Ingredient
Strong evidenceCaffeine
Also known as: caffeine anhydrous, 1,3,7-trimethylxanthine
The most reliable performance stimulant — effective for focus, output and perceived effort.
What it is
Caffeine is a natural stimulant and by far the most-studied performance aid in sport. It is the active ingredient that does the heavy lifting in most pre-workouts, fat-burners and energy products, and it is the reason a strong coffee before training feels the way it does.
How it works
Caffeine blocks adenosine, the brain chemical that builds up and makes you feel tired, so you perceive effort as lower and can push harder for longer. It reliably improves focus, alertness, endurance and strength output, which is why it is one of the few supplement ingredients with genuinely strong evidence behind it.
Effective dose
The effective range is roughly 3 to 6mg per kg of bodyweight, taken 30 to 60 minutes before training. For an 80kg person that is about 240 to 480mg. We heavily penalise products that pack more than 400mg into a single serving, because past that point side effects (jitters, racing heart, crashed sleep) tend to outweigh any extra benefit.
Safety and upper limit
Health bodies put the safe daily ceiling for most healthy adults at around 400mg from all sources. Tolerance builds quickly, sensitivity varies a lot between people, and caffeine within about 8 to 10 hours of bed can wreck sleep quality. If you train in the evening, a stim-free pre-workout is the smarter call.
Where you find it
Pre-workouts, fat-burners, energy drinks and some intra-workout formulas.
Top Pre-Workout picks
The highest-scoring products in the category where Caffeine matters most.
Frequently asked
How much caffeine should I take before a workout?
Around 3 to 6mg per kg of bodyweight, taken 30 to 60 minutes before training. We penalise pre-workouts that exceed 400mg per serving.
Is 400mg of caffeine too much?
400mg is roughly the safe daily ceiling for most healthy adults from all sources, so a single serving at that level leaves no room for coffee or other sources. We mark products above it down.
Does caffeine tolerance build up?
Yes, quite quickly. Many lifters cycle off for a week or two periodically, or keep the dose modest, to keep it effective.
Caffeine vs ...
Related guides
This page is educational and not medical advice. Doses are general guidance from the published research, not a personal prescription. Before starting any supplement that could affect a medical condition or interact with medication, speak to a qualified clinician.