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Caffeine Doesn’t Affect Me

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By Matt Woodburn-Simmonds

When it comes to the effects of caffeine, there are several types of people in the world:

  • Some people feel like they cannot function as a human until they have had their morning caffeine fix.
  • Others will turn into a jittery wreck if they stray beyond the caffeine levels of “half-caf” coffee.
  • Then there are those who guzzle 10+ cups of coffee a day and have an espresso an hour before going to sleep without noticing any real effects at all.

This is all really weird, and kind of annoying for many people, especially if you need a pick-me-up and are left wondering why the caffeine is having no effect.

So why does caffeine affect people so differently? What are the reasons that caffeine doesn’t affect me? Read on as we uncover the 4 reasons, and what you can do about it.

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Women asleep at desk: 4 reasons why caffeine doesn't affect me
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What is Caffeine and How Does it Work?

First thing first, what is this magical component of coffee?

Caffeine is a bitter-tasting, psychoactive substance. Sounds like fun, doesn’t it?

Psychoactive just means that it affects how the brain works. Caffeine affects the adenosine receptors in your brain (the parts of your brain that pass and receive the messages that make you work).

When you drink coffee, caffeine likes to fill these receptors up which blocks the adenosine from binding to them and sending signals.

So, think about sending an email. Your boss has sent the message, but your computer is turned off. This is what the caffeine does – turns off the receiver.

It might sound like the kind of thing that would make your brain less active, not more. However, these adenosine pathways are actually there to make you sleepy, so having caffeine in the way keeps you more alert. Like how you get much more done when not tied to your inbox.

As the caffeine is broken down by your body, this frees up these A1 adenosine receptors allowing adenosine to bind to them again, making you sleepy.

The caffeine content of your final cup of coffee will vary depending on your preferred brewing technique, size, and coffee beans used.

Infographic displaying the top facts about caffeine and coffee
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Why Does Caffeine Affect People Differently?

The overly simplistic answer is that because we are all different.

Our biology is subtly different meaning that many factors affect how caffeine interacts with your A1 adenosine receptors and how it is metabolized. Here we’ve listed the biggest factors in caffeine variation to help you answer ‘why does caffeine not affect me’.

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4 Reasons Caffeine Doesn’t Affect Me


All humans share 99.9% of our genetic code so the genetic differences between us are ridiculously small.

However, within these small differences, there can be variations in our sensitivity to certain substances including caffeine.

So, if caffeine doesn’t affect you, there could be some genetic reasons:

In fact, there are 8 genetic variants linked to caffeine consumption, 6 of which were identified by the Harvard School of Public Health. 4 specifically affect caffeine metabolism, 2 control the rewarding effects, and the last 2 are connected to cholesterol and blood sugar.

So, maybe your adenosine A1 receptors are a subtly different shape and caffeine doesn’t bind to them as well, rendering it less effective.

Or, perhaps you produce more enzymes that can break down caffeine, greatly reducing the time it is bound to the receptors and thus, its efficacy.

The main enzyme for caffeine metabolism is CYP1A2. Variants of this enzyme can speed up or slow down how fast your body metabolizes caffeine.

So, if caffeine has no effect on you, you might need to lay the blame at your parents’ feet.

You’re Too Used To It

Once upon a time, did drinking coffee give you a buzz? But now nothing brings that energized feeling, no matter how many espressos you drink?

If yes, it’s because our bodies build up caffeine tolerance fairly quickly. Without even noticing, you probably moved from 1 coffee a day to 2, then 3. And before you know it, you’re drinking several cups every day.

Whilst you may no longer be feeling the highs of caffeine, it is absolutely still in your body. So, if you stop drinking it, caffeine withdrawal will kick in and you will feel pretty horrific for a while.

Along with caffeine tolerance comes caffeine dependence:

Your body is so used to being flooded with caffeine that if you take it away, you’re suddenly in all sorts of trouble. So, if you’re no longer feeling the good side of caffeine, don’t go cold turkey. Slowly dial back your caffeine intake – try and reduce it to 1 or 2 cups per day.

After doing this, hopefully, a 3rd would add the boost you are after.

I have several friends who have gone cold turkey on caffeine and described it as “like quitting smoking turned up to 1000”. So please be careful.

You’re a Smoker

Interestingly, smoking increases the speed of caffeine metabolism in your body.

If you’re a smoker who doesn’t feel the effects of your morning brew then your other morning habit probably has something to do with it.

Stopping smoking is good for many health reasons. And, whilst increasing the buzz you get from your coffee isn’t very high on that list, it is still something else to think about.

Lack of Sleep

“Coffee is sleep for those without enough free time”

This font of knowledge was repeated to me by the manager at my first barista job when I complained about my totally self-inflicted lack of sleep. But, unfortunately, there is little truth in it:

If you’re not getting enough sleep, no amount of caffeine will make you alert.

Lack of sleep affects us in many ways and caffeine only works on a small number of pathways within the brain. Slamming obscene amounts of caffeine at your brain will not compensate for the fact you went to sleep at 5am and got up for work at 7am. Even less so if this is more of a chronic issue and you’ve only been sleeping 3 hours per night for an extended period of time.

Whilst caffeine isn’t a miracle cure – a good night’s sleep will do more good than a good coffee – 8 hours per night just isn’t feasible for everyone. Instead, try taking a coffee nap:

Drink your cup of joe then nap for no more than 15 to 20-minutes. This frees up your adenosine receptors to the caffeine so that when you wake, you feel energized.

Person jumping for joy from the alternative ways to energize yourself if caffeine doesn't affect you
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Other Ways to Feel Energized Without Caffeine

If you’re just someone who doesn’t get the kick that you need from caffeine, what can you do instead?

Stay Hydrated

I know, I know. You’ve heard it a million times before but drinking water is good for you.

Aside from the parental nagging, keeping hydrated can also keep you alert. When you are dehydrated, your blood pressure can drop and generally leave you feeling fatigued.

Make sure you always have a water bottle handy when at work and try starting your day with a pint of cold water instead of coffee. You’ll be surprised how well it works.

Let in the Sun

Vitamin D – the sunshine vitamin – is a micronutrient our bodies create with exposure to sunlight.

A lack of vitamin D can make us lethargic – just ask anyone who lives in the north with the short, winter days. Getting more sunlight can help boost your energy levels, and you’ll probably feel happier too. So take a walk, throw open the blinds, or get a light therapy lamp.

Take a Nap

The Europeans are really onto something:

A 20-40 minute nap (or siesta) after lunch can dispel that post-eating lethargy. It doesn’t need to take long, 20-40 minutes is the optimal amount of time to feel rested without waking up wondering what day of the week it is. I hope your office has somewhere quiet and comfy.

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The Verdict to Why Caffeine Doesn’t Affect Me

Being unaffected by caffeine is fairly common and is probably a combination of multiple factors listed here, not just one. After all, it’s not a miracle cure for sleepiness.

So, if you find yourself questioning “why caffeine doesn’t affect me” and craving the jolt of energy, try looking for alternative ways to perk yourself up.

No matter what your preferred caffeine source is – cold brew, espresso, French press, tea, or energy drinks – if you are no longer feeling the benefit, try dialing it back a little over time. Then, add back in the occasional extra cup to try and get the much-needed boost.


Matt Woodburn-Simmonds

Matt's coffee obsession started in 2006 when working as a Barista. A tendency to turn up to work hungover kickstarted his coffee journey which quickly turned into a love affair. As he moved on to work as a Restaurant Manager and Sommelier, the obsession continued to grow. Now, his passion is helping others to enjoy better coffee at home.

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