Dr. Trisha Pasricha advises that the last cup of coffee should be consumed about nine hours before going to sleep [1].

This timing is critical because caffeine remains in the system for several hours. If consumed too close to bedtime, the stimulant can disrupt sleep quality and prevent the body from entering deeper stages of rest [1].

Pasricha is a physician at Beth Israel Deaconess Medical Center and an assistant professor of medicine at Harvard Medical School [1]. In a video for The Washington Post, she said the lingering effects of caffeine impact the human body.

"Your last cup, researchers have found, needs to be about nine hours before you sleep," Pasricha said [1].

While Pasricha suggests a nine-hour window, other health reports provide slightly different benchmarks. An MSN Health article suggests that people stop drinking coffee at least eight hours before they go to bed [2]. This discrepancy highlights the varying rates at which individuals metabolize caffeine, a process that can differ based on genetics and overall health.

Coffee remains a dominant beverage globally. For context, some reports estimate annual coffee consumption in the UK reaches 98 million cups [3]. Given the prevalence of the drink, adjusting the timing of the final dose could have a widespread impact on public sleep hygiene.

Medical professionals emphasize that caffeine blocks adenosine receptors in the brain. Adenosine is the chemical that builds up during the day to signal to the body that it is time to sleep. By blocking these receptors, caffeine tricks the brain into staying alert even when the body is physically exhausted [1].

“"Your last cup, researchers have found, needs to be about nine hours before you sleep."”

The recommendation to limit caffeine nearly half a day before sleep reflects a growing medical focus on 'sleep hygiene.' Because caffeine has a half-life that varies by individual, a standard eight- or nine-hour cutoff serves as a conservative baseline to ensure the stimulant is sufficiently cleared from the bloodstream before the sleep cycle begins.