Its levels are fairly low by the time you're fully awake, but they slowly build throughout the day. In turn, this triggers pathways that slow neural activity and increase feelings of sleepiness.Īdenosine levels in your brain fluctuate. By binding to adenosine receptors in your brain, adenosine activates the receptors. It's able to do so because - as far as molecular structures are concerned - caffeine looks very similar to one of the naturally occurring molecules in your body that typically binds to these receptors, called adenosine.Īdenosine plays many roles - including helping to regulate your sleep/wake cycle. It's here that caffeine elicits its most classic effect - helping keep you alert and awake.Ĭaffeine accomplishes this by blocking sleep-promoting receptors in your brain called adenosine receptors. Once consumed, caffeine is very quickly absorbed and distributed throughout your body, including to your brain. So, when it comes to that gray area between late morning and early evening, how late is too late to drink that afternoon coffee you so desperately need - or even just a soda or iced tea with dinner - without it affecting your sleep? How does caffeine work? And, at the time, it felt like you needed it just as much as the sleep you're not getting now.

(Right before bed, for instance.just in case.)īut, you needed that caffeinated pick-me-up to get through the rest of your busy, exhausting day. You know caffeine can keep you awake, and there are the obvious times to avoid it. Or, maybe you're counting the number of hours you might get if you fell asleep right now.

Specifically, the number of hours you're not getting. Instead of counting sheep you're counting hours of sleep.

You have that effect on me