Why Does Coffee Make Me Sleepy? 4 Reasons to Understand

By Shabbir
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When we think of coffee, we think of a perk up drink that gets you fresh and out of bed, ready to take on the world for a new day. Many of us just can’t function before some warm coffee goodness goes into our bellies. However, some of us are not quite as fortunate and may end up more tired after a cup.

So that begs the question: why does coffee make me sleepy?

The reality is that it’s not the coffee itself that makes you sleepy, but there are other factors around it that can cause you to feel tired and sleepy. Things like caffeine wearing off, dehydration, and sugar can make you feel tired. Because it happens shortly after a drink of coffee, we tend to conflate it with coffee instead of the real reason!

This post is a bit of a science lesson, so feel free to check out the sources we’ve linked out to for more information.

coffee making you sleepy

Why does coffee make me sleepy instead of awake

The caffeine begins to wear off

Coffee contains many compounds, but it’s best known for caffeine. So how does caffeine last?

When you drink coffee, the caffeine is absorbed by your stomach and small intestine, enters your bloodstream, and begins to flow around your body.

Your brain produces a chemical called adenosine, which signals the body to wind down and begin to sleep. When caffeine reaches your brain, it binds to the receptors that receive the adenosine signals, preventing you from feeling tired right away.

What’s important to note is that your brain does not stop producing adenosine. It’s just that the adenosine receptors are not able to bind to the adenosine to receive the signal. [1]

So now, what happens is that your body is producing adenosine as it would, and there’s a lot more of it now than there would be otherwise.

Once the caffeine wears off and the adenosine receptors are free again, there’s more adenosine to bind to them and send the signal to your body to sleep and wind down.

The result: you feel sleepy!

In reality, if you’re already really tired, coffee will not make the tiredness disappear. Your body needs sleep to function, so while coffee may be able to stave off sleep for a little while, you’ll still end up feeling tired.

Your coffee is very sugary

Another culprit for when you drink coffee but you’re still tired is sugar. Most drinks on a coffee shop menu are notoriously sugary.

When you consume a large amount of sugar, your body produces a lot of insulin to break the sugar down. If there’s too much sugar, your body produces too much insulin as a response, and all that insulin ends up breaking down so much sugar that your levels drop and you start feeling hungry and lethargic.

If you have your coffee with a lot of sugar, try opting for black coffee instead, or try to sweeten your coffee with maple syrup or honey rather than sugar.

Also, ditch the creamer, as it’s full of sugar.

You can learn more about how this works in this really informative video:

Your coffee is moldy (yes, you read that right)

Did you know that most cheap coffee is full of mold spores? Most supermarket coffee is low-grade stuff from South American and South-east Asian countries.

These bulk farms tend to process coffee in less than optimal ways, and that results in the coffee cherries fermenting and growing mold.

Mold results in mycotoxins in your coffee, and when you are exposed to mycotoxins, you can end up feeling drowsy or have brain fog [2].

When coffee is properly washed and processed, mold is rarely an issue, so as long as you’re buying the good stuff, you should not run into this issue.

Avoid buying coffee from the supermarket and instead check out smaller roasters. Lifeboost coffee happens to pride themselves in selling mold-free coffee, and their coffee happens to be delicious, so they’re definitely worth giving a shot.

Coffee is a diuretic

Coffee is a notorious diuretic. Just like beer and other alcoholic drinks, coffee makes you need to go to the bathroom. While one cup of coffee does not contain enough caffeine to offset the amount of water you’re actually drinking through the coffee, enough coffee can make you lose more water than you retain.

As you know, dehydration is bad. Dehydration can cause fatigue, dizziness, and confusion. If this is the case and you drink another cup of coffee, the situation can become worse!

A sign of dehydration is dark, concentrated, and foul-smelling urine [3].

Fortunately, routine dehydration is really easy to counter – just drink some more water and less coffee 🙂

What if coffee makes me tired but energy drinks don’t?

The jury is still out on why some people only feel tired after a drink of coffee but not after chugging an energy drink. One possible explanation is that energy drinks like Red Bull actually contain less caffeine than a cup of coffee of the same size [4], so the caffeine crash is lighter.

Also, energy drinks contain a lot more ingredients than black coffee, and it’s possible that those are playing a role in this.

Why does coffee make me sleepy immediately?

Coffee can make you sleepy immediately if you have developed something called caffeine tolerance [5], which can happen if you have a habit of drinking multiple cups of coffee for a long period of time. In this case, you might drink a cup of coffee but the caffeine has a decreased effect on you thanks to the tolerance you have built up over time.



It’s tempting to think that the coffee itself is making you feel tired, but the truth is that the factors around coffee are what actually cause your drowsiness and tiredness. The best way to avoid feeling tired is to get a good night’s sleep! This probably sounds like the most obvious thing in the world, but it’s true!

Caffeine can heighten your senses for a short time even if you’re sleepy, but as soon as it begins to wear off, your body’s natural sleep mechanism will kick in and try to force you to sleep!


  1. https://pubmed.ncbi.nlm.nih.gov/10344585/
  2. https://www.suzannegazdamd.com/blog/mold-mycotoxin-and-what-it-means-for-your-brain-health
  3. https://www.mayoclinic.org/diseases-conditions/dehydration/symptoms-causes/syc-20354086
  4. https://www.caffeineinformer.com/caffeine-content/red-bull
  5. https://www.healthline.com/nutrition/caffeine-tolerance
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About Shabbir

Shab is the Chief Caffeine Officer at Coffee Brewster. When he's not weighing out coffee beans for his next brew, you can find him writing about his passion: coffee.