How much caffeine is too much? For most healthy adults, official advice is up to 400 mg a day, about four mugs of instant coffee, and no more than about 200 mg at once. Studies that give people a measured dose find that anxiety ratings rise as the dose gets bigger, and some people feel it at amounts well below those figures.
This post covers the official numbers, what the studies found on caffeine and anxiety, why the same cup lands differently on different people, and how to count your own day.
Contents
- The short version
- Recommended caffeine intake per day: the official numbers
- Can caffeine cause anxiety? What the studies found
- Why the same dose lands differently
- One cup can be your whole 200 mg
- If you already live with an anxiety or panic condition
- What cutting back looks like in the research
- How to find your own number
The short version
Up to 400 mg a day from all sources, and about 200 mg at a time, are the levels the European Food Safety Authority treats as no safety concern for healthy adults. They are ceilings, and they do not cover everyone. In lab studies of light caffeine users, 50 mg did not raise anxiety ratings, 150 mg did in some people, and 450 mg did in most. Daily drinkers feel less of the anxious effect than people who rarely have caffeine. One coffee-shop drink can hold more than 200 mg by itself, so the biggest single drink in your day matters as much as the total.
Recommended caffeine intake per day: the official numbers
The Food Standards Agency says that for most people, up to 400 mg of caffeine a day is unlikely to cause adverse effects. It bases that on the European Food Safety Authority (EFSA) opinion from 2015. The same page adds that people who are sensitive to caffeine at low doses, or who have underlying health conditions, may get side effects such as jitteriness, anxiety or difficulty concentrating (FSA, 2024).
EFSA gives two more figures, both for healthy adults and both counting every source of caffeine (EFSA):
- Up to 400 mg a day. With the NHS figure of about 100 mg for a cup of instant coffee, that is about four mugs.
- Single doses up to 200 mg, about 3 mg per kilogram of body weight. That is about two mugs at once.
- A single dose of 100 mg may affect sleep in some adults, particularly close to bedtime. We covered that in why your afternoon coffee is keeping you awake.
Two more details matter here. Pregnancy has its own, lower figure of 200 mg a day, which we went through in our pregnancy post. And EFSA's assessment does not cover people affected by a disease or medical condition, or people taking caffeine with medicines (EFSA explainer, 2015).
400 mg is where regulators found no safety concern for healthy adults. It is a ceiling, and a poor target.
Can caffeine cause anxiety? What the studies found
In studies where researchers hand people a measured dose, yes: anxiety ratings go up, and they go up more as the dose rises.
The clearest dose test comes from a 2008 trial. It gave 102 healthy adults capsules of 0, 50, 150 and 450 mg of caffeine on four separate days, with nobody knowing which was which. All of them normally had less than 300 mg a week, which is about three mugs of instant. The 50 mg dose did not raise anxiety ratings. The 450 mg dose, a little over four mugs at once, raised them in most people (Childs et al., 2008). The 150 mg dose is where the answer depended on who was taking it, and the next section picks that up.
A 2024 meta-analysis pooled eight articles and 546 healthy people. Overall, caffeine raised anxiety scores. Splitting the studies by dose, the authors found a moderate rise at lower doses and a much larger one at higher doses (Liu et al., 2024).
That result has limits:
- The studies measured anxiety on different scales, and the results varied widely between studies. The authors made the dose split after the fact, to explain that variation.
- Most of the studies gave one dose in a lab session, such as a 400 mg capsule or a can or two of energy drink, and asked about anxiety within the next hour or so. One was a survey of middle school students.
- So the "400 mg" in that paper is the amount in a single study session. That is a different measure from EFSA's 400 mg across a whole day, and the two should not be read as one number.
The pattern fits the lab trials. More caffeine at once means more anxiety and jitteriness on average, and some people react at lower doses than others.
Why the same dose lands differently
People differ
In a 2003 study, 94 healthy people who rarely had caffeine took 150 mg. People with certain variants of one gene reported bigger rises in anxiety than people without them (Alsene et al., 2003). A later study of 379 people, using 100 mg and then 150 mg, found the same thing (Rogers et al., 2010). You cannot read your own result into that. What it shows is that two people can drink the same cup and feel it differently.
Daily drinkers feel less of it
That 2010 study also compared people who drank little caffeine with people who drank a moderate or high amount. The regular drinkers had a smaller anxiety response, whatever their genes. The authors wrote that substantial tolerance develops to the anxiety effect of caffeine.
A 2013 study of 369 people found the other side of this. In people who normally had little caffeine, a rise in jitteriness cancelled out the gain in alertness from 100 mg and then 150 mg. In regular drinkers, caffeine did improve alertness, but those drinkers had also lost alertness when their usual caffeine was withheld. We cover that in why caffeine stopped working (Rogers et al., 2013).
It stays in you for hours
Caffeine's half-life is about 6 hours for most adults, anywhere from 2 to 10. A cup at 3pm is still about half there at 9pm. If you feel on edge in the evening, it is worth looking at what you had in the afternoon. The curve is in how long caffeine stays in your system.
If you feel on edge at your usual amount, that fits what the studies show. It is worth noticing, and there is nothing to be embarrassed about.
One cup can be your whole 200 mg
Most people count cups, and cups are not equal.
| Drink | Caffeine | In mugs of instant |
|---|---|---|
| Dark chocolate, 50 g bar | under 25 mg | a quarter of a mug |
| Can of cola | 40 mg | under half a mug |
| Cup of tea | 75 mg | three quarters of a mug |
| Energy drink, 250 ml can | 80 mg | just under 1 mug |
| Cup of instant coffee | 100 mg | 1 mug |
| Cappuccino, Starbucks (354 ml) | 89 mg | just under 1 mug |
| Cappuccino, Pret (355 ml) | 180 mg | nearly 2 mugs |
| Cappuccino, Caffè Nero (355 ml) | 221 mg | over 2 mugs |
| Cappuccino, Greggs (327 ml) | 235 mg | over 2 mugs |
| Cappuccino, Costa (332 ml) | 325 mg | over 3 mugs |
The first five rows are NHS and FSA figures. The NHS adds that filter coffee and coffee from coffee shops can contain more than instant (NHS). The cappuccino rows are the chains' stated figures as listed by Which? in August 2026, for cappuccinos of about 330 to 355 ml. Three of the five go past 200 mg on their own, and a Costa cappuccino is more than three mugs of instant in one go. The chain-by-chain detail is in how much caffeine is in high street coffee.
Even the same drink varies. A lab test of 20 espressos from high street coffee shops found a sixfold range. The strongest single espresso held 322 mg (Crozier et al., 2012). Asking for one shot fewer, or a size down, is the quickest way to bring a cup under 200 mg.
Adding up a day
The total is where most people lose track, because the small items add up without feeling like much. Take a day with two mugs of instant, two cups of tea, a can of cola and a small energy drink. No coffee shop is involved, and the day comes to 470 mg.
If you already live with an anxiety or panic condition
The studies above are mostly on healthy people. People with panic disorder are a different case.
- A 2022 review of ten trials found that 51% of people with panic disorder had a panic attack after a challenge dose of 400 to 750 mg, usually 480 mg. In the healthy comparison groups it was 1.7% (Klevebrant and Frick, 2022).
- A 2025 trial tested a lower dose. 150 mg did not raise anxiety ratings in 29 people with panic disorder or in 53 people without it, though it raised measures of arousal and avoidance in both groups (Hoppe et al., 2025).
The NHS page on generalised anxiety disorder tells people not to drink lots of coffee, tea, cola or energy drinks, because the caffeine can disrupt sleep and make anxiety harder to control (NHS). If caffeine and anxiety is a worry for you, talk to your GP or pharmacist. We cannot tell anyone why they feel the way they do.
What cutting back looks like in the research
There is one recent randomised trial of caffeine reduction. It followed 109 adults who wanted to cut down and who had symptoms they linked to caffeine. Over six weeks, with a written guide, their intake fell from about 565 mg a day to about 233 mg. Their scores for sleep, anxiety, reflux and diarrhoea all improved (Knerr et al., 2026).
The limits matter. The people chose to take part because they wanted to cut down, the control group was a waiting list rather than a placebo, and everyone knew which group they were in. So the trial shows that people can reduce their intake with a plan. It cannot show that the cutting caused the improvement, and we did not find a blinded trial that has tested it.
Stopping suddenly has its own cost. Withdrawal symptoms start 12 to 24 hours after the last dose and usually last 2 to 9 days. They can appear even from 100 mg a day (Juliano and Griffiths, 2004). The hour-by-hour picture is in our withdrawal timeline.
How to find your own number
You do not need a lab for this.
- Write down everything caffeinated you had yesterday and add it up, using the table above. Count tea, cola, energy cans and chocolate too. The caffeine calculator does the sum in about a minute and shows how much is still in you at bedtime.
- Mark any single drink over 200 mg.
- Note the time of your last drink of the day, and any time you felt jittery or on edge. Look for a pattern, such as one big cup that comes before it.
- If your own limit sits below 400 mg, yours is the one that counts.
The exercise needs no target and no change to your day. You are only getting the sum.
If you would rather follow a plan
The Uncaffed 30-day reset kit steps your caffeine down on a fixed schedule:
- Reset takes you from 160 mg a day to none over 20 days, five days at each step, with L-theanine alongside.
- Flow has no added caffeine and runs for all 30 days.
- For the 30 days, the capsules are your only caffeine. Decaf, herbal tea and rooibos keep the ritual going.
Heavy caffeine user? If you have more than about 400 mg a day from all sources, try to cut down a little before you start. Dropping straight to the kit's starting level can be a big change if you're not prepared for it. Not sure how much you have? The calculator adds it up. Everyone else can start straight away.
Preorders are open. Kits ship 30 November, UK only. The quiz helps you find your starting point, and the science page explains how the steps were chosen. The kit is not for under-18s or anyone pregnant or breastfeeding.
