Fitness & Muscle

Pre-Workout Supplements: What Works, When to Take It, and What to Skip

Compare the evidence, doses, timing, limitations, and safety considerations for caffeine, creatine, beta-alanine, citrulline, and other common pre-workout ingredients.

Last updated: September 1, 2026

Medically Reviewed By: Rhonda Collins, FNP-C | September 1, 2026 | 10 min read

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The most useful pre-workout ingredients depend on the job. Caffeine can help some people perform better in a single session. Citrulline may offer a small acute benefit for muscular endurance. Creatine and beta-alanine are different: they work through repeated daily use, not because you take them minutes before training. No supplement replaces sleep, food, hydration, or a training plan, and more ingredients do not make a formula more effective.

This guide compares the evidence, study doses, timing, likely benefit, limitations, and safety considerations. The ranges below describe research protocols, not a personalized regimen. Individual responses vary. Anyone who is pregnant, breastfeeding, under 18, managing a health condition, or taking medication should discuss supplements with a qualified clinician or pharmacist.

Quick comparison: acute versus daily ingredients

These evidence categories are summaries, not guarantees. Study populations are often small, young, healthy, and already active. Results may not transfer to every sport, training status, sex, age, or health condition.

Caffeine: an acute option with the strongest overall evidence

Bottom line: Caffeine can improve several exercise outcomes in some people, but the effect and side effects vary. It is the ingredient most likely to interfere with sleep or make a stimulant-heavy formula a poor tradeoff.

• Evidence strength: Strong overall. An International Society of Sports Nutrition position stand found small to moderate benefits across aerobic endurance, muscular endurance, movement velocity, strength, sprinting, jumping, and sport-specific tasks, although not every study found a benefit.
• Dose studied: Performance studies most consistently support 3 to 6 mg/kg. The same review notes that the minimum effective dose is unclear and may be about 2 mg/kg, while 9 mg/kg produces more side effects without being necessary for benefit.
• Timing studied: About 60 minutes before exercise is common for caffeine capsules. Timing varies with the caffeine source and when an effect is needed.
• Likely benefit: Aerobic endurance has the most consistent evidence. Effects on strength, sprinting, and power are smaller and more variable.
• Limitations: Habitual intake, genetics, dose, time of day, and exercise type can change the response.
• Safety: Caffeine can cause anxiety, jitters, digestive symptoms, a faster heartbeat, higher blood pressure, and sleep disruption. The FDA cites 400 mg per day as an amount not generally associated with negative effects for most adults, but it is not a target or a safe limit for everyone. Add caffeine from coffee, energy drinks, medication, and supplements together. Avoid pure or highly concentrated caffeine powders and liquids because small measuring errors can be dangerous.

Sources: ISSN position stand on caffeine and exercise, FDA guidance on caffeine intake, and FDA warning on concentrated caffeine.

If a performance benefit costs you sleep that night, it may be a net loss for recovery. A systematic review and meta-analysis found that caffeine reduced total sleep time and sleep efficiency, with the effect depending on dose and timing. Rather than relying on a universal cutoff, account for bedtime, total dose, and personal sensitivity. Read more about caffeine’s benefits, tradeoffs, and responsible use.

Source: systematic review and meta-analysis of caffeine and sleep.

Creatine monohydrate: strong evidence, but not an acute pre-workout

Bottom line: Creatine supports repeated high-intensity exercise and training adaptations after muscle stores build up. Putting it in a pre-workout can be convenient, but immediate pre-exercise timing is not what makes it work.

• Evidence strength: Strong for increasing high-intensity exercise capacity and supporting gains from training. Evidence is much stronger for creatine monohydrate than for alternative forms.
• Dose studied: A common maintenance protocol is 3 to 5 g daily. A loading protocol of about 0.3 g/kg daily for 5 to 7 days, divided across the day, can saturate muscle more quickly, followed by 3 to 5 g daily. Loading is optional.
• Timing studied: Consistency matters more than a narrow pre-workout window. Without loading, muscle stores rise gradually over several weeks.
• Likely benefit: The clearest use is repeated short, intense efforts such as resistance training and sprint work. Changes in lean mass occur alongside training and may include early water retention.
• Limitations: Responses vary, and much of the research involves healthy, active adults. Creatine is not a substitute for adequate energy, protein, or training.
• Safety: Gastrointestinal discomfort can occur, particularly with large single doses. People with kidney disease, abnormal kidney results, or medications that affect kidney function should ask their clinician whether creatine is appropriate.

Sources: ISSN position stand on creatine and a 2025 systematic review of creatine and kidney function.

Beta-alanine: a daily loading ingredient for specific hard efforts

Bottom line: Beta-alanine is most relevant to sustained high-intensity work where muscle acidity contributes to fatigue. The evidence does not support treating it as an instant energy ingredient.

• Evidence strength: Moderate and task-specific. A sports-nutrition position stand found the clearest effects in exercise lasting about 1 to 4 minutes.
• Dose studied: Research commonly uses 4 to 6 g daily for at least 2 to 4 weeks. Dividing the daily amount can reduce tingling.
• Timing studied: Daily exposure matters. Taking it immediately before a workout is not required for the loading effect.
• Likely benefit: It may improve capacity during repeated or sustained high-intensity efforts. It is less compelling for a single brief maximal lift or steady, low-intensity exercise.
• Limitations: The benefit depends on the exercise test. Studies do not establish that everyone needs beta-alanine or that feeling tingling means performance improved.
• Safety: Temporary tingling, called paresthesia, is the best-known side effect. It is dose-related and can be reduced with divided doses or sustained-release formulations.

Source: ISSN position stand on beta-alanine.

Citrulline malate: possible small acute benefit, with uncertainty

Bottom line: Citrulline malate may help some people complete a few more repetitions during resistance exercise, but the average effect is small and the evidence is less settled than for caffeine or creatine.

• Evidence strength: Mixed. A meta-analysis of eight small placebo-controlled studies found a small improvement in repetitions to fatigue, while a critical review found equivocal results and concerns about supplement composition.
• Dose studied: The meta-analysis evaluated 6 to 8 g protocols.
• Timing studied: Studies generally provided it 40 to 60 minutes before resistance exercise.
• Likely benefit: A small increase in muscular endurance during high-intensity resistance sessions is possible. This does not establish a meaningful benefit for every workout or sport.
• Limitations: The meta-analysis included 137 participants, mostly strength-trained men. Products can differ in their citrulline-to-malate ratio, so equal label weights may not contain equal citrulline.
• Safety: Gastrointestinal discomfort can occur. Evidence is not sufficient to assume that higher doses work better or are appropriate for everyone.

Sources: citrulline malate meta-analysis and critical review of citrulline malate research.

Dietary nitrate: promising for some tasks, inconsistent overall

Bottom line: Nitrate-rich foods or beetroot products may improve some exercise-capacity outcomes, but results depend on the population and test. This is not a universal endurance booster.

A 2025 umbrella review covering 20 systematic reviews found improvements in time-to-exhaustion, muscular endurance, and some power outcomes, but no significant improvement in several other measures. It also rated most included reviews as low or critically low quality. An earlier meta-analysis found a benefit for time-to-exhaustion but not time-trial performance. Lasting longer in an open-ended lab test is not the same as finishing a race faster.

Sources: 2025 umbrella review of nitrate and performance and meta-analysis of endurance outcomes.

What to skip or scrutinize

Proprietary blends and undisclosed stimulant totals

A blend is not automatically ineffective, but a label that hides individual amounts prevents you from comparing the formula with research and calculating total stimulant intake. Count caffeine from every named source, including guarana or other caffeine-containing extracts. More stimulation is not the same as better performance.

DMAA and DMHA

Do not use products listing DMAA, methylhexanamine, geranium extract as a stimulant, DMHA, or octodrine. The FDA says DMAA is not a dietary ingredient and advises consumers not to buy or use products containing it. The agency also considers DMHA an unsafe food additive in dietary supplements. These ingredients continue to appear in enforcement actions and may be undeclared.

Sources: FDA information on DMAA and FDA information on DMHA.

BCAAs when protein intake is already adequate

BCAAs provide three essential amino acids, but muscle protein synthesis requires all essential amino acids. A review of the human evidence concluded that BCAAs alone do not provide a complete anabolic response. A pre-workout BCAA product should not be treated as equivalent to adequate total protein or a complete essential-amino-acid source.

Source: review of BCAAs and muscle protein synthesis.

Ingredients supported mainly by sensation or marketing

Tingling, flushing, and feeling stimulated do not prove that a workout improved. Be cautious when a formula emphasizes dramatic promises or sensations but does not disclose amounts or connect each ingredient to an outcome supported by human trials.

How pre-workout ingredients can affect health measurements

Supplements can change a measurement without answering whether the supplement is suitable for you. Testing may provide context, but it does not diagnose supplement safety or predict performance benefit.

• Creatinine and eGFR: Creatine can produce a modest rise in serum creatinine. Because many eGFR equations use creatinine, calculated eGFR may change even when measured filtration has not. A 2025 meta-analysis found a small increase in serum creatinine without a significant change in GFR, but it does not establish safety for every person or duration. Tell the clinician interpreting results about creatine use, dose, and timing.
• Glucose: Acute caffeine intake can temporarily reduce insulin sensitivity. Meta-analyses observed this in healthy participants and in small trials involving people with diabetes. That does not mean caffeine causes diabetes, but use and timing can be relevant context for a glucose result.
• Heart rate and blood pressure: Caffeine and stimulant combinations can raise heart rate or blood pressure in some people. Response depends on dose, sensitivity, other ingredients, and medications. A single reading cannot determine whether a supplement caused the change.
• Sleep: Caffeine can shorten sleep and reduce sleep efficiency. Effects vary by dose, timing, and person.

Sources: creatine and kidney-function meta-analysis, meta-analysis of caffeine and insulin sensitivity, systematic review in people with diabetes, FDA caffeine guidance, and caffeine and sleep meta-analysis.

How to evaluate a pre-workout label

1. Start with the outcome. Decide whether you want an acute alertness effect, support for repeated high-intensity training, or something else.
2. Separate acute from loading ingredients. Caffeine and citrulline are studied around a session. Creatine and beta-alanine depend mainly on consistent use.
3. Read the full stimulant total. Include caffeine from drinks, medications, and every supplement used that day.
4. Reject hidden doses. A proprietary blend prevents a meaningful evidence and safety comparison.
5. Look for independent certification. Programs such as NSF Certified for Sport or Informed Sport can reduce, but not eliminate, contamination or banned-substance risk. Certification does not prove that a product works.
6. Treat sleep and symptoms as outcomes. Seek medical help for severe symptoms such as chest pain, fainting, or trouble breathing. Discuss recurring palpitations, marked anxiety, or sleep disruption with a clinician.

The shortest effective label is often easier to evaluate than a formula with a dozen overlapping ingredients. Choose based on the specific outcome, evidence for that outcome, total exposure, and health context, not on how intense the product feels.