Why are you more tired after an energy drink?

We generally drink an energy drink because we are tired.

For the first half hour it really can seem to work. You are more alert, you concentrate more easily, and you may even feel up to the thing you would rather have put off.

Then a few hours later the next wave of tiredness arrives.

Sometimes stronger than before the energy drink.

Many people simply call this a caffeine crash. Behind it, though, there is not always one sudden “collapse”. Often several things happen at once:

• caffeine’s noticeable effect wears off,
• you notice your original tiredness again,
• regular caffeine intake means withdrawal symptoms can appear,
• the energy drink may worsen your next night’s sleep,
• and meanwhile you may still not have eaten, drunk or rested enough.

So an energy drink does not necessarily create new tiredness every time.

Energy drinks do not give you real energy

The name “energy drink” can be a little misleading.

Caffeine does not replace sleep, and it does not fill your body with new energy. What it primarily changes is your sense of alertness.

Over the course of the day a substance called adenosine gradually builds up in your body. Adenosine plays an important role in creating sleepiness and sleep pressure.

The longer you have been awake, the stronger the need for rest becomes.

By blocking adenosine receptors, caffeine reduces the feeling of sleepiness. That can make you seem more alert for a while, but your actual need for rest does not go away.

Picture covering up the fuel warning light on your car’s dashboard.

The warning being out of sight does not refill the tank.

Something similar can happen with caffeine. You feel the tiredness less, while your body may still badly need rest.

What happens as the caffeine wears off?

As the amount of caffeine in your system gradually falls, adenosine can act more freely again.

At that point you may notice again:

• the sleepiness,
• the drop in concentration,
• the lack of motivation,
• heavy eyelids,
• mental dullness.

It can easily feel as though the energy drink made you tired.

In reality you may simply be feeling again the tiredness the drink masked for a few hours.

If you only slept five hours to begin with, an energy drink will not leave you genuinely rested. You may function better for a few hours, but the lost sleep has not come back.

What is a caffeine crash?

A caffeine crash is not a precise medical diagnosis. It is more an everyday term for the state where, a few hours after caffeine, your alertness drops sharply and you feel more tired.

It can show up as:

• afternoon drowsiness,
• difficulty concentrating,
• irritability,
• wanting another energy drink,
• a headache,
• low spirits.

Not everyone experiences it the same way.

It is also possible that the unpleasant feeling is not caused by the caffeine wearing off, but by the next usual dose being late.

Regular caffeine intake can lead to physical adaptation. As caffeine levels fall, withdrawal symptoms can appear — commonly tiredness, drowsiness, reduced alertness and worse concentration.

It may not be lifting you up, only ending withdrawal

This is one of the most interesting parts of regular caffeine use.

When you first start drinking energy drinks you may genuinely feel a more dramatic stimulant effect.

Over time, though, the body can adapt to a regular caffeine supply. The same amount becomes less noticeable, so you may move to a bigger can or several doses a day.

Meanwhile, without caffeine, you may feel increasingly tired, dull or irritable.

When you drink the next energy drink, those symptoms ease. That makes it look as though the drink gave you new energy.

In reality it may partly have just brought you back to the level you had come to experience as normal.

In research, briefly stopping caffeine increased feelings of fatigue, sluggishness and exhaustion while reducing energy and alertness. Even a smaller dose of caffeine can temporarily relieve those withdrawal symptoms.

That is how this loop can form:

1. you take caffeine regularly,
2. your body adapts,
3. you feel more tired between doses,
4. you drink an energy drink,
5. you feel better,
6. so it feels like you need it.

Is the sugar causing the sudden tiredness?

Sugary energy drinks can contain a significant amount of sugar, so we often blame every subsequent slump on a “sugar crash”.

Reality is more complicated than that.

A sugary drink can raise blood sugar quickly, after which the body produces insulin to regulate it. Some people then experience hunger, weakness or dullness.

That does not mean sugar is definitely behind every post-energy-drink slump, though.

A similar feeling can follow a sugar-free energy drink, because:

• the caffeine wears off,
• the original tiredness returns,
• caffeine withdrawal can appear,
• or you simply slept too little.

So switching to a zero energy drink may cut your sugar intake, without necessarily changing the caffeine loop at all.

Energy drinks can mask hunger too

You may be tired because you have not eaten for hours.

The caffeine and strong taste of an energy drink can distract you from that briefly. And the sugary version can provide some usable energy quickly.

But you still have not had a proper meal.

A few hours later you may get:

• hunger,
• weakness,
• trouble concentrating,
• irritability,
• a craving for something sweet or another energy drink.

It is easy at that point to believe the first energy drink “ran out”, so you need another.

A proper breakfast or lunch might well help more.

Before you open the next can, it is worth thinking through:

• When did you last eat?
• Did that meal have protein and carbohydrate?
• Did you replace breakfast with an energy drink?
• Have you had any proper fluid today?

Dehydration can look like a caffeine crash

Tiredness, headaches and trouble concentrating are not only caffeine-related symptoms.

They can also appear when you drink too little.

A caffeinated drink is still fluid, so the simple claim that an energy drink “does not hydrate you at all” is not true. It is still not a good idea to drink almost nothing but energy drinks, coffee and cola all day, though.

Your fluid intake can easily fall short if:

• you work in the heat,
• you train,
• you sweat a lot,
• you forget to drink water,
• and the energy drink is suppressing your sense of tiredness meanwhile.

Before having more caffeine, drink a large glass of water and wait a few minutes.

It will not always be the answer, but it is easy to check.

Often the biggest problem is sleep

Tiredness after an energy drink is not only caused by that particular can wearing off.

Caffeine later in the day can also worsen your night’s sleep.

According to EFSA, as little as 100 mg of caffeine may affect the duration and pattern of some adults’ sleep, particularly when consumed close to bedtime. That is roughly the caffeine range of a smaller energy drink.

The sleep loop can look like this:

1. you are tired, so you drink an energy drink,
2. you have another in the afternoon or evening,
3. you fall asleep, but your sleep is less restful,
4. you wake more tired the next day,
5. so you have caffeine earlier and in larger amounts,
6. and by evening there is caffeine in your system again.

After a while you are no longer surviving one bad night.

The caffeine and the poor sleep can be sustaining each other.

Can you fall asleep? Your sleep can still be worse

Plenty of people say:

Caffeine does not affect me, I fall asleep right away after an energy drink.

Falling asleep, however, is only one part of sleep.

Caffeine can affect:

• total sleep time,
• night-time waking,
• how deep your sleep is,
• how continuous your sleep is,
• how rested you feel in the morning.

So you may not toss and turn for hours and still have a less restful night.

The next day you may need another energy drink, without ever connecting the tiredness to the previous day’s caffeine.

Caffeine’s effect on sleep depends on the amount, the timing and individual sensitivity too.

Why are you always tired in the afternoon?

Some dip in afternoon energy can be natural.

The problem starts when you answer every afternoon slump automatically with an energy drink.

Behind it there may be:

• too little or poor-quality sleep,
• too heavy a lunch,
• a skipped meal,
• too little fluid,
• hours of sitting,
• mental exhaustion,
• your morning caffeine wearing off,
• withdrawal before the next dose.

The solution is not the same for all of them.

If you are sleepy, you may need sleep. If you are hungry, you need to eat. If you have been sitting for hours, a short walk can help. And if you want an energy drink at the same time every day, a strong habit may simply have formed.

An energy drink can briefly mask any of those.

It will not necessarily solve them.

Why do you want another one?

The tiredness after the first can easily triggers the next.

The reasoning is simple:

The last one has worn off, I need another.

A second energy drink really can reduce the sleepiness again. In doing so, though, you:

• increase your daily caffeine,
• push back when the caffeine clears,
• raise the chance of worsening your sleep that night,
• and reinforce the adaptation further.

Because of that, the urge for an energy drink may arrive even earlier the following day.

So it is worth taking at least a ten to fifteen minute pause before the next can.

During that time:

1. drink water,
2. eat, if you have not eaten for hours,
3. stand up and move for a few minutes,
4. get some fresh air,
5. think about how much you slept.

After that you can still decide you need caffeine.

The difference is that you did not reach for it automatically.

Why does it not work like it used to?

If you take caffeine regularly, tolerance can develop over time.

That means the same amount produces a weaker effect. You pick a bigger can instead of the smaller one, or move from one a day to two.

The tolerance and physical adaptation that develop with regular caffeine intake have been described in research.

It can show up in several ways:

• you no longer feel the effect of the first can,
• you only get more alert after the second,
• you function noticeably worse without one,
• you have the first one earlier and earlier,
• you choose products with more and more caffeine.

At that point it is no longer clear that the energy drink is genuinely improving your baseline energy.

It may be that ever larger doses are needed just to avoid feeling the dip between them.

What can you do about the tiredness?

Do not immediately have another

Wait ten to fifteen minutes and try first to work out what you actually need.

Drink water

Not a miracle cure, but it helps rule out low fluid intake as a contributor to the headache or dullness.

Eat something

If you have not eaten for hours, a proper meal or a smaller, substantial snack can help more than another caffeinated drink.

Move for a few minutes

A short walk or a few minutes of movement can break the tiredness that comes from hours of sitting and monotonous work.

Watch the clock

If the next energy drink would fall in the late afternoon or evening, you may well be rescuing this afternoon at the cost of tonight.

Reduce gradually

If you drink several energy drinks a day, stopping abruptly can itself cause tiredness and headaches. A gradual reduction is generally easier to manage — the FDA also suggests tapering for people who take caffeine regularly.

A simple experiment to find the real cause

For one week, write down:

• when you drank the energy drink,
• what size it was,
• when you got tired again,
• when you ate,
• how much water you drank,
• how many hours you slept,
• whether you had other caffeine,
• whether you had another energy drink afterwards.

A pattern can emerge after just a few days.

You may find, for instance, that:

• the tiredness always follows a skipped lunch,
• you only need the second can after a badly slept night,
• you always wake worse the day after an afternoon energy drink,
• or the tiredness always arrives exactly before your usual next dose.

Once you know what triggers it, choosing the right solution is far easier.

When should you not blame the energy drink?

Persistent tiredness can have many causes.

It is not necessarily caffeine, poor sleep or a skipped meal alone behind it.

It is worth talking to a doctor if:

• you have been exhausted for weeks despite adequate sleep,
• you regularly fall asleep during the day,
• you get strong palpitations or an irregular pulse,
• you have chest pain,
• you get short of breath,
• you are often dizzy or you faint,
• the tiredness keeps getting worse,
• or it significantly interferes with your daily life.

Cutting caffeine can help, but a persistent health problem should not be treated as simply an energy drink crash.

In short

The tiredness that follows an energy drink can have several causes.

Caffeine does not remove real tiredness, it only reduces the feeling of it temporarily. As it wears off, the original sleepiness can come back to the surface.

With regular use, add to that:

• adaptation to caffeine,
• withdrawal before the next dose,
• too little food or fluid,
• sleep worsened by an afternoon energy drink,
• and a steadily growing amount of caffeine.

So the next can is not always a real solution.

You may be more alert again for a while, but you are also continuing the same loop.

An energy drink does not necessarily give you your energy back.

Sometimes it just postpones the tiredness by a few hours.