Explaining why someone is more sensitive to caffeine after quitting smoking

Coffee mug with no smoking sign

Almost no one gets told about this when they quit smoking. And, I’m convinced that not knowing about it could directly result in some people struggling to quit.

So, let’s cover why someone would be more sensitive to caffeine after quitting smoking.

Caffeine and smoking cigarettes

Nicotine and caffeine are both stimulants that will act on the same parts of the brain (just in different ways). It’s estimated that up to 86% of smokers will also drink significant amounts of caffeine (mostly in the form of coffee). Not only will they consume more, but there is also a link between drinking caffeine and smoking. In those who smoke, they will be 55% more likely to smoke while drinking a caffeinated beverage.

Smoking’s effects on the body

No, I’m not going to list all the dangers of smoking. I don’t want to make this post longer than it needs to be. Plus, I don’t think there’s any great mystery that smoking is bad for you.

What I want to talk about is what smoking does to how your body can metabolize (i.e. “process”) certain substances.

When someone smokes, it will increase the activity of a certain enzyme. I don’t expect you to remember the name of the enzyme (CYP1A2), nor really care about it. What is important to know is that this enzyme is how the body processes some substances, including caffeine.

Increasing the activity of this enzyme helps metabolize caffeine faster. This is why people who smoke tend to drink up to 4 times as much caffeine as non-smokers.

These enzymes are essentially like little factories that will process caffeine to allow our bodies to get rid of it.

When you’re smoking, it’s like all of a sudden you have 2 to 4 times as many factories as there were before. Now that your body can process more caffeine, you need to consume way more to achieve the same effects.

Not just cigarettes

It’s not the products in the cigarette that cause this impact on caffeine metabolism; it’s act the smoking that is causing it.

So, the content of this post would also apply to people who are smoking cannabis.

As far as vaping is concerned, there does not seem to be any impact on the processing of caffeine. It’s really only seen in those who smoke.

What will happen when you quit smoking?

Once you’ve quit smoking, these “factories” will eventually go back to what we would see in a non-smoker. This means your body isn’t processing as much caffeine; which will lead to much higher levels of caffeine in your body. I know I’ve already used one analogy, but let’s make it two:

So…Think of it as a bath tub when you have a shower. If the drain is working very well (like in smokers who can process, or “drain” the caffeine faster), then no water will accumulate in the tub.

But, if the drain all of a sudden isn’t working as well (like when smokers quit and the “draining” of caffeine decreases)… then, if you keep putting in water at the same rate, it can start accumulating in the tub .

When this was studied in the 1980s and 1990s they observed that after someone stopped smoking, if they kept drinking the same amount of caffeine, the levels of caffeine in their body would go way up. One study found it would increase by 203% at 3 weeks post-quitting and another observed a whopping 269% increase of caffeine levels at 12 weeks post-quitting.

OK, so I have more caffeine in my body…what’s the big deal?

The problem with all of a sudden having loads of extra caffeine in your body is that you can start having side effects from this excess caffeine. This is particularly bad when you are trying to quit smoking cigarettes. This is because some of the excess caffeine symptoms could mimic nicotine withdrawal.

Here’s a look at just how well some nicotine withdrawal symptoms overlap with the effects of having too much caffeine:

Side effectNicotine

As you can see, many of the bothersome symptoms of nicotine withdrawal can also be seen from having too much caffeine.

Do you see the problem?

Symptoms of excess caffeine could appear in people who continue drinking the same amount of caffeine after they’ve quit smoking cigarettes. The problem is that most people are not aware of this, and will attribute these symptoms to nicotine withdrawal.

Then, once they start smoking again, the boosted “factories” to process more caffeine get to work again, and the caffeine levels go back down. Now, once they feel better, they will also attribute this to smoking.

What can I do?

If you’re currently quitting smoking (or planning to) and also drink lots of caffeine (not just coffee, but any caffeinated beverage), then you should cut your caffeine consumption in half. Otherwise, you could start seeing some side effects of excess caffeine.

For coffee, an easy way to do this in a way that doesn’t disrupt your routine too much is to either:
-switch half your coffees to decaf
-mix half decaf/half regular coffee.


When you smoke, your body can process much more caffeine than a non-smoker. After you quit smoking, this increased processing capacity will go back down to normal levels. This means your body can’t keep up with the amount of caffeine being ingested and caffeine levels will increase significantly. This increase can lead to side effects that mimic common nicotine withdrawal symptoms (such as irritability and anxiety).

If you drink lots of coffee (or other caffeinated beverages), and you are trying to quit smoking: make sure that you cut back on the caffeine once you quit.

Need help quitting smoking? Using nicotine replacement therapy can be a big help; check out my other article on nicotine replacement therapy here.

Dan Landry

Daniel (Dan) Landry, founder of Rxplanation.com, is an infectious diseases pharmacist at the Dr-Georges-L.-Dumont University Hospital Centre in Moncton, NB, Canada.

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