There's a clean number for this, which is rare for anything health-related. For most healthy adults, up to 400mg of caffeine a day is considered safe by European food-safety authorities, with single doses up to about 200mg at a time.
The catch is that 400mg is easier to reach than people expect, and the dose that's "fine" for one person can leave another jittery and awake at 2am. So let's put real numbers to it.
What 400mg actually looks like
Caffeine content varies a lot by drink, brewing method, and size, but here's a rough guide to the common sources:
- Brewed coffee (large mug): 95–165mg
- Espresso (single shot): 60–80mg
- Energy drink (standard can): 80–150mg
- Black tea: 40–70mg
- Green tea: 30–50mg
- Cola (can): 30–40mg
Add a couple of those together and you climb fast. Two large coffees in the morning and an afternoon energy drink can put you near or past 400mg before dinner — and that's before counting any pre-workout, dark chocolate, or that third "I'll just have one more" cup.
Rather than doing that arithmetic in your head, you can run it: our caffeine calculator has these drinks as presets, adds up your day against both the 400mg and 200mg reference figures, and shows you what's still in your bloodstream at bedtime. It won't tell you your personal limit — nothing can — but it will tell you where you actually stand.
Note the ranges, because they're the real problem. A "coffee" is not a dose, it's a spread — and if you can't put a number on what you took, you can't tell how close you are to the ceiling. That's the case for a declared dose over a guessed one, and it's the whole reason this arithmetic is so slippery.
This is the part people miss. Nobody sets out to overdo caffeine. It accumulates across a day in small, unremarkable steps, and because the lift fades long before the caffeine clears, it doesn't feel like it's adding up.
What "too much" feels like
Your body is fairly good at telling you when you've crossed the line. The common signs of too much caffeine:
- A racing or pounding heart
- Jitters or shaky hands
- Anxiety or a wired, restless feeling
- Trouble sitting still or concentrating, ironically
- An upset stomach
- Trouble falling asleep, or worse sleep even when you do
If you regularly feel anxious and wired rather than focused, the problem often isn't stress — it's the fourth coffee. Caffeine and anxiety feel remarkably similar from the inside, and past a certain dose, caffeine simply produces the physical symptoms of anxiety directly.
The single-dose limit matters too
The 400mg figure is a daily total, but there's a second number worth knowing: roughly 200mg in one sitting is the point above which most people start feeling the downsides rather than the benefits.
This is why a giant pre-workout scoop or a triple-shot energy drink can feel bad even if your daily total is reasonable. A big single hit spikes hard, and what goes up that fast tends to crash just as hard.
For reference, a sensibly dosed supplement sits inside these limits on purpose. Aurora Flow's daily dose contains 180mg of caffeine — under the 200mg single-dose threshold, and printed on the label rather than buried in a blend. That's not an accident; it's what dosing something properly looks like instead of maxing it out and hoping nobody checks.
Who needs to be more careful
The 400mg average doesn't apply to everyone. Some people should aim lower:
Pregnant or breastfeeding: guidance typically drops to around 200mg a day, since caffeine clears much more slowly during pregnancy. Check with a doctor.
Caffeine-sensitive people: if you're a slow metaboliser, even 200mg total can disrupt your sleep. Listen to your body over the chart.
Anyone with a heart condition or anxiety disorder: worth a conversation with your doctor about your personal ceiling.
Teenagers: recommended limits are lower than for adults.
So how much should you have?
There's no universal answer, but a sensible framework: stay under 400mg total across the day, keep any single dose around or below 200mg, and pay more attention to how you feel than to the chart. If you're sleeping badly or feeling wired instead of focused, you're over your personal limit regardless of what the average says.
The goal was never to maximise caffeine. It's to take enough to get the focus benefit without tipping into the jittery, anxious, sleepless territory on the other side. More is not better here — past a point, more is just worse.
The short version
For most healthy adults, up to 400mg a day and around 200mg per dose is the safe zone. It adds up faster than you'd think across coffees, teas, and energy drinks. If you feel wired, anxious, or you're sleeping badly, that's your sign you're over the line — and the fix is less, not another cup to push through it.
Aurora Flow Energy Complex: caffeine 180mg, guarana extract 60mg, taurine 400mg, vitamin C 560mg per daily dose. Four ingredients, every amount disclosed, no proprietary blends. See the full product, or read our guide to caffeine capsules and how to read the label.
Food supplement — not a substitute for a varied, balanced diet and a healthy lifestyle. Not recommended for children or pregnant women. Do not exceed the recommended daily dose. Vitamin C contributes to the reduction of tiredness and fatigue and to normal energy-yielding metabolism. No health claims are authorised in the EU for caffeine, guarana or taurine, and none are made in this article.