Why coffee sometimes makes you sleepy? Here's the science behind it

Are you still feeling drowsy even after sipping on multiple cups of coffee? Instead of feeling energized, you get sleepier. Strange as it may sound, there’s solid science behind it.

By Ankita Das

Sep 26, 2025 12:13 IST

Coffee is often the first thing many of us crave in the morning. Some grab it during work breaks, others to beat boredom. But there are exceptions. Many people have reported that after drinking coffee, instead of being them up, coffee makes them want to curl back into bed. Experts say there are clear biological reasons behind this.

Nutritionists say that coffee can also have the opposite effect on the body due to caffeine tolerance, changes in blood sugar levels and different metabolic rates from person to person. If you understand this, you can enjoy the fun of coffee. The real purpose of drinking coffee will be successful.

What causes you to fall asleep after drinking coffee?

1) Adenosine rebound

There is a chemical called adenosine in the brain. Fatigue is caused by this chemical. The function of coffee is to block the effect of this adenosine receptor. As a result, sleepiness and fatigue are easily eliminated. But the chemical called 'adenosine' does not stop secreting. He continues to accumulate in his own way. As soon as the effect of coffee is cut, fatigue is immediately surrounded.

2) Caffeine tolerance

If coffee is gradually turned from habit to addiction, its effect cannot be understood separately. The body makes friends with coffee. The brain also compromises with the adenosine receptor in its own way. As a result, caffeine cannot use its effect in any way. So instead of cutting fatigue, sleepiness comes upside down.

3) Lack of sleep

Drinking coffee just one or two hours before bedtime disrupts your natural sleep cycle. The following morning, you wake up late, feel dull, and lack alertness. Over time, this habit lowers your sleep quality and leaves you tired even if you sleep longer.

4) Stress hormones

Caffeine stimulates the secretion of stress hormones like cortisol and adrenaline. This gives you an instant burst of energy, but it does not last long. Once caffeine wears off, these hormone levels crash, leaving you feeling even more drained than before.

Prev Article
Insufficient sleep may contribute to heart problems and increased cancer risk
Next Article
Don’t like broccoli? Here are four Indian veggies with similar health benefits

Articles you may like: