Can Coffee Make You Sleepy? (Simply Explained!)

Suppose you’re a college student who has an exam the upcoming day, but it’s midnight, and you haven’t finished studying yet, so you drink a cup of coffee.  But, can coffee make you sleepy?

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“Maybe I should make another cup?” you tell yourself as you start to feel more tired. So you drink another cup but still end up dozing off. Sounds familiar?

I’ve certainly experienced this before, and let me tell you that, yes, coffee can make you sleepy. Here are the conditions that’ll counteract the usual effect of coffee:

  • Developing caffeine tolerance
  • Getting dehydrated
  • Adding too much sugar

If you want a more detailed explanation as to why coffee can make you sleepy, keep reading!

Why Coffee Makes You Sleepy

You’re probably curious about why coffee can make you sleepy, so I’ve compiled a list of the most common reasons.

You Add Too Much Sugar to Coffee

Do you like to add lots of whipped cream or sugar to your coffee? Believe it or not, the extra dose of sweetness might be the culprit to your sleepiness after drinking coffee.

Consuming too much sugar at once leads to what people call a sugar crash. To lower glucose levels in your blood after drinking coffee, your body secretes large amounts of insulin, which returns your glucose levels back to normal.

Since blood glucose gives you energy, the sudden drop caused by insulin will counteract this effect, making you feel tired and sleepy. Other common symptoms of a sugar crash include dizziness and mood swings.

You can prevent this from happening by limiting your sugar consumption.

You’re Dehydrated

Coffee is a diuretic, which means it makes you urinate often. This won’t be noticeable if you drink a cup of coffee or two a day. But you’ll definitely experience that if you drink more than three cups daily. 

So, is this related to feeling sleepy? The answer is simple: when you urinate a lot from drinking too much coffee, you lose fluids from your body, which leads to dehydration. 

And surprisingly, dehydration can trigger sleepiness and fatigue, according to research

Other symptoms of dehydration include:

  • Dry mouth and tongue
  • Lack of sweat
  • Dizziness
  • Dark yellow pee

Luckily, that’s an easy problem to fix. Whenever you feel dehydrated, eat fruits and vegetables rich in water, such as cucumbers and watermelons, and increase your water intake if you live in a cold, humid area. 

Kindly note that you should consult a doctor if you experience confusion or a high breathing rate because it might mean you’re extremely dehydrated.

You Developed Caffeine Tolerance

If you’re a regular caffeine consumer like me, there’s a chance your body developed a tolerance to it. Caffeine has a chemical that blocks adenosine receptors, which are responsible for inhibiting your brain activity and making you sleepy. This is how it keeps you alert.

When these receptors are blocked, your body creates more of them to compensate. Now, if your body is more tolerant to caffeine than before, it’ll wear off quicker than normal, so the old adenosine receptors will be unblocked. This leads to an adenosine buildup in your body, which can make you feel sleepier than usual.

You can reset your caffeine tolerance by gradually cutting down the number of coffee cups you drink daily. 

Your Coffee Has Mold 

I know it sounds gross, but you might be feeling sleepy because there’s mold in your coffee. There are certain types of coffee beans, such as green coffee, that commonly contain mycotoxin, which is a micro fungus that causes chronic fatigue. It also causes dizziness and sleepiness.

Mycotoxin is more likely to grow in improper packaging and storage conditions. So before buying coffee, make sure you’re purchasing from a high-quality and trustworthy brand.

You’re Stressed

If you’ve been feeling stressed recently, drinking caffeine might make it worse. There’s a 2017 study that concluded people who consume caffeine double their cortisol and adrenaline levels, which are stress hormones.

When you feel stressed, your body activates a fight-or-flight response that renders it ready for any nearby danger. But of course, the danger is only in your mind, so your body will stay alert for no reason. After the fight-or-flight hormones wear off, the surge of energy you have will go along with them, leaving you all sleepy and tired.

You can counteract high-stress levels by giving your body time to rest and limiting your caffeine intake for a while.

You’re Sleep-Deprived

If you haven’t been getting enough sleep lately, your body will eventually catch up and make you feel tired and sleepy. More so, if you’ve been sleeping for less than six hours in the past two weeks and drinking coffee to stay up longer, you’ll make matters worse. 

This is because you can’t avoid fatigue with coffee. And sure, it might temporarily make you feel alert, but the exhaustion will eventually add up. So, try to avoid staying up for too long and exhausting your body.

You Add Dairy to Coffee

If you like to add milk to your coffee, this might be why you feel sleepy. Dairy products contain a chemical substance called tryptophan that can help you sleep faster.

If you feel like this might be the reason, try drinking your coffee without milk and keeping an eye out for any difference.

You Have Withdrawal Symptoms

This might be surprising to you, but you can experience withdrawal symptoms even if you didn’t eliminate coffee from your diet. One notable study reports that people who cut out a single cup of coffee started to experience withdrawal symptoms. 

In other words, you might feel sleepy if you start to drink two cups of coffee instead of three. You’ll often notice withdrawal symptoms 12 hours after drinking your favorite beverage.

Here are signs that indicate you’re experiencing caffeine withdrawal:

  • Headache
  • Irritability
  • Fatigue
  • Confusion
  • Depressed mood
  • Nausea
  • Muscle pain

How to Prevent Coffee From Making You Sleepy

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After knowing why coffee makes you sleepy, you probably want to know how to prevent that. So, here are a couple of suggestions.

Get Rest

If you’re sleep-deprived, the only way to prevent coffee from making you sleepy is to get rest. And even if you can’t sleep enough at night, you can take power naps throughout the day and have a relaxing environment at bedtime to improve sleep quality

Restrict Coffee Intake

Consuming too much caffeine might be the cause of struggling with sleepiness throughout the day. In this case, you need to put restrictions on the number of coffee cups that you drink. And don’t forget to restrict any other beverages that contain caffeine, too, like energy drinks and tea.

Ideally, you shouldn’t drink coffee in the afternoon to sleep better at night. This way, you’ll no longer feel sleepy during the day.

Sync With Your Circadian Rhythm

The circadian rhythm, which is the internal body clock that regulates the sleep-wake cycle, can tell you when to rest or get active. And even though you can’t change your energy levels during the day, you can stay in sync with the clock by doing demanding tasks when you’re energetic and taking a nap when you’re sleepy.

Reduce Your Sugar Intake

Since sugar can spike your blood sugar levels and cause a dip in energy, you should cut back on it. This is especially true if you have diabetes because your body can’t regulate insulin levels in the blood. You should keep in mind that sweeteners like whipped cream, syrup, etc., count as sugar too. 

Other Side Effects of Coffee

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You might experience side effects if you drink coffee excessively (> 4 cups). Here are some of them.

Digestive Issues

Coffee has laxative properties that cause your body to release gastrin, which aids in digestion. There’s also a study that shows decaf coffee has the same properties. 

But here’s the catch. Caffeine can get your bowels moving by increasing peristalsis, which are the contractions that move ingested food through the GIT. This means that drinking caffeine can cause diarrhea and loose stool when consumed in excess. 

Also, some studies show caffeine might worsen GERD symptoms. The reason could be that caffeine relaxes the esophageal sphincter that prevents food from going up to the mouth, leading to acid reflux. 

If you’re experiencing GERD symptoms, you should reduce your daily caffeine intake.

Caffeine Addiction

Caffeine can turn into an addiction for some people because it causes chemical changes in the brain. And when you drink the same amount of coffee daily, you develop tolerance to it. This might make you feel the need to drink more cups of coffee to get the same effect. 

This has been shown in a study that asked participants to report any side effects after not drinking coffee for 16 hours. The participants said they noticed withdrawal symptoms such as headaches, difficulty concentrating, and irritability. 

While it might differ from one person to another, if you drink more than 400 mg of caffeine daily, you’re most likely addicted to it.


Coffee is an ideal drink to enhance alertness. This is because caffeine can increase the release of adrenaline, which raises your energy levels. But drinking too much can heighten this effect and lead to irritability and anxiety. 

So, how much caffeine is too much? 1,000 to 1,500 mg of caffeine will certainly induce anxiety, so you shouldn’t consume this much in a day. Also, people who are sensitive to caffeine are more likely to experience these symptoms with low-to-moderate doses, so it can vary depending on your tolerance. 

But as a general rule of thumb, you should drink coffee moderately. And if you start to experience nervousness throughout the day, you should reduce your intake.

Fast Heartbeat

Since caffeine is a stimulating substance, it can increase your heart rate as a side effect. And if the caffeine intake is too high, it might lead to atrial fibrillation, which means an irregular heartbeat rhythm. 

However, there’s also a study that reports 51 people who have heart failure could consume one cup of coffee an hour for a total of five hours without any abnormal changes in their heart rate. 

These mixed studies indicate that a fast heartbeat doesn’t take effect for everyone. But regardless, always consume coffee moderately. 


When Does My Body Get Rid of Caffeine?

Caffeine can stay in your body for 10 hours. You’ll start slightly noticing the effects within 15 minutes, but they’ll reach their peak after an hour or two. Then, your body will metabolize half the amount of caffeine after 6 hours and will fully get rid of it after 10 hours.

Is Coffee Harmful?

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No, coffee isn’t harmful. In fact, it has health benefits like lowering the risk of type 2 diabetes. However, it can have side effects such as restlessness and muscle tremors if you consume it in excess. According to FDA, you can safely drink up to four cups of coffee daily. 

Why Doesn’t Coffee Affect Me?

There are many reasons coffee doesn’t make you awake. Maybe you didn’t drink enough, or you take medications that delay caffeine’s effects, such as antidepressants and hypertension medications. 

Another possible reason is that you genetically have adenosine receptors that don’t bind strongly to caffeine, so your favorite drink can’t prevent you from feeling sleepy.

When Do Caffeine Withdrawal Symptoms Stop?

Many factors can contribute to the length of caffeine withdrawal symptoms, such as the amount of caffeine consumed and genetics. 

But you’ll start to notice the symptoms 12 to 24 hours after drinking coffee, and they’ll go away after two to ten days. Also, some symptoms can last for up to three weeks, such as headaches.

When Should You Stop Drinking Coffee?

You should cut out coffee if it starts to negatively affect your mood. For example, if you find yourself stuck in an endless cycle of staying up late and then struggling to sleep at night, it’s best to change your coffee-drinking habits.

Can Decaf Coffee Make You Sleepy?

No, there’s no research that says decaffeinated coffee can make you sleepy. However, if you’re sensitive to caffeine, drinking decaf coffee might make you struggle to sleep. This is because it still has 3% of the caffeine in regular coffee.


By now, you should know that coffee can make you sleep, but only under certain conditions. For example, consuming too much caffeine might make you dehydrated, so your body will lose fluid, and you’ll feel tired and sleepy.

Another scenario is that you consume too much sugar in your coffee, so your body experiences sugar crashes, which lead to fatigue and sleepiness.

Overall, you can prevent caffeine from making you sleepy by drinking it moderately, getting enough rest, and restricting your sugar consumption.

Penny Albright
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