Why Doesn’t Caffeine Affect Me?

Coffee Geek Lab / Why Doesn’t Caffeine Affect Me?
Yurii Brown

Certified Barista

March 30, 2021

Coffee consumption in the United States has exceeded 27 million 60-kg bags in the 2018-19 fiscal year. That’s 1.5 million more compared to the 2017-18 fiscal year (1).

Americans are truly a nation of coffee lovers, and yet, some of us still get completely unaffected by the main component of this vigorous potion, which is caffeine. You probably have that one friend who literally bathes themselves in Americano and then just goes to sleep. Or, you can be that friend.

So, why caffeine doesn’t affect you?

Well, let’s see!

There are a lot of factors that can impact your sensitivity to caffeine, and we will break down each of them in this article!

What is Caffeine and How Does It Work?

What is Caffeine and How Does It Work?

Source: https://coffeecorner.com/caffeine/

Caffeine is an alkaloid compound that naturally occurs in plants like coffee, cola, tea, and cocoa. Pure caffeine has a form of white small, salt-like crystals and a very bitter taste. It’s soluble in water and can be toxic in high amounts.

When you drink coffee, caffeine binds with adenosine receptors in your brain. Adenosine is one of our inhibitory neurotransmitters. Its production begins right after you wake up and helps to induce sleepiness in the evening hours. By binding with adenosine receptors, caffeine prevents them from triggering the sleepy state and keeps you alert. 

Chocolate, cola beverages, and tea have smaller amounts of caffeine, so effects are less prominent. On the other hand, caffeine in energy drinks is often paired with sugar and can trigger a rapid energy boost with a quick decline, which can be sufficient for improving mental performance.

Main Reasons Why Caffeine Doesn’t Affect You

Now that you know about how caffeine works, let’s investigate what can alter this pattern and prevent you from experiencing its effects. 

#1 Tolerance Levels

Those who consume coffee daily and in large quantities can develop caffeine tolerance, which means that your response to the stimulating effects of caffeine can decrease over time.

That’s because your body starts to produce more adenosine in response to coffee consumption so that the adenosine molecules can have higher chances to bind with receptors (2). So you might start to feel like you need more coffee to feel alert.

Also, caffeine stimulates your body to produce energy by using glycogen stored in the muscles and liver. If you don’t have enough glycogen in these deposits — for example, if you’re on a low-carb diet — then there’s no energy fuel to use, and the effects of caffeine might feel less potent for you.

#2 Sex and Genetics

Another reason why caffeine doesn’t work for you might be your sex. Studies show that men start to experience the effects of caffeine more quickly than women — in 10 minutes after they make their first sip (3). 

If you’re a woman, you might have to wait for 5-10 minutes more to experience the effects of your morning cup, and these effects won’t be as prominent as in men.

Genetics is another factor that can impact your initial caffeine sensitivity. Caffeine metabolism is regulated by two factors: cytochrome CYP1A2 which produces an enzyme that metabolizes caffeine from your bloodstream, and the AHR gene that controls the amount of enzyme you can produce (4). 

Simply speaking, these two factors can control how much caffeine can circulate in your bloodstream at a time and for how long. This can explain why some people can drink a double espresso shot and then fall asleep peacefully, and others drink a small cup of diluted Americano and will toss and turn all night.

#3 Health Conditions & Medications

Certain medications and health conditions may affect your caffeine sensitivity.

For example, during a depressive episode, you might have chemical balance in your brain shifted to the lack of stimulatory neurotransmitters. This means that you will generally have low energy levels and your standard cup of coffee might not help you to boost them.

Some medications, such as diuretics, antacids, or antibiotics, can also slow down your caffeine metabolism and make you crave more coffee to achieve the desired effects.

#4 You Drink Too Little (Or Too Much)

Our body is a really smart system, and it knows the exact quantities of different nutrients and chemicals it needs. 

Caffeine is no exception, and you may easily lose all its beneficial effects if you tweak your dose on both sides.

  • If you drink too little caffeine, your body simply won’t have sufficient caffeine levels in the system to bind with adenosine receptors and keep you alert.
  • If you drink too much caffeine, the adverse effects, such as irritability, headache, and high blood pressure, will take over much sooner than you’ll be able to feel positive effects. A high dose of caffeine is more than 400 mg per day, which is equal to 4 standard cups of filtered coffee.

#5 Poor Sleep Patterns

You already know about adenosine, the inhibitory neurotransmitter that helps us get sleepy in the evening. When we sleep, the adenosine production stops, and our body breaks it down and removes it from the system.

However, if your sleep schedule is inconsistent, or if you sleep less than 7 hours per night, you will have some residual adenosine in your brain upon awakening. This will reduce the chances of caffeine binding to adenosine receptors, and you might feel like caffeine doesn’t work for you and drink more.

#6 Dehydration

Dehydration effects of your morning Americano are one of the common coffee myths. You won’t be more dehydrated than you already are if you drink a cup of coffee.

However, if you don’t consume enough clear water and are constantly dehydrated, this may reduce the effects that caffeine has on your body

One of the symptoms of dehydration is the feeling of sleepiness and reduced mental performance. So, if you drink coffee to combat that, it might not work.

Drink a glass of water instead and see if that brightens your mind. If not, you might refer to a cup of Joe for a refreshment.

Finally, Different Brewing Methods Contain Different Amounts of Caffeine

Regular coffee without additives like milk and sugar doesn’t have calories, only a certain amount of caffeine. And this amount can drastically fluctuate between different coffee blends and brewing methods. Most coffee blends are composed of Arabica and Robusta beans in different proportions. Robusta beans typically have two times more caffeine than Arabica, and if you pick a Robusta-dominant blend, it will have a more invigorating effect on you. Also, there are A LOT of different coffee brewing methods, and you can try most of them at home. And here’s how the caffeine content per cup (8 oz.) varies from method to method:
  • Filter coffee — 145 mg per cup (can vary from 120 to 175 mg);
  • French press — 107 mg per cup (can vary from 85 to 135 mg);
  • Percolator — 200 mg per cup (can vary from 65 to 275 mg);
  • Turkish coffee — 200 mg per cup (can vary from 160 to 240 mg);
  • Cold Brew — 200 mg per 16 oz. bottle on average.
Bottom line? Don’t be afraid to experiment, and you will find a coffee brew that works best for you!


A lot of things can affect your caffeine sensitivity, from genetic factors to your sleep schedule. Some of them aren’t reversible, but that doesn’t mean you don’t have to enjoy your cup of coffee. You may just need to find your perfect blend or brewing method, and consume everything in moderation, so you won’t develop tolerance.

Are you sensitive to caffeine? How many cups of coffee per day do you drink? Share your answers below!

Additional Resources:

  1. M. Shahbandeh (2020, October 8). Coffee consumption in the U.S. 2013/14-2019/2020. Retrieved from https://www.statista.com/statistics/804271/domestic-coffee-consumption-in-the-us/ 
  2. H. P. Ammon (May 1991). Biochemical mechanism of caffeine tolerance. Retrieved from https://pubmed.ncbi.nlm.nih.gov/1888264/ 
  3. Ana Adan, Gemma Prat, Marco Fabbri, Miguel Sanchez-Turret. (2008, December 23). Caffeine Has Greater Effect On Men, And Starts Only Ten Minutes After Consumption. Retrieved from https://www.sciencedaily.com/releases/2008/12/081222113526.htm 
  4. Michelle Z. Donahue (2018, November 2). Do you love or loathe coffee? Your genes may be to blame. Retrieved from https://www.nationalgeographic.com/science/article/news-daylight-saving-time-coffee-caffeine-genes-dna

Yurii Brown

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