Why does coffee make me sleepy instead of awake?

In this article, we will answer the question, “Why does coffee make me sleepy instead of awake?”. In addition, we will discuss the relationship of caffeine with sleep, how this relationship is given according to the amount of caffeine consumed,  if the effects of caffeine are the same for everyone and what are the pros and cons of drinking coffee for your sleep.

Why does coffee make me sleepy instead of awake?

Coffee makes you sleepy because it contains caffeine, a molecule that blocks the effect of adenosine, which signals our brain that we are tired. However, this is only temporary, as the caffeine is essentially tricking your brain. 

When the effects of caffeine wear off, you may feel even sleepier than before you had the coffee.

In addition, the more caffeine you consume, the more caffeine you need to stay awake. This is because the adenosine receptors in your brain increase in number, demanding more and more caffeine to keep you alert. (1).

What is the relationship of caffeine with sleep?

The relationship of caffeine with sleep is it interferes with the way our body perceives that it is tired.

As you use energy during the day, you use ATP (adenosine triphosphate), commonly called the “energy currency” of cells. ATP stores and supplies energy to the body. As you expend energy throughout the day and ATP is broken down, adenosine is released as a byproduct. 

Adenosine accumulates in your bloodstream and brain. By the end of the day, the amount of adenosine reaches a peak, which sends the signal of low energy to your brain and the information that you are tired to your whole body. 

This occurs because adenosine binds to its receptors in the brain, sending signals of tiredness and sleepiness throughout the body.

Since caffeine and adenosine have similar chemical structures, caffeine molecules can bind to the adenosine receptor site, with posterior degradation, while adenosine accumulates in the brain.

The body recognizes when adenosine accumulates and sends signals to the brain to create more receptors. This means the more caffeine you consume, the more you’ll need to avoid feeling tired. If you still feel tired and unwell after drinking coffee, you likely have a caffeine tolerance.

In addition, continuous caffeine consumption leads to the buildup of adenosine in the brain. As a result, several hours after ingesting caffeine and as the body metabolizes it, all the available adenosine in the brain binds to the receptors. This can leave you feeling exhausted once the effects of the coffee wear off (2).   

How do different amounts of caffeine affect our sleep?

Different amounts of caffeine can affect our sleep in various ways. For instance, small amounts of caffeine, such as those found in green tea, can promote relaxation and unwinding.

Moderate doses of caffeine (50-300 mg) can enhance alertness, energy, and concentration. However, larger amounts can lead to adverse effects such as anxiety, restlessness, insomnia, and an increased heart rate.

The amount of caffeine you consume can also impact how your body metabolizes it. For example, as you drink more coffee, your liver produces more proteins that metabolize caffeine, which can modify its effects on your body.

Furthermore, the more caffeine you consume, the more caffeine your body will require to maintain the same levels of alertness and concentration as before. 

Once all the adenosine receptors are occupied, adenosine builds up in the brain. Therefore, when the effects of caffeine wear off, the “rebound effect” occurs, causing your body to feel even more tired than before consuming coffee.

Lastly, monitoring your total caffeine intake throughout the day is crucial. It is recommended not to exceed 400 mg of caffeine per day, to avoid excessive caffeine’s adverse side effects (3-5).

Are the effects of caffeine the same for everyone?

The effects of caffeine vary significantly from person to person. Among several factors, there are mainly behavioral and genetic issues.

The consumption of certain foods, beverages, medications, and drugs can interfere with caffeine metabolization.

The amount and frequency of coffee consumed also facilitate the development of a certain tolerance, reducing the effect of caffeine.

Smoking cigarettes speeds up the metabolism rate of caffeine, which explains why smokers drink a lot of coffee.

Among the genetic issues are mainly variations between individuals in the expression of caffeine-metabolizing enzymes, which can accelerate or decelerate its effects.

For example, in the liver, enzymes of the Cytochrome P450 family (CYPs) are among the main metabolizers of caffeine, and one of them that is very important for metabolizing caffeine, the CYP1A2 enzyme, can vary from person to person (1,6).

What are the pros and cons of drinking coffee for your sleep?

Coffee has the potential to offer some benefits, such as inducing relaxation and drowsiness, that may help some people fall asleep faster. 

In addition, some studies suggest that coffee consumption may be linked to a lower risk of certain sleep disorders, like sleep apnea and restless leg syndrome. 

However, coffee also has potential drawbacks. For instance, consuming coffee before bedtime can disrupt the natural sleep-wake cycle, making falling and staying asleep harder. 

Caffeine can reduce the amount and quality of deep, restorative sleep, leading to fatigue and impaired cognitive function during the day. Additionally, excessive coffee intake can cause other adverse health effects, such as increased heart rate, anxiety, and digestive problems.

It’s important to note that the effects of coffee can vary depending on factors such as the amount consumed, the time of consumption, and individual differences. Therefore, some of its effects remain controversial (1,6).


In this article, we answered the question, “Why does coffee make me sleepy instead of awake?” Furthermore, we discussed the relationship between caffeine and sleep, how this relationship is given according to the amount of caffeine consumed, if the effects of caffeine are the same for everyone and what are the pros and cons of drinking coffee for your sleep..


1. Gardiner C, Weakley J, Burke LM, Roach GD, Sargent C, Maniar N, et al. The effect of caffeine on subsequent sleep: A systematic review and meta-analysis. Sleep Med Rev. 2023 Jun 1;69:101764.

2. Reichert CF, Deboer T, Landolt HP. Adenosine, caffeine, and sleep–wake regulation: state of the science and perspectives. J Sleep Res. 2022;31(4):e13597.

3. O’Callaghan F, Muurlink O, Reid N. Effects of caffeine on sleep quality and daytime functioning. Risk Manag Healthc Policy. 2018 Dec 7;11:263–71.

4. Borrás S, Martínez-Solís I, Ríos JL. Medicinal Plants for Insomnia Related to Anxiety: An Updated Review. Planta Med. 2021.

5. Eskelinen MH, Kivipelto M. Caffeine as a protective factor in dementia and Alzheimer’s disease. J Alzheimers Dis. 2010;20 Suppl 1:S167-174. 

6. Parry D, Iqbal S, Harrap I, Oeppen RS, Brennan P. Caffeine: benefits and drawbacks for technical performance. Br J Oral Maxillofac Surg. 2023 Apr 1;61(3):198–201.

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