What is pre-workout, and is it safe?

What is pre-workout?

Pre-workout is a supplement, usually a flavoured powder mixed with water, that you take before exercise, most often for energy and focus. Most pre-workout supplements are built around caffeine. When researchers analysed the 100 best-selling pre-workouts on a US retailer's website in 2018, the average product had 18 ingredients, eight of them in a "proprietary blend" that didn't say how much of each was in it (Jagim and colleagues, 2019).

In the UK, pre-workouts are sold as food supplements. They don't need a licence or government approval, and the business selling one is responsible for making sure it's safe. The Food Standards Agency (FSA) notes there's no legal maximum for caffeine in a food supplement. Products with added caffeine above 150 mg per litre must carry the warning "Contains caffeine. Not recommended for children or pregnant women", with the caffeine content per serving.

What is in pre-workout?

The 2019 analysis found the same handful of ingredients in most products. The table shows how common each one was, the average amount per serving, and whether Great Britain allows any health claim for it.

Caffeine

Caffeine is the main stimulant. The International Society of Sports Nutrition (ISSN) position stand on caffeine says doses of 3 to 6 mg per kg of body weight have consistently improved exercise performance in studies, most often taken 60 minutes before, with the most consistent results in endurance exercise. For a 70 kg adult that's 210 to 420 mg. Several of its authors advise sports nutrition companies. There are no authorised health claims for caffeine in Great Britain.

Beta-alanine

Beta-alanine causes the tingle many people associate with pre-workout. In the research, people took 4 to 6 g every day for weeks to build up carnosine in muscle. The 2019 analysis noted the average 2.0 g serving was below the dose shown to work. Our beta-alanine guide covers dosage and the tingle.

Citrulline

Citrulline is an amino acid found in watermelon, sold as a supplement either as L-citrulline or as citrulline malate. A 2021 meta-analysis of eight small studies found that 6 to 8 g of citrulline malate taken 40 to 60 minutes before strength training let people do about 6% more repetitions than placebo (Vårvik and colleagues). A 2026 meta-analysis of 30 trials found a small effect overall, rated the certainty of the evidence as low to very low, and said reliable doses haven't been established (Wang and colleagues).

Creatine: is creatine a pre-workout?

Not really. Creatine works by filling the stores in your muscles over days or weeks of daily use, so the timing of a dose matters far less than taking it every day. The authorised claim in Great Britain is that creatine increases physical performance in successive bursts of short-term, high intensity exercise, with the benefit obtained at a daily intake of 3 g. The average pre-workout serving, 2.1 g, falls short of that. Our guide to how to take creatine covers the dose and timing.

Taurine

Taurine is an amino acid also found in energy drinks. A 2018 meta-analysis of ten studies, using 1 to 6 g taken once or daily for up to two weeks, found a modest positive effect on endurance tests (Waldron and colleagues). The studies were small, and taurine has no authorised health claims.

Some products also add niacin. The NHS says high doses of nicotinic acid supplements can cause skin flushes.

How much caffeine is in pre-workout, and how much is too much?

The average best-seller in the 2019 analysis had more caffeine in one scoop than the European Food Safety Authority (EFSA) single-dose level. EFSA found that, for healthy adults:

• single doses up to 200 mg (about 3 mg per kg) raise no safety concerns, including when taken less than two hours before intense exercise in normal conditions
• up to 400 mg a day from all sources raises no safety concerns, except in pregnancy
• 100 mg may affect sleep in some adults if taken close to bedtime

The NHS limit in pregnancy is 200 mg a day. EFSA's level for children and teenagers is 3 mg per kg of body weight a day.

The bigger risk is stacking. The NHS estimates 100 mg in a mug of instant coffee, 75 mg in a cup of tea and 80 mg in a 250 ml can of energy drink. A 250 mg scoop, two mugs of instant coffee and one energy drink comes to 530 mg. In the 2019 survey of regular users, 14% took two or more servings at once and 18% used pre-workout more than once a day (Jagim and colleagues). Our caffeine calculator adds up a day for you.

The FSA says serious effects, including a rapid heart rate, abnormal heart rhythms and seizures, have been seen at about 1,200 mg of caffeine, and that deaths have been reported where pure caffeine powder was measured wrongly.

Is pre-workout bad for you?

For a healthy adult taking one serving with a known amount of caffeine, the short-term studies haven't found much harm, but side effects are common and the long-term evidence is thin. A 2018 review found most safety studies lasted less than eight weeks (Harty and colleagues). In the 2019 survey of 872 regular users, 54% had experienced side effects, and women were more likely to report them.

Pre-workout side effects

The FSA lists these effects of high caffeine intake:

• jitteriness, nervousness, anxiety and irritability
• palpitations (a racing or irregular heartbeat) and restlessness
• nausea, sweating and tremor
• pins and needles, and possibly dizziness
• disturbed sleep

On top of those, beta-alanine causes tingling and niacin can cause flushing.

Banned stimulants in UK products

Some products contain stimulants that shouldn't be there. DMAA (methylhexanamine) is classed as an unlicensed medicine in the UK. The Medicines and Healthcare products Regulatory Agency (MHRA) first removed products containing it from sale in 2012, warned in 2017 that a significant number were still on sale in the UK, and links it to high blood pressure, tightening in the chest, strokes, heart attacks and death. UK Anti-Doping (UKAD) says DMAA is on the World Anti-Doping Agency prohibited list. DMHA (octodrine) was reintroduced in pre-workout and fat-burner products around 2016. A 2018 review led by University of Hertfordshire researchers found it had never been tested in a placebo-controlled trial, and reported side effects included high blood pressure, breathlessness and overheating (Catalani and colleagues).

If you compete in tested sport, UKAD's rule is strict liability: you're responsible for anything found in your sample, however it got there. It advises using batch-tested supplements only, checking batch numbers on the Informed Sport website, and warns that even a batch-tested supplement still carries some risk of containing a prohibited substance.

What is a non-stim or caffeine free pre-workout?

A non-stim (stim-free) pre-workout, also sold as a caffeine free pre-workout, leaves out caffeine and other stimulants, keeping ingredients like citrulline, beta-alanine and creatine. That avoids caffeine's effects on sleep and the risk of stacking it with coffee. It can still make you tingle if it contains beta-alanine, and doses are often below what the research used, so check the label for the grams of each ingredient per serving. Caffeine free on the front of the tub is worth checking against the ingredients list, because the FSA points out that ingredients such as guarana contain significant amounts of caffeine.

When should you take pre-workout?

For caffeine, the timing most used in research is about 60 minutes before exercise. The FSA says caffeine's effects can begin 15 to 30 minutes after you take it and last for several hours, so a late-evening session and a stimulant pre-workout can cost you sleep. Beta-alanine and creatine don't depend on timing: they work through daily use.

Is pre-workout good for running?

Caffeine is the ingredient with the most consistent running research behind it. The ISSN describes improvements in endurance of 2 to 4% across dozens of studies at 3 to 6 mg per kg. Beta-alanine research is mostly on hard efforts of one to four minutes, and its effect on events longer than 25 minutes is unclear. Creatine adds body weight, which runners may not want. If caffeine is what you're after, a single-ingredient product with the dose on the label tells you exactly how much you're taking. Coffee varies: the NHS notes that filter and coffee-shop coffee can contain more than the 100 mg in a mug of instant.

Is there a natural pre-workout?

A cup of coffee gives you caffeine, and a meal or snack with some carbohydrate beforehand gives you fuel. Our guide to what to eat before a workout has ideas. Beetroot juice is another option people try; our beetroot supplements guide looks at that research. "Natural" on a label doesn't mean low caffeine: the FSA points out that ingredients like guarana contain significant amounts.

What about pre-workout shots and gummies?

Whatever the format, the caffeine rules are the same. EFSA's levels, up to 200 mg at once and 400 mg a day for healthy adults, cover caffeine from all sources.

Pre-workout shots

A pre-workout shot is a small ready-mixed drink, so the caffeine is packed into a few millilitres. The FSA's labelling rule is set per litre: above 150 mg per litre, the warning "Contains caffeine. Not recommended for children or pregnant women" and the caffeine per portion are required. That line is crossed at just 9 mg of caffeine in a 60 ml shot, so any shot with a real dose is far above it. Count the whole amount towards your day. A shot with 150 mg plus a mug of instant coffee (about 100 mg, according to the NHS) comes to 250 mg, above EFSA's 200 mg single-dose level.

Pre-workout gummies

The FSA's caffeine guidance for supplements doesn't name gummies, so the safe levels above are your guide. Check whether the amounts on the label are per gummy or per serving, and how many gummies make a serving. Then compare the grams with the research doses earlier in this guide: 6 to 8 g of citrulline malate before training and 4 to 6 g of beta-alanine a day. Look at the sugar too, because the NHS says adults should have no more than 30 g of free sugars a day.

How do you choose the best pre-workout?

There is no single best pre-workout, because it depends on how much caffeine you tolerate. These label checks matter most:

• Caffeine per serving. Compare it with EFSA's 200 mg at once and 400 mg a day from all sources, and add your coffee, tea and energy drinks. EFSA says 100 mg near bedtime may affect sleep.
• Amounts for every ingredient. In the 2019 analysis, the average product had eight ingredients inside a "proprietary blend" with no amounts given.
• Doses that match the research. The 2019 analysis noted the average 2.0 g of beta-alanine per serving was below the dose shown to work. Citrulline is sold as citrulline or as citrulline malate, so check which one the grams refer to.
• A warning label. Products above 150 mg of caffeine per litre must carry the FSA wording.
• Batch testing. If you compete in tested sport, UKAD advises batch-tested products only and checking the batch number.

Our caffeine calculator adds up your day.

Where Natura fits

Natura doesn't sell a pre-workout. Some of our sport packs, in the Natura cabinet (coming soon) on our sport shelf, each pair two single-ingredient products with the dose on the label, including Daily Caffeine 100 mg, Daily Beta-Alanine 3.2 g, Daily Citrulline 6 g, Daily Taurine 1 g and Daily Creatine 3 g. Daily Creatine gives the 3 g a day at which creatine increases physical performance in successive bursts of short-term, high intensity exercise.