Stop caffeine earlier than you think you need to
Half of it is still in you six hours later, whether or not you feel it.
Do this
Set a cut-off eight to ten hours before bed. If you sleep at 11pm, that is early afternoon. Judge the change by sleep quality over a fortnight, not by whether you subjectively feel wired.
Why it works
Caffeine has a half-life of roughly five to six hours in most adults, and blocks adenosine receptors that build sleep pressure. A controlled study found 400mg taken even six hours before bed reduced total sleep time measurably, while participants did not notice the disruption.
Where it fails
Metabolism varies severalfold between people for genetic reasons, so a fixed rule fits nobody exactly. The 2013 study used a substantial dose; smaller amounts will matter less. Cutting caffeine also does nothing for insomnia driven by anxiety or an irregular schedule.
How you’ll know
Track sleep for two weeks with and without. The self-report is the unreliable part, so use time-to-fall-asleep rather than how rested you feel.