Early afternoon is the default cutoff because caffeine's effects last for hours after the cup.
The NHS lists caffeine among the most common causes of insomnia, and the FDA counts insomnia and sleep disruption among too-much symptoms, while noting people metabolize caffeine at very different speeds. Find your line by experiment: start at 2pm, and if you still lie awake, pull it back to noon for two weeks. Count tea, cola, energy drinks, and pre-workout in the total. If sleep is already broken, try two caffeine-free weeks, then reintroduce it at mornings only.
What to do
Common questions
When should I stop drinking caffeine?
Early afternoon is the right default for most people, and the more caffeine-sensitive you are, the earlier the cutoff. Caffeine has a half-life of several hours, meaning a 4pm double shot still has a meaningful amount circulating at 10pm, blocking the sleepiness signal your brain needs to start the night. The NHS lists caffeine among the most common causes of insomnia, and the FDA lists insomnia and sleep disruptions among the signs of too much caffeine, while noting wide variation in how fast people metabolize it. The practical method: if you fall asleep fine, a 2pm cutoff probably works; if you lie awake, move it back to noon for two weeks and see. Fast metabolizers can sometimes drink coffee with dinner, slow ones cannot touch it after breakfast, and you find out which one you are by experiment, not by vibe. Count the hidden sources too: tea, cola, energy drinks, pre-workout, and chocolate all push the daily total, and the FDA's 400 milligram daily guide for most adults covers all of them. If your sleep is already broken, the kindest experiment is a full caffeine holiday for two weeks, then a reintroduction at mornings only.