoint, some people find it unpleasant.
Niacin
Niacin is often included in pre-workout formulas for its skin-flushing properties. In high doses of or more, it can cause blood to rush to the skin’s surface, producing red patches known as niacin flush.
Niacin is also important for normal physiology, but supplementing likely offers little extra benefit if you already eat a balanced diet.
Additionally, one even reported that taking 1,000 mg of niacin before an aerobic session actually worsened exercise performance.
Ways to reduce side effects
The best way to lessen beta-alanine’s tingling is to split a daily 4 g dose into smaller portions of roughly 1.6 g each. You can also choose sustained-release versions that blunt this reaction.
To manage niacin flush, keep niacin doses under 500 mg, avoid hot showers right after taking niacin, or consider taking aspirin or ibuprofen beforehand to reduce flushing.
Alternatively, select pre-workout products that list no niacin by checking the ingredient panel.
4. Can cause digestive upset
Several components in pre-workout mixes may lead to stomach issues, including sodium bicarbonate, magnesium, and caffeine.
Sodium bicarbonate can provoke nausea, headaches, and increased urination when consumed at doses above 0.3 g per kilogram of body weight, though most pre-workout products do not reach that level.
Magnesium — especially in magnesium citrate form — can have laxative effects, so taking may cause diarrhea. If you want specific guidance on magnesium, see more on magnesium benefits.
Ways to reduce side effects
Mixing your pre-workout supplement with 8 to 12 oz (240 to 350 mL) of water can help lessen digestive side effects.
Because pinpointing the exact ingredient responsible for stomach upset can be difficult, you may need to try different formulations until you find one that agrees with you.
5. Can cause headaches
Citrulline, found in some pre-workout products, increases blood flow to muscles during exercise, which can support muscle growth.
This amino acid elevates nitric oxide levels in the bloodstream.
The usual recommendation for citrulline malate — a common form — is 6 to 8 g. Many supplements deliver smaller quantities and may not achieve the intended effect.
Be aware that increased blood flow affects the brain as well as muscles. In theory, this could contribute to headaches or migraines due to shifts in pressure within the brain’s tiny blood vessels.
Ways to reduce side effects
The most direct way to reduce citrulline-related headaches is to lower your dose.
If headaches persist, choose a pre-workout that does not contain citrulline.
Should you use pre-workout supplements?
Supplements are not required to reap the benefits of exercise.
However, if you’ve been training consistently for at least six months, pre-workout products might help improve your workout capacity.
If you decide to try one, look for a seal from an independent testing organization that verifies quality. Examples include ConsumerLab.com, U.S. Pharmacopeia (USP), and NSF International.
Also, always read ingredient lists carefully for items you might react to. It’s wise to avoid proprietary blends, which obscure the exact amounts of each component.
Frequently asked questions
Is pre-workout harmful for your heart?
It depends on the product and its ingredients. For example, pre-workouts containing synephrine have been associated with chest pain, palpitations, arrhythmias, and even cardiac events.
Carefully follow label directions and consult a physician before using these supplements.
Is it bad to take pre-workout at every session?
This varies with the activity, the specific pre-workout, and training frequency. Using pre-workout too often can lead to tolerance, making standard doses less effective.
Consider using pre-workout up to three times per week before resistance or high-intensity sessions.
Is pre-workout as bad as energy drinks?
It depends on the ingredients. Generally, energy drinks contain more caffeine and sugar than pre-workouts, so consuming them before exercise may cause an energy crash. For comparisons to other supplements that can cause problems when misused, you can read about detox tea side effects or fish oil side effects.
The bottom line
Pre-workout formulas are widely used for their effects on energy and exercise performance.
Yet, they can cause adverse effects including headaches, skin flushing, tingling sensations, and gastrointestinal upset.
Many of these side effects can be minimized by lowering your dose or avoiding products that contain specific problematic ingredients.
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