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Why Do Energy Drinks Make Me Tired? The 5 Main Culprits

Energy drinks can make you tired because of the excess caffeine and sugar, and they can easily disrupt your sleep. But you can stop that from happening.
Written by
Jeff Kahn, M.S., Rise Science Co-Founder
Reviewed by
Jamie Zeitzer, PhD, Rise Science Scientific Reviewer
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Why do energy drinks make me tired?

  1. The caffeine has worn off
  2. You've developed a caffeine tolerance
  3. You're experiencing caffeine withdrawal symptoms
  4. You're experiencing a sugar crash
  5. Energy drinks are causing sleep loss

To stop energy drinks making you feel tired, switch to sugar-free energy drinks (or other forms of caffeine), find out and stick to your caffeine cutoff time, reach for natural energy boosts, such as exercise, a nap, or a cold shower, and get enough sleep.

The RISE app can tell you when your unique caffeine cutoff time is and help you get more sleep. 80% of new RISE users have more energy within five days.

Energy drinks are meant to be the go-to thing to consume when you need to wake yourself up — they are called energy drinks after all. They’re meant to improve your physical performance, make you more alert, and generally perk you up. But all too often, they can actually leave you feeling even more tired than before you drank one. We’ve already covered why caffeine makes you feel tired, but energy drinks are a whole different beast. 

Below, we’ll dive into the science to find out what exactly energy drinks are doing to our bodies, why they can make us feel sleepy, and how you can fix the problem. 

Want to master the art of consuming caffeine? We’ve answered every question you could have about caffeine, sleep, and energy here.

How Do Energy Drinks Work?

Energy drinks are made up of a few ingredients designed to make you feel more awake and alert. 


We all know and love caffeine, and it works by temporarily stopping us from feeling sleepy. Adenosine is a chemical that builds up naturally in your body all the time you’re awake. It acts as a neuromodulator, depressing the central nervous system, and eventually reaching levels that make you feel drowsy. Caffeine comes in and binds to adenosine receptors in your brain, so the chemical can’t work on you, and you don’t feel its sleepiness effects. 

Many energy drinks contain 50 to 160 milligrams of caffeine, but some can even contain more than 500 mg of caffeine. To compare that to coffee, a single shot of espresso has about 63 mg of caffeine, whereas a cup of instant coffee ranges from 30 to 90 mg.


One thing that sets energy drinks apart from other caffeinated beverages is the sugar content, and you may see this on the label as high-fructose corn syrup or sucrose. It all depends on the brand, but one can of energy drink can contain around 54 grams of sugar, or about 13 teaspoons of sugar. 

The US Food and Drug Administration (FDA) recommends consuming no more than 50 grams of added sugar a day, based on a 2,000 calorie daily diet. The American Heart Association, however, recommends keeping sugar intake to just 36 grams (nine teaspoons) a day for men, or just 25 grams (six teaspoons) a day for women. 

How does sugar give you a burst of energy? Sugar is broken down by the body into glucose, which then travels through your blood to your muscles and organs where it’s converted into energy. Eating sugar also triggers the brain to produce the hormones dopamine and serotonin, so your mood improves along with your energy levels. 

Other Ingredients 

There are few other ingredients that go into energy drinks, including B vitamins, artificial sweeteners, taurine (an amino acid) and ginseng (a herbal supplement that can increase energy and memory).

There’s also guarana, a Brazilian plant native to the Amazon that’s known for its energy-boosting properties. In fact, guarana seeds contain more caffeine than any other plant in the world, and the plant also contains theobromine and theophylline, which are stimulants that interconvert into caffeine in the body. 

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Why Do I Get Tired After an Energy Drink?

So, you’d think with all that caffeine and sugar, you’d be bursting with energy after drinking an energy drink. But there are a few reasons why energy drinks may be having the opposite effect on you. 

1. Adenosine Has Caught Up With You 

As we explained above, caffeine blocks your adenosine receptors, but this is only temporary. Plus, adenosine continues to build in your system all the time you’re awake. So when the caffeine wears off, you can finally feel the effects of all the adenosine in your system. You can find out how long it takes for caffeine to wear off here. 

What’s more, research shows people who regularly consume caffeine have an increased number of adenosine receptors, meaning they can be more sensitive to the chemical and how sleepy it makes them feel. 

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2. You’ve Developed a Caffeine Tolerance

Maybe you used to be able to power through a night shift with only one can of energy drink, but now you need two to feel the same effects. That’s caffeine tolerance at work. 

Your body gets used to the amount of caffeine you regularly consume and will start needing more and more of it. And this can happen quickly — some researchers say you can develop a caffeine tolerance within three to five days of regular use. 

3. You’re Experiencing Withdrawal Symptoms  

You may also be experiencing caffeine withdrawal symptoms — fatigue is a big one — if you’re used to consuming large quantities of caffeine. One study found withdrawal symptoms get worse the higher the caffeine intake you’re used to. 

And you don’t even need to cut out caffeine altogether to feel this. If you’re used to consuming a large amount of caffeine through one brand of energy drink, and then switch to a different brand that contains less caffeine, your body may experience withdrawal symptoms. A different experiment in the same study found consuming 100 mg of caffeine less than you’re used to can cause withdrawal symptoms.

Symptoms of caffeine withdrawal include: 

  • Fatigue 
  • Headaches 
  • Depressed mood 
  • Difficulty concentrating 
  • Brain fog 

We’ve covered how long caffeine withdrawal symptoms last here, as well as how to overcome them. 

4. You’re Experiencing a Sugar Crash

It’s not just the caffeine crash that can make you feel sleepy — after the initial sugar rush comes the sugar crash. Your blood sugar levels will spike shortly after drinking a high-sugar energy drink, but the boost in energy will only last 30 to 60 minutes. After this, your blood sugar — and energy levels — will crash, leaving you feeling more tired than before. 

Symptoms of a sugar crash include: 

  • Tiredness
  • Headaches
  • Irritability
  • Difficulty concentrating 
  • Hunger — especially for more sugar 

5. Energy Drinks are Causing Sleep Loss 

RISE app showing how much sleep debt you have
The RISE app can tell you how much sleep debt you have.

Energy drinks can easily disturb your sleep, even if a cup of coffee doesn’t, due to their higher caffeine content. One study found students who reported a high caffeine intake were 1.9 times more likely to have difficulty sleeping and were 1.8 times more likely to be tired in the morning than students who said they had very low caffeine intake. The students mainly drank caffeinated soft drinks and coffee, but the point still stands — higher caffeine consumption impacts your sleep and next-day energy levels. 

Caffeine has a half-life of two to twelve hours. So, depending on how long your half-life is, if you knock back an energy drink to get you through the afternoon slump at work, you can still be feeling caffeine’s effects come bedtime. 

As caffeine stops adenosine from doing its job, it can easily make you not feel sleepy at bedtime, meaning you stay up later, and don’t get the sleep you need. The next day, your energy levels take a hit and you’ll most likely find yourself reaching for another energy drink — or anything else containing caffeine. This is how the vicious cycle of caffeine and sleep loss starts. 

And it gets worse each day as you build up sleep debt. Sleep debt is the measure of how much sleep you owe your body over the last 14 nights. It’s compared to your sleep need, which is the genetically determined amount of sleep you need each night. 

You don’t need to work these things out for yourself, though. The RISE app uses your phone use behavior and along with proprietary sleep-science-based models to calculate your sleep need and give you a number to aim for each night. The app also works out if you’re carrying sleep debt. 

The more sleep debt you build up when energy drinks disturb your sleep, the worse you’ll feel each day. 

Another sleep term you should be aware of? Your Melatonin Window. In the RISE app, this is what we call the roughly one-hour window of time when your brain will be producing the most melatonin it will all night. As melatonin is the hormone that makes you feel drowsy, it’s best to go to sleep during this one hour window, as you’ll find it much easier to fall and stay asleep. Even when the effects of caffeine wear off, you may not feel sleepy as you’ve missed this window of time altogether, meaning you’ll have a much harder time falling asleep.

How Can I Stop Energy Drinks From Making Me Feel Tired?

Now you know why energy drinks make you feel tired, it’s time to stop that from happening. Here’s what you can do:

Switch to Sugar-Free Energy Drinks (or Other Forms of Caffeine) 

If it’s the sugar crash that’s making you feel drowsy after drinking an energy drink, there’s an easy fix for that. Switch out your go-to drink for a sugar-free brand, or swap energy drinks for another sugar-free caffeinated drink altogether. This could include coffee, tea, or sugar-free soft drinks. 

The jury’s still out on the long-term safety of energy drinks, so switching to something like coffee or tea for your caffeine fix may also be better for your overall health. Experts recommend keeping consumption to one can of energy drink per day.  

Find Out (and Honor) Your Caffeine Cutoff Time 

RISE app screenshot showing what time to limit your caffeine
The RISE app can tell you when to stop consuming caffeine each day.

If caffeine is keeping you up at night, you may think you have to remove it from your diet altogether. But there is another way. By finding out your caffeine cutoff time, you may be able to enjoy caffeine — and all the energy-boosting benefits — and still fall asleep easily at night. 

Your caffeine cutoff time is the time of day you should stop drinking energy drinks — and consuming caffeine from other sources — to give your body enough time to metabolize it all by bedtime. 

This time will be different for everyone as it all depends on your circadian rhythm — or the roughly 24-hour body clock that dictates your energy levels. So while it may be around noon for some people, others — like night owls — may have a caffeine cutoff time around 2 p.m. 

RISE helps you figure out when exactly you should have your last energy drink of the day. The app predicts your circadian rhythm based on things like your phone use behavior and inferred light exposure, and then 10 hours before your Melatonin Window each night, you’ll be reminded to stop consuming caffeine. 

It’s not just energy drinks, though. Watch out for other caffeine-containing foods and drinks like coffee, black and green tea, soft drinks, and chocolate. Even decaf coffee contains caffeine, just in smaller amounts. 

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Reach for Natural Energy Boosts 

If you’re staying away from energy drinks in the afternoon in an effort to fall asleep faster at night or fall asleep at an earlier time, you can reach for these caffeine and sugar-free pick-me-ups instead. 

  • Get some exercise: Bonus points if it’s outside as the natural light will wake you up even more. 
  • Take a nap: 10-minute power naps can lower fatigue and increase cognitive performance, as well as help you pay down sleep debt. Just don’t nap too close to bedtime as you may find it hard to fall asleep later.
  • Take a cold shower: The cold water will increase your heart rate, blood pressure, and metabolism for a jolt of energy. Not close to a shower? Try splashing your face with cold water instead. 

We’ve covered other ways to wake yourself up here. 

Stop Energy Drinks Ruining Your Energy Levels  

There are a few reasons energy drinks can tank your energy levels — caffeine tolerance and withdrawal, sugar crashes, and sleep loss being the main culprits. All of these, however, can be fixed. 

The RISE app can tell you when your unique caffeine cutoff time is, so you know when to stop consuming it to stop it disrupting your sleep. Plus, RISE can help you pay down sleep debt, which will improve your energy levels long term. This way, you won’t need to rely on energy drinks to get you through the day, as you’ll be harnessing your own natural energy instead. 

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