Caffeine Makes Me Tired – Is There Something Wrong With Me?

If you take several different medications, there’s a good chance that at least one of them didn’t work as expected. In that case, your doctor probably prescribed a different drug.

Why wouldn’t a prescription medication work? Quite simply, it’s because everyone’s body is different. Not everyone reacts to a drug in quite the same way.

(If you have doubt about that, just think about the different ways your friends may react to alcohol or weed.)

Caffeine is a drug, too. In fact, it’s the worlds’ most-popular psychoactive drug. But just as with all other drugs, not everyone reacts to caffeine in quite the same way.

Most of us down a cup of coffee, a soda or an energy drink to get the quick boost that caffeine usually provides. But for some people, caffeine actually seems to induce sluggishness, not alertness.

How can caffeine actually make you tired? Isn’t it a stimulant that promotes wakefulness?

Yes, it is. But there are other factors that could be in play.

What Caffeine Does In the Body

Ask people what caffeine is, and you’ll get answers like “it wakes you up,” “it makes you more alert,” or “it boosts your energy.”

But those are actually examples of what caffeine does. Here’s what it is: a stimulant that interacts with the central nervous system.

Much of the caffeine we consume is natural, produced by and extracted from plants like the coffee plant (which, of course, produces coffee beans), the tea plant (Camellia sinensis) or the cacao plant (which produces the cocoa beans used to make chocolate).

On the other hand, some of the caffeine now used in beverages like soda and energy drinks is man-made. The natural and artificial forms of caffeine are chemically identical, so they work in exactly the same way. 

There’s no “magic ingredient” in caffeine that gives you its trademark jolt of energy. Just as with all other stimulants, caffeine’s secret is the way it interacts with important chemicals in the brain. In this case, the most important chemical is known as adenosine.

A1 Adenosine Receptors

During the day, the body produces adenosine molecules. When we’re physically or mentally active, it produces more of them every hour.

Adenosine works like a neurotransmitter to carry signals throughout the brain – and one of the messages it carries is the need to rest. That’s why we get more and more tired as the day progresses; the body’s levels of adenosine continually increase.

Adenosine delivers its signals by binding to groups of receptors in the brain called, as you’d probably guess, adenosine receptors. After locking to some of them, the ones known as A1 receptors, adenosine sends messages throughout the brain and body to promote muscle relaxation and sleepiness. That’s part of the normal sleep-wake cycle.

But there’s one thing that can stop those “tiredness” messages from being delivered: caffeine.

Caffeine is able to act very much like adenosine, but it does so with a different purpose. It binds to the A1 receptors and blocks them. That prevents adenosine from binding to them and delivering its “you are getting very sleepy” message.

Instead, the stimulant makes sure you’re not getting tired – until the effects of caffeine wear off. That’s why a cup of coffee only keeps you juiced for a few hours, and a 5-Hour Energy only keeps you juiced for, well, about five hours.

A2A Adenosine Receptors

Adenosine binds to A2A receptors in the brain, too.

Unlike A1 receptors, A2A receptors don’t have anything to do with getting tired. They’re responsible for moderating the level of feel-good hormones and neurotransmitters, like serotonin and dopamine, released in the brain. They also moderate levels of adrenaline, the so-called fight-or-flight hormone.

As a stimulant, caffeine causes the release of serotonin, dopamine and adrenaline. But because caffeine blocks adenisone from attaching to the A2A receptors, it lets the surge of hormones course through the brain.

That’s why the caffeine in coffee or an energy drink makes us feel so good for a short time.

It doesn’t just cause the release of hormones and neurotransmitters that energize us and make us feel happy. It also protects them from adenosine – until caffeine unbinds from the receptors and is metabolized by the body.

Blood Vessels

The final important function of caffeine may seem to contradict what you’ve been told in the past.

There’s research showing that caffeine widens the blood vessels and increases blood flow in some parts of the body. This apparent vasodilation is one of the reasons why medical experts say that coffee is good for heart health.

However, things work very differently in the brain. Caffeine does just the opposite there, acting as a vasoconstrictor that causes blood vessels to contract and reducing blood flow. Why does that happen?

It’s because of our old friends, the A2A receptors.

When adenosine binds to them, they tell blood vessels to expand, in order to allow increased blood flow. But caffeine blocks those receptors – causing the blood vessels to contract instead of expand.

(Headaches are often caused when blood vessels in the brain expand and press against sensitive nerves. That’s why caffeine can help relieve headaches; it forces the vessels to contract, relieving pressure on the nerves.)

Why Caffeine Can Make You Feel Tired

Now that you know what caffeine does, let’s see why it sometimes appears to make people feel tired.

As it turns out, there are a number of possibilities.


Yep, here we are again, talking about adenosine.

You know that caffeine blocks the ability of adenosine to make us feel tired. But that adenosine doesn’t just give up and go home – it waits. In fact, the brain keeps producing it.

So when caffeine finally goes on its way, that build-up of adenosine attaches to the A1 receptors and can make you feel even more tired than you normally would. It’s similar to experiencing a sugar rush; the rush is almost always followed by a crash.

Speaking of Sugar…

It might seem that caffeine is making you tired, but what may really be hitting you is a sugar crash.

Many of us love our soda sweet, and our coffee loaded with sugar. Unfortunately, consuming lots of sugar – not to mention all of the yummy sweet stuff in coffee drinks – causes the body to produce higher levels of insulin.

In turn, the insulin causes blood sugar (glucose) levels to drop. And when blood sugar falls, we get tired, anxious and irritable.

Here’s what that means: we’re not necessarily sleepy because of the caffeine in caffeinated beverages. Our body is just crashing after an initial sugar rush. If you’ve had a Cinnabon or other sweet treat with your coffee, they can make the problem even worse.

One way to deal with the issue is to sweeten coffee with natural, non-nutritive sweeteners like monk fruit extract.

A good option is Super Coffee ready-to-drink keto-friendly coffee; it already contains monk fruit sweetener, as well as the MCT oil that helps keto dieters burn fat more efficiently while supplying extra energy.


The body can build a tolerance to almost any drug, and that includes caffeine. The more habituated you get to caffeine, the less of an effect it will have on your heart rate, your blood pressure, and importantly, your energy levels.

In other words, coffee won’t keep you awake in the same way it did before you started drinking a lot of it.

There’s an interesting twist, too. When you consume a large amount of caffeine each day and it regularly blocks the adenosine receptors, the brain responds by simply creating additional adenosine receptors. That can make it more and more difficult to get the same effect from coffee, tea, Coke or energy drinks.

How do you overcome caffeine tolerance? The best way is to completely eliminate it from your daily routine for a while.

Probably more reasonable for a coffee lover: reduce your caffeine consumption by switching from black coffee, espresso or other caffeinated beverages, to water, fruit juice or decaf (which only contains a fraction of the caffeine in coffee).

When you go back to your coffee or caffeinated soda, not only will the tolerance issue be eased – but you’ll appreciate the caffeine more than ever.

There’s a catch-22 to be aware of, though, and it’s one you may have experienced.

If you drink coffee regularly and then stop abruptly, you could suffer what’s known as caffeine withdrawal. Like any type of drug withdrawal, it can produce side effects like irritability, headache – and, you guessed it, fatigue. The issues can be avoided by cutting back gradually instead of going cold turkey.


One of the well-known effects of coffee is that can produce diuretic effects. That’s a polite way of saying it makes you pee more than usual. The effect really shows itself in heavy coffee drinkers once they go past three or four cups of coffee per day.

When you urinate a lot, you’re likely to be losing more fluid than you’re consuming – and that can make you dehydrated, which may cause dizziness, dry mouth and – yes - fatigue.

If it feels like caffeine is making you more tired than usual, try drinking more water than usual. Eating foods that contain lots of water, like vegetables and fruit, can help you get enough water into your body as well.

Or, of course, you could just reduce the amount of coffee you drink each day.


When you’re stressed or anxious, your body goes on high alert and releases the stress hormone cortisol and the “fight-or-flight” hormone epinephrine (better known as adrenaline). Those hormones cause the increase in heart rate and blood pressure that we’ve all experienced under stress.

Immediately after the stress or anxiety is relieved, you don’t just feel “better” – you’re also likely to feel more tired than usual.

Guess what drinking coffee and other caffeinated beverages does? It induces the body to produce more cortisol and adrenaline.

A study at The Ohio State University found that caffeine intake, from any source, doubles the body’s natural levels of the hormones. So a cup of joe or an energy drink may actually make your body feel stressed, and its natural reaction once the caffeine wears off is to feel tired. The effect is even more pronounced in those with pre-existing stress and anxiety issues.


Coffee beans are prone to growing mold – and mold often produces toxic compounds called mycotoxins.

In most cases, the level of mycotoxins in coffee is considered “safe.” But here’s the problem: mycotoxins can cause chronic fatigue.

You’re not going to do a lab analysis on your coffee before drinking it, needless to say. It’s smart, however, to make sure the coffee you drink is as fresh as possible; otherwise it might seem that caffeine is making you tired, when the culprit is really microfungi.

Caffeinated beverages can unquestionably deliver a quick jolt of energy. Coffee and tea, in particular, provide a number of health and wellness benefits as well.

But to ensure that your caffeine boost doesn’t wind up actually making tired, pay attention to the other factors that can negate the alertness and wakefulness you expect when pouring that morning cup of coffee.

Written by Jordan DeCicco


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