How much energy drink is too much?

It would be easy to answer this with a rule: one a day is fine, two a day is too much. Reality is a little more complicated than that.

It matters how big the can is, how much caffeine is in it, whether you drink coffee alongside it, and how your own body reacts to it.

The difference between a 250 ml energy drink and a half-litre can is not just that the bigger one takes longer to finish. The larger size usually means twice the caffeine, too.

Count the caffeine first, not the cans

It is easy to fall into the trap of tracking only how many cans you drink.

I only have one a day.

That sounds reassuring, but it matters a great deal whether that one drink is 250, 500 or even 568 millilitres. Caffeine content also varies between products, so it is always worth reading the amount printed on the can.

For an energy drink at 32 milligrams of caffeine per 100 millilitres — common across Europe — the numbers work out roughly like this:

• 250 ml: 80 mg of caffeine
• 330 ml: about 106 mg of caffeine
• 500 ml: 160 mg of caffeine

According to the European Food Safety Authority (EFSA), single doses of caffeine up to 200 mg generally raise no safety concern for an average healthy adult. For total daily intake, 400 mg is the amount that still raises no safety concern in most healthy adults.

It is important to understand that this is not a target.

Coffee counts too

Say you have a coffee in the morning, a half-litre energy drink at lunch, and another coffee in the afternoon.

Your daily caffeine intake might look roughly like this:

• morning coffee: about 80–100 mg
• 500 ml energy drink: about 160 mg
• afternoon coffee: another 80–100 mg

That is already 320–360 mg of caffeine, while it still feels like you only had “one energy drink”.

Caffeine is not only in energy drinks and coffee, either. It can be in tea, cola, chocolate, pre-workout powders, some supplements and even certain medicines. EFSA estimates that a 250 ml energy drink contains roughly 80 mg, an espresso roughly 80 mg, and a mug of filter coffee roughly 90 mg of caffeine. These are approximations, of course.

Cola counts as well — even if you never think of it as caffeinated

Many people treat cola as a plain soft drink, and leave it out of the count entirely when adding up their caffeine for the day.

Yet most regular and sugar-free colas contain caffeine.

A 330 millilitre can of Coca-Cola, for example, contains roughly 33–34 milligrams of caffeine. That is far less than an energy drink or a coffee, but it still adds to the daily total.

A glass of cola of about 250 millilitres works out to roughly 25 milligrams of caffeine. Have one with lunch and one with dinner and that is nearly 50 milligrams of extra caffeine you almost certainly never counted.

Here is a completely ordinary day:

• a morning coffee: about 80–100 mg
• a 500 ml energy drink: about 160 mg
• two glasses of cola: about 50 mg
• an afternoon coffee: another 80–100 mg

Altogether that can reach 370–410 milligrams of caffeine.

On its own, none of those drinks looks excessive. Together they can reach — or even pass — the 400 milligrams a day that is generally given as the upper limit for healthy adults.

So counting energy drinks alone is not enough. Coffee, cola, tea, pre-workout supplements and every other source of caffeine belong in the same total.

Sugar-free cola is not necessarily the answer here either. Having no sugar and almost no calories does not mean it has no caffeine.

So how many energy drinks a day is too much?

Using an energy drink with average caffeine content:

One 250 ml can a day

In caffeine terms this is still a relatively low amount for most healthy adults. It is worth watching whether you drink coffee alongside it, how much sugar the drink contains, and whether you actually need it every single day.

One 500 ml can a day

That is usually about 160 mg of caffeine. On its own it is still under the 200 mg single-dose figure, but one or two coffees can push your daily total up quickly.

Two 500 ml cans a day

That is around 320 mg of caffeine from energy drinks alone. Add coffee, tea or cola and 400 mg a day is easy to pass.

Three or more large cans a day

With most average products this can approach or exceed 400 mg of caffeine a day by itself. At this point there is not much to calculate: this counts as too much.

With higher-caffeine American energy drinks, or so-called energy shots, a single serving can contain considerably more. FDA figures show that the caffeine content of energy drinks varies enormously between products and sizes, which is why checking the label matters more than the size of the can or the name on it.

Less may already be too much for you

Official guidance applies to average, healthy adults. Individual sensitivity, however, varies widely.

Some people drink an energy drink in the afternoon and fall asleep without any trouble. Others feel restless after a single can in the morning.

Several things can change how caffeine affects you:

• body weight
• how used to caffeine you are
• how much you sleep
• stress
• a tendency towards anxiety
• medication you take regularly
• cardiovascular problems
• pregnancy
• the time of day you drink it

The FDA also notes that caffeine sensitivity, and the speed at which people break caffeine down, can differ significantly from person to person. That is why some people get unpleasant symptoms well below 400 mg.

Your body often signals before the numbers do

You do not have to wait until you cross an official threshold.

If you regularly notice the following, it is worth cutting your caffeine down:

• a racing heartbeat
• strong palpitations
• shaky hands
• inner restlessness
• heightened anxiety
• trouble falling asleep
• frequent waking at night
• stomach discomfort
• nausea
• headaches
• exhaustion in the afternoon or evening

The FDA links these symptoms to excessive caffeine consumption as well.

It is also worth noticing what happens on a day without an energy drink.

If you get a headache, feel irritable, struggle to concentrate, or feel unable to start the day without one, some degree of dependence has probably already developed.

That does not mean you have a serious addiction. It means caffeine has become part of how your day functions.

Timing matters too

Many people look only at the daily amount, when it also matters when you drink it.

According to EFSA, as little as 100 mg of caffeine may affect the length and quality of sleep in some adults, particularly when consumed close to bedtime.

That is roughly the caffeine in a smaller energy drink.

So an afternoon can may mean you fall asleep later, wake up more tired, and reach for another energy drink because of it. That is how a loop forms:

At that point the problem is often not simply that you drink too much caffeine. The energy drink has started to sustain the very tiredness that made you start drinking it.

Sugar-free energy drinks can be too much as well

A sugar-free version may have fewer calories and less sugar, but the caffeine is often identical to the regular version.

So switching from regular to zero can cut your sugar intake, while your caffeine consumption stays exactly where it was.

If the problem is poor sleep, palpitations, restlessness or being tired without a can, a sugar-free version alone does not solve it.

When is it worth cutting back?

Not only once you are on three or four cans a day.

It is worth cutting back if:

• you keep increasing the dose
• a smaller can is no longer enough
• you do not feel functional without one
• you regularly drink them in the afternoon or evening
• your sleep has got worse
• you often feel palpitations or restlessness
• you have tried to stop several times without success
• you are spending more and more on it
• you do not really enjoy it any more and drink it out of habit

“Too much”, then, is not only a quantity of caffeine.

You may still be under 400 mg a day on paper, while energy drinks have already taken on too large a role in your days.

You do not have to stop overnight

If you drink several energy drinks a day, going to zero tomorrow is not necessarily the best plan.

Cutting caffeine abruptly can cause headaches, fatigue, irritability and difficulty concentrating. That is why the FDA suggests regular consumers reduce their intake gradually.

As a start, it already helps if you:

• swap the half-litre can for a smaller one
• drop the second energy drink
• push the first can slightly later each week
• stop having caffeine in the afternoon
• write down exactly when and why the craving hits

The goal is not to do it perfectly. The goal is to gradually put you back in charge of your consumption, so an energy drink is not the thing deciding how your day starts or continues.

In short

For a healthy adult, a total daily caffeine intake under 400 mg generally raises no safety concern — which does not mean that is the ideal amount for everyone.

An average 250 ml energy drink can contain roughly 80 mg of caffeine, and a half-litre one roughly 160 mg.

With two large cans a day, one or two coffees can be enough to reach or exceed 400 mg. And if you sleep badly, your pulse races, you feel anxious, or you can barely function without one, a smaller amount is probably already too much for you.

The numbers are a useful handhold, but in the end what counts is what your own body is telling you.