The Betterment Project

Why Caffeine Can Sometimes Make You Feel Tired

Many of us wake up and walk straight over to our coffee machines in the morning. We take breaks with caffeine. We do lunch with caffeine. Caffeine is there with us when we’re fighting sleep, trying to meet a deadline, or just wanting a slight boost in our energy levels throughout the day. 

People profess their love for caffeine, like coffee and soda on social media, on t-shirts, on coffee cups, and in the quiet moments in the early morning hours when they feel their morning beverage start to wake them up. 

Caffeine in all its glory has become such a prevalent part of our society that it even helps define us. As Joe Fox (Tom Hanks) in You’ve Got Mail explains: “The whole purpose of places like Starbucks is for people with no decision-making ability whatsoever to make six decisions just to buy one cup of coffee. Short, tall, light, dark, caf, decaf, low-fat, non-fat, etc. So people who don't know what the hell they're doing or who on earth they are can, for only $2.95, get not just a cup of coffee but an absolutely defining sense of self: Tall. Decaf. Cappuccino.” Some people are Team Coffee, Team Tea, Team Soda, or Team Energy Drink, but the common thread is a fondness for caffeine.

The question is, what do we know about caffeine? What is caffeine? What is it about caffeine that we love so much? In truth, sometimes caffeine doesn’t do what we want, so why do we feel tired after caffeine sometimes? What can we do about it?

Caffeine: What Is It?

It might be an unpopular fact to say out loud, but caffeine is a drug. Caffeine is from the
methylxanthine drug class, and it’s a substance that occurs naturally in over 60 plants. 

Some well-known places to find caffeine in nature are:

  • Coffee beans
  • Tea leaves
  • Kola nuts 
  • Cacao pods

While caffeine is considered a drug, it is widely available, and it is used worldwide. In North America, more than 80 percent of the adult population reports consuming caffeine regularly. Most people get their caffeine from drinks like coffee, tea, or soda. 

Caffeine is a stimulant. That means that caffeine increases your brain activity and the activity in your nervous system. It also works to improve the circulation of chemicals like cortisol and adrenaline in the body. 

Caffeine’s effect on the brain is considered a psychoactive substance, but that doesn’t decrease its popularity. So, why do we love caffeine so much?

Why Do We Love Caffeine?

According to Dr. Solomon Snyder, people love caffeine because it
elevates our moods, decreases our fatigue, and enables us to work harder and think more clearly. Caffeine is how many of us greet each day, and that may be due to caffeine’s ability to help put our body’s daily clock in motion. 

Caffeine affects our body’s metabolism. Some of the effects are:

  • Stimulation of the central nervous system - Hello, boost of energy!
  • Stimulates the ridding of salt and water from the body through increased urination because it is a diuretic
  • Stimulates the release of acid in the stomach
  • Increases blood pressure

Caffeine’s effects are at their peak within 40 to 60 minutes of consumption. Caffeine and its effects can also stick with you for four to six hours afterward. 

Caffeine Consumption


Caffeine is not only found in beverages and chocolate. It is sometimes used in other medicinal applications in the treatment of things like:

  • Asthma
  • Migraine headaches
  • Gallbladder issues
  • Attention deficit-hyperactivity disorder (ADHD)
  • Athletic performance enhancement

Most of these applications lack the scientific evidence to fully support the use, but it is still a common substance used. As with any other drug, there are limits to how much a person can and should take. The FDA recommends limiting consumption to 400 milligrams per day for the average adult. That’s about four or five cups of coffee. However, everyone’s tolerance can be different. 

Because caffeine is widely available and left to you to self-regulate, it’s entirely possible to overindulge. As they say, too much of a good thing turns bad, so here are some signs that you’ve consumed too much caffeine:

  • Restlessness
  • Shakiness
  • Insomnia
  • Dizziness
  • Headache
  • Rapid heartbeat
  • Dehydration
  • Increased feelings of anxiousness

Like other substances, it is possible to develop a dependency. But, why does it make us feel tired instead sometimes?

Why Does Caffeine Make Us Feel Tired  Sometimes?

When you down an afternoon coffee, you expect to feel a wave of energy to help you power through, so it’s a bit of a shock when you’re struggling to hold your eyes open within the hour. So, what gives?

1 - Blocked Adenosine Effects

When consumed, the stomach absorbs caffeine and small intestines, usually through a beverage, and caffeine is then redistributed into the bloodstream. As it makes its way through your body, caffeine also makes its way to the brain. Caffeine adheres to the brain’s adenosine receptors. 

Adenosine helps communicate sleepiness to your body and helps control your sleep-wake cycle. Caffeine keeps your brain from processing your adenosine, but you’ll still produce it. When the caffeine wears off, and your brain begins to receive the messages again, the adenosine will convincingly make you feel tired.

2 - Diuretic Effects

When you’re happily consuming caffeine, you can lose track of just how much caffeine has entered your body. However, your body will notice and begin to feel the diuretic effects. As you frequent the restroom more, you may lose more fluids than you’re consuming. The resulting dehydration may be to blame for why you feel tired.  

Other signs to look for that your caffeine consumption could be causing dehydration are:

  • Dry mouth
  • Thirst
  • Dry skin
  • Dizziness
  • Not sweating

There is water in your beverage, so it may not be causing dehydration alone. However, other factors can exacerbate the situation and require you to be more attentive to your overall water consumption. If you’re sick, exercising more frequently, or experiencing hot, humid, or cold climates, you may want to consume more water than usual. 

3 - Stress Effects

When you’re
stressed, you may experience sleep disruptions. Many of us turn to caffeine as a constant companion in times of stress. When we have a deadline to meet, caffeine can help us, but when you combine the wakefulness that comes with stress and the effects of caffeine, sleep can be an elusive creature

Calming our minds can help us reduce our stress levels. Reducing stress can also help lower our cortisol levels which caffeine also helped to elevate. Too much cortisol can fatigue you, so reducing stress and reducing your caffeine consumption can help regulate your levels. 

4 - Lack of Sleep

Caffeine can cause you to struggle when it’s time to sleep. If we consume caffeine too late in the day, it can be challenging to fall asleep. It’s possible that when you feel tired after consuming caffeine, it’s not that the caffeine isn’t working. It could be that the caffeine can’t bring you out of the state of tiredness you are in from the lack of sleep the night before.

Caffeine does a lot to keep you awake. As listed above, it blocks adenosine reception and increases cortisol levels, which can keep you awake at night. In addition, caffeine causes an increase in epinephrine in the body. Epinephrine is also known as adrenaline. It takes quite a while to settle down for sleep when your adrenaline is pumping. 

To counter these effects, it may be necessary to prioritize your sleep. Adjusting your caffeine consumption to allow you time to still fall asleep at night can do wonders for helping you not to feel tired after a cup of caffeine when you do consume it. 

5 - Mistaken Identity

While it’s possible for caffeine to be causing you to feel tired, it could be there’s something else at fault. Many of us consume caffeine, and most forms of caffeine consumption contain sugar. We sweeten our coffee, tea, energy drinks, and more with sugar. So, it’s possible that the tired feeling you get is the result of a sugar crash. 

When you introduce the sugar, your body begins to produce insulin to counter it. The insulin causes your blood glucose or blood sugar levels to drop. Your body receives energy from your blood sugar as a leading supplier of energy. When the levels begin to drop, you will feel tired. So, maybe caffeine is getting a bad reputation without reason. 

You may add insult to injury if you’re consuming a sugary or carbohydrate-loaded snack on the side, so consider adding protein to help stabilize your blood sugar levels and avoid the crash.

Keep Calm and Sleep More With ASYSTEM

If you’re having trouble falling asleep, ASYSTEM’S
Complete Calm Sleep Gummies can help support your overall sleep health. Sleep tends to affect our mood, stress, and productivity. That’s why we created a solution.

Here are some tips to get started and aspects to look forward to after taking a sleep gummy:

  • We recommend taking one gummy 30-60 minutes before bedtime.
  • They come in a delicious wild berry flavor.
  • You’ll feel a calming sensation, all thanks to our unique Terpene blend.
  • The following day, you’ll wake up feeling refreshed and ready to take on the day.
  • After using the sleep gummies for an extended period of time, your overall sleep health will improve. 



Caffeine is one of nature’s gifts to a tired mind and body. However, like us, caffeine is fallible. It doesn’t always make us feel awake. Sometimes it makes us feel tired. When caffeine isn’t working its usual magic, it’s time to look at our consumption levels. Are you using it to excess? Are you expecting miracles when you need sleep? 

Caffeine does a lot for us, but as we self-regulate this common drug in our lives, it’s important to remember that it has a time and place and limits. Remember to monitor yourself, stay hydrated, and rest your body. Caffeine will still be there when you wake up.


Methylxanthines in asthma | 

Kola nut: so much more than just a nut | 

Spilling the Beans: How Much Caffeine is Too Much? |

Drugs (psychoactive) | WHO 

The Secrets of Caffeine, America's Favorite Drug | NY Times 

What is Caffeine? - Everything Caffeine | Food Insight 


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This article has been reviewed by members of our Scientific Advisory Board.

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