Why does caffeine make me tired?

Coffee is arguably the world’s most popular drug, with millions of cups being guzzled every day. Whether you’re a sucker for Starbucks, or just enjoy making your own brew at home, it’s a great way of getting a quick fix of caffeine and kickstarting the day.

It’s a habit that’s easily acquired and devilishly hard to drop. But what if caffeine has started making you feel tired during the day though, rather than energised and alert?

There are a few likely causes of caffeine-fatigue. Not all are directly linked to the caffeine itself, but rather the way it changes the functioning of your body as a whole.

(Want to learn more about home coffee brewing? Take a look through my guide for other brewing methods, buying guides and more.)

Your brain on adenosine

Your body makes an important neurotransmitter called adenosine, which plays a crucial role in your wake/sleep cycle.

When you drink any product with caffeine in it, it’s believed that the adenosine receptors in your brain are temporarily blocked from receiving and absorbing it.

Here’s the kicker though. While your brain can no longer absorb adenosine, it’s still busy producing it.

That means when the effects of the caffeine wear off, your brain has a stash of adenosine it’s ready to absorb

The end result? Unexpected tiredness.

someone sleeping with their head on the table on a train

You’re becoming dehydrated

Caffeine is a diuretic which, in layman’s terms, means you wee more frequently.

The more you wee, the more water you’re losing from your body, and that can result in dehydration.

When you’re dehydrated, your blood pressure reduces. This by itself can leave you feeling drowsy.

Caffeine narrows the blood vessels in your body as well. That means there’s less blood flowing and so less oxygen moving around your body. Not good for energy levels.

One of the most obvious symptoms of dehydration is if your wee is darker than usual, or a little pungent.

The best solution? Have a glass of water for each cup of tea or coffee you drink during the day.

A lot of people struggle to drink the recommended amount of water every day, but it’s really important for good health.

It will also reduce the impact of fatigue brought on by caffeine. It’s a win-win habit that’s well worth getting into.

Too much sugar in your brew?

Another culprit may be the amount of sugar you consume with your caffeine.

If you’re fond of a particularly sweet cuppa, it’s possible you’re experience something known as hypoglycemia. This is also known as a sugar crash.

Fatigue is a key symptom in this regard, and it happens because your body processes the energy in the sugar faster than the caffeine.

Combined, the effects can be even worse if you’re also experiencing dehydration.

Four urinals in a public bathroom
You again?

Beat the cycle

All these problems compound each other, and you’ll find yourself in a vicious circle.

First you grab a coffee because you’re feeling tired, then you go to the bathroom. You lose liquid and so you feel dehydrated. That dehydration – and the loss of sugar from your coffee – makes you tired.

Guess what you do next to get back on an even keel?

Time to break that cycle. Here are some tips to consider if your caffeine’s making you more tired than energised.

  • To reduce caffeine fatigue, try reducing the amount of coffee you drink to around 2-4 cups a day. The Mayo Clinic recommends a maximum daily intake of 400 mg in any 24 hour period. This will help reduce your tolerance over time as well.
  • If you just can’t limit yourself to that much coffee, consider changing to decaf for part of the day. The afternoon’s best, as you’ll want to reduce your caffeine intake the nearer you get to sleeping.
  • Tea typically contains less caffeine than coffee, so think about switching in a few cups.
  • Caffeine used to be pretty much exclusive to coffee and tea but not any more. If you’re guzzling energy drinks at any point during the day, you’re likely taking in a lot of caffeine. Choose one or the other – or cut down on both – if you’re feeling drowsy.
  • If you’re a sugar junky, try reducing the amount you’re adding to your tea and coffee. It can be tough to adjust, but pledge to give it a try for a week or so. You might surprise yourself at just how quickly your tastebuds will adjust to the reduction.
  • If you’re using cheap or blended coffee, it may contain an unusual amount of a toxic chemical called mycotoxins. This alone can make you feel more tired. Try – even temporarily – a higher quality brand of coffee and see if that helps. If it does, you may need to increase your budget to maintain your caffeine fix.

Now you know why caffeine can make you unexpectedly tired! Make a few adjustments and there’s no reason why you can’t carry on enjoying your favourite cup of coffee.