For many of us, the day doesn’t truly begin until we’ve had that first glorious cup of coffee. Whether you’re a flat white fanatic, a tea devotee, or partial to a cheeky energy drink, caffeine is the world’s most popular pick-me-up.
But have you ever noticed that, instead of feeling energised, you sometimes end up feeling even more tired after your morning cuppa? If so, you’re not alone—and there’s some fascinating science behind why this happens.
Caffeine is a natural stimulant found in coffee, tea, chocolate, and even some medicines. Its main job is to block a chemical in your brain called adenosine, which is responsible for making you feel sleepy.
By attaching itself to adenosine receptors, caffeine tricks your brain into thinking you’re not tired, giving you that familiar burst of alertness and energy.
But here’s the catch: this effect is only temporary. Your body absorbs caffeine quickly—within about 45 minutes of drinking your coffee, you’ll feel its full effects. However, after about five hours (sometimes less, depending on your metabolism), the caffeine starts to wear off.
When that happens, all the adenosine that’s been building up in the background suddenly floods your system, making you feel even more tired than before. This is what’s known as a ‘caffeine crash’.
If you find yourself reaching for a second (or third) cup just to get through the day, you might be caught in a classic caffeine cycle. Here’s how it works:
1. You drink caffeine to feel awake.
2. The caffeine wears off, and you crash—feeling even more tired.
3. You drink more caffeine to fight the fatigue.
4. Repeat!
Over time, this cycle can actually make you more tired overall, especially if you’re not getting enough quality sleep at night. Caffeine can stay in your system for up to 8 hours, so having a cuppa too late in the day can make it harder to fall asleep, leading to grogginess the next morning—and the cycle continues.
Caffeine doesn’t just block adenosine; it also triggers the release of adrenaline, the ‘fight or flight’ hormone. This can make you feel more alert, but too much caffeine can tip you over into feeling jittery, anxious, or even panicky. After this adrenaline rush wears off, your body needs to recover, which can leave you feeling even more drained.
Drinking too much caffeine can disrupt your sleep, making it harder to fall asleep and even causing insomnia if consumed too late in the day. This often leads to waking up groggy and reaching for more caffeine, creating a cycle of fatigue and dependence. To support better sleep, it’s best to cut off caffeine by early afternoon.
If you’re sensitive to caffeine or prone to anxiety, it’s worth keeping an eye on how much you’re consuming. Symptoms like a racing heart, sweaty palms, or feeling on edge could be signs you’ve had a bit too much.
Like many things in life, your body can get used to caffeine. The more you drink, the more adenosine receptors your brain creates, which means you need more caffeine to get the same effect. This is why that first cup of coffee as a teenager felt like rocket fuel, but now it barely makes a dent!
If you suddenly cut back or skip your usual dose, you might experience withdrawal symptoms like headaches, irritability, trouble concentrating, and—you guessed it—fatigue. These symptoms can start as soon as 12 hours after your last cup and usually peak within a day or two.
Everyone’s tolerance is different, but the general guideline from health experts is to keep your intake below 400mg per day (that’s about four or five standard cups of coffee). For some people, even less is better—especially if you’re sensitive to caffeine, pregnant, or have certain health conditions.
If you find yourself feeling tired after caffeine, try cutting back gradually, switching to decaf (which still contains a small amount of caffeine), or opting for herbal teas.
While some coffee enthusiasts may shy away from decaf, switching to caffeine-free or decaffeinated options can be a helpful step if you’re trying to reduce your caffeine intake.
It’s worth noting the difference between the two: caffeine-free drinks contain no caffeine at all, while decaffeinated beverages still contain small amounts—typically around 15 milligrams or less per serving.
Caffeine can be a helpful tool for boosting alertness and getting through a busy day, but it’s not a magic bullet. Too much can leave you feeling more tired, anxious, or even disrupt your sleep. The key is to find the right balance for your body and lifestyle.
Have you ever noticed that your morning coffee leaves you feeling more tired than energised? Do you have any tips for managing your caffeine intake? Share your experiences and advice in the comments below.
Also read: When you drink too much coffee, this happens to your body—are you at risk?
