Why that one cup of coffee isn’t the problem

You stack more caffeine in a day than you think, because it’s in more products than you realize

Caffeine doesn’t affect everyone the same way. While one person can fall asleep easily after an espresso, another may toss and turn for hours. That difference comes down to biology. How sensitive you are to caffeine depends on your metabolism, liver function, and genes.

The average half-life of caffeine is between five and seven hours, but for some people it can extend to nine or even ten hours. This means that a cup of coffee at 3 PM can still be noticeable in your body at 12 PM.

The average half-life of caffeine for some people can extend to nine or even ten hours

Je voelt dat meestal niet als ‘wakker’. Het is subtieler. Je zenuwstelsel blijft net iets te actief, alsof de motor nog draait, terwijl je al in bed ligt. En slaap houdt niet van een systeem dat half gas blijft geven.

Caffeine is in more products than you think

You usually don’t feel it as being ‘wide awake.’ It’s more subtle. Your nervous system stays just a bit too active, as if the engine is still running while you’re already in bed. And sleep doesn’t like a system that keeps running at half speed.

What makes caffeine sneaky is that it’s in more products than you realize. Many people only think of coffee, but tea, cola, energy drinks, chocolate, and even some workout supplements and painkillers also contain caffeine. Together, they can add up to a stack bigger than you expect—and that your body still has to deal with at night.

Below is an overview of products that contain (a lot of) caffeine, with examples and their estimated caffeine content. I’ve compared this to a standard cup of filter coffee (200 ml ≈ 90 mg of caffeine). For younger readers who can’t picture filter coffee: a café latte with one espresso (30 ml) contains about 63 mg of caffeine. If the latte has a double espresso, that can rise to around ±120 mg.

Product	Caffeine	= Number of cups of coffee
Energy drinks	80 – 180 mg	1 - 2
Cola (normal)	32 - 35 mg	1/3
Fritz-Kola	80 mg	1
Black tea	40 – 50 mg	1/2
Green tea	25 – 35 mg	1/4 tot 1/3
Matcha	60 - 70 mg	0,6 tot 0,7
Dark chocolate (50 g)	20 – 25 mg	1/4
Milk chocolate (50 g)	10 mg	1/10
Tiramisu	20 - 30 mg	1/5 tot 1/3
Painkillers with cafeïne	50 - 65 mg	1/2 tot 2/3
Kombucha	10 - 25 mg	1/10 tot 1/4
1 gram guarana powder	40 - 50 mg	1/2
Mate-tea	30 - 50 mg	1/3 tot 1/2
Pre-workout supplement	150 - 200 mg	1,5 tot 2

Stacked caffeine can affect your sleep in several ways. Falling asleep may take longer, sleep can become lighter, and you might wake up before your alarm. It can also make racing thoughts faster and more intense, which doesn’t help with falling or staying asleep. An important insight here is that you can feel sleepy while also being overactivated. This feels like a restless body, rapid thoughts, and the sense of being exhausted but unable to switch off.

For healthy adults, a common safe upper limit is around 400 milligrams of caffeine per day. For poor sleepers, that limit is usually lower, as their nervous system is more sensitive to stimulation.

How much caffeine is right for you?

To find out what works for you, it helps to test out of curiosity. A simple way is to avoid all caffeine for seven days. During that week, track how quickly you fall asleep, how often you wake up, and how rested you feel. You can use a sleep diary for this—email me and I can send you one. Headaches or drowsiness in the first few days is normal.

After that week, start reintroducing caffeine. Begin with one cup in the early morning, for example around 8 AM. If that goes well, test a week later what happens if you have the same amount around early afternoon. Pay attention not just to whether you fall asleep, but to subtleties: how light your sleep is, how early you wake up, and how calm your mind feels. That pattern tells you more than any guideline ever will. You can track this in a sleep diary.

For many poor sleepers, caffeine is least disruptive when they stop eight to ten hours before bedtime, or when they limit it to the morning. The comfortable daily amount often falls between 100 and 150 milligrams. This isn’t a rule, but a common outcome.

Caffeine isn’t the enemy. By understanding how it accumulates and how your body responds, you can make room for rest without giving it all up.”