MUNDANE MYSTERIES: Why Does Coffee Seem To Make Some People Sleepy?

Ever notice how coffee seems to make some people sleepy? Why is that? I mean, with all the caffeine that’s in coffee, providing coffee with its reputation as a way to jolt yourself into staying awake, feeling sleepy after a cup of coffee doesn’t really make sense. But plenty of people swear their afternoon espresso shot does the opposite of what it’s supposed to do. And, if you happen to be one of those people, just know this: you’re not crazy.

A neurochemical called adenosine is the reason we get tired throughout the day. Adenosine builds up & passes through receptors, making your nerve cells become less active & the blood vessels in your brain to dilate. Basically, what your body hears at that point is, “Hey, it’s time to rest”. But, since caffeine resembles adenosine, after you drink coffee the caffeine binds to those receptors instead, blocking the real adenosine from passing through, thus preventing your body from slowing down.

Caffeine can keep you awake like that for a little while, but it doesn’t get rid of all your adenosine forever. So, when your caffeine kick inevitably wears off, you end up with an adenosine buildup that makes you feel even more tired. It’s a lot like when you get a burst of energy after eating something sugary, only to crash not long after. And, speaking of sugar, if your coffee mix involves lots of it, that could add to your post-coffee fatigue, as well. There’s also the possibility that caffeine’s diuretic quality causes dehydration, which can make you feel tired.

One other reason you might feel tired after coffee: you may have built up a high tolerance for caffeine, so much so that a cup of coffee doesn’t perk you up like it once did. Sadly, the best way to fix that is to cut back your daily coffee intake.

Got a Mundane Mystery you’d like solved? Send me a message via social media (@AndyWebbRadioVoice), or shoot me an email at

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