What is pre-workout? What's inside, and caffeine-free versions

Pre-workout literally means "before training": a supplement that mixes several ingredients to take before exercise. The common ones are caffeine, beta-alanine and citrulline. Each has a different level of evidence, and some products abroad have been found to contain banned stimulants. This page covers what is in the tub, what the research says, and how to read the label before buying.

Caffeine, the main ingredient

The ISSN's 2021 position stand concludes that caffeine consistently improves exercise performance at 3–6 mg per kg of body weight. The minimal effective dose may be as low as 2 mg/kg, and it is most often taken about 60 minutes before exercise. For a 60 kg person that is about 180–360 mg. Benefits include muscular endurance, movement speed, strength, sprinting, jumping and throwing, with small to moderate effects; aerobic endurance shows the most consistent benefit. The ISSN also notes that caffeinated energy drinks and pre-workout supplements have been shown to improve both anaerobic and aerobic performance.

Very high doses, such as 9 mg/kg, carry a high risk of side effects and are not needed for a performance effect. The U.S. Food and Drug Administration (FDA) says that for most adults 400 mg a day is not generally associated with negative effects, though sensitivity varies. Too much can bring a fast heartbeat, raised blood pressure, insomnia, anxiety, jitters, nausea or headache. Count caffeine from coffee, tea and energy drinks on the same day too.

Beta-alanine, the tingle

The ISSN's 2015 position stand says beta-alanine raises muscle carnosine, which acts as a pH buffer inside the cell. The recommended amount is 4–6 g a day in doses of 2 g or less, taken for at least 2–4 weeks before it shows an effect, and it helps most in hard efforts lasting about 1–4 minutes. In other words, beta-alanine works by building up daily, not from a single scoop before training.

The only reported side effect is tingling of the skin (paresthesia), which smaller divided doses such as 1.6 g, or a sustained-release formula, can reduce. The ISSN says it currently appears safe in healthy people at recommended doses.

Citrulline and nitric oxide

Citrulline is an amino acid the body can make itself, found in large amounts in watermelon. The body converts it to arginine, and it is a precursor for nitric oxide, which is why pre-workout formulas often include it. A 2022 meta-analysis by Viribay and colleagues pooled 10 trials with 173 participants and found no significant benefit for aerobic exercise performance. Single doses of 1–12 g taken 1–3 hours before exercise did not help; taking it for 6–16 days showed a trend that was not significant. The most common dose in these studies was 6 g.

With or without caffeine

Of these three, caffeine is the only one with evidence of an effect on the day you take it. A caffeine-free formula usually leaves beta-alanine, which needs weeks of daily use, and citrulline, whose aerobic evidence is weak, so don't expect the same feeling.

Caffeine-free suits people who are sensitive to caffeine, train in the evening and then sleep badly, or already get plenty from coffee. The ISSN says effects on sleep and anxiety differ between people, partly because of genetics and habitual caffeine use.
The FDA advises people who are pregnant, trying to become pregnant, breastfeeding, who have certain conditions or take certain medications to talk with a doctor about caffeine.

Banned stimulants such as DMAA

The FDA says supplements containing DMAA are illegal. DMAA raises blood pressure and strains the heart, with effects ranging from shortness of breath to heart attack, seizures and neurological and psychological conditions, and the risk is higher when it is combined with other stimulants such as caffeine. Labels may use other names, such as methylhexanamine, geranamine, dimethylamylamine, 1,3-dimethylpentylamine or 4-methyl-2-hexanamine, and "geranium extract" or "Pelargonium graveolens extract" on a label may also mean DMAA.

A recent case: KCTV5 reported on 11 October 2026 that Leader Formulas LLC recalled Rapture Pre-workout in three flavours (Rainbow Twist, Electric Lemonade and Berry Mojito), sold in the US from January to May, after FDA testing found DMAA. The maker reported no adverse reactions.

Check the label before buying in Thailand

Thai FDA number: check it in the health product number search on oryor.com, the ORYOR Smart Application, LINE @FDAthai or the Thai FDA hotline 1556. Enter every letter and digit, then check that the Thai and English product names, trade name and company match the label. A number does not guarantee every batch, because the Thai FDA samples products after registration.
Amount per scoop: a good label lists caffeine, beta-alanine and citrulline separately in mg or g. If it only gives a blend total, you cannot compare it with the research doses above.
Ingredient list: look for any of the DMAA names above.

See pre-workout in our store. If the goal is building muscle, the better-supported factor is total daily protein; compare options on the whey protein page and read what is creatine.