Caffeine is a natural stimulant found in coffee, tea, cocoa, energy drinks, and many pre-workout supplements. It works mainly by blocking adenosine, a brain chemical that makes you feel tired, which increases alertness and energy.
What it does
Improves focus and reaction time — especially helpful for studying or work.
Boosts physical performance — increases adrenaline and helps muscles use fat for fuel. Common in pre-workout formulas.
Elevates mood by increasing dopamine and serotonin slightly.
Raises metabolism and may help with fat oxidation.
How long does it last
You start to feel it in about 15–45 minutes, and its effects can last 4–6 hours, depending on tolerance.
Common safe range
200–400 mg per day for most healthy adults (roughly 2–4 cups of coffee or 1–2 energy drinks).
Too much can cause jitters, anxiety, rapid heart rate, headaches, or sleep problems.
Good sources
Black coffee: 80–120 mg per cup
Espresso: 60–70 mg per shot
Green tea: 30–50 mg
Energy drinks: 80–300 mg per can
Dark chocolate: 20–40 mg per bar
Pre-workout: 150–350 mg per scoop
Best time to take it
Morning after waking to avoid disrupting sleep.
30–45 mins before training for performance.
Avoid within 6–8 hours of bedtime.
Who should be careful
People with anxiety, high blood pressure, or sleep problems
Teenagers and those mixing caffeine with alcohol
New users of stimulants or strong supplements
Pro tip
Cycling caffeine (e.g., taking breaks for a week every 6–8 weeks) helps reset tolerance so you continue getting benefits without escalating doses.
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