I work overnight shifts (11pm-7am) and take caffeine pills to stay awake. When I get home, even if I take more caffeine I’m sometimes still too tired and fall asleep. Why does it eventually stop working? Is there some sort of chemical limit? Why can’t caffeine replace sleep for longer periods of time (like days on end)?
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Caffeine can help you stay awake and alert for a while, but it can’t fully replace the need for sleep because they work differently in your body.
When you’re awake for a long time, your body builds up a chemical called adenosine, which makes you feel tired. Caffeine blocks adenosine receptors in your brain, which is why it helps you stay awake by temporarily reducing that tired feeling.
However, your body keeps producing adenosine, and eventually, caffeine can’t block all of it. So, even if you take more caffeine, your body’s natural sleep drive becomes stronger, and you’ll feel extremely tired.
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