Last Updated: 29th September 2021

How Long Does Caffeine Stay in Your System? (Effects Explained)

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    Exactly how long does caffeine stay in your system? Research shows that caffeine can stay in our systems for up to 10 hours, but its impact on our bodies is more complicated than that.

    As a chemical stimulant that’s derived from plants, caffeine works by blocking adenosine receptors which are responsible for drowsiness.

    Adenosine is essential for the body since it’s responsible for initiating the first stages of sleep. But these chemical signals to the brain are less than desirable when they cause drowsiness at work.

    Caffeine prevents such drowsiness by temporarily blocking your brain’s adenosine receptors. This is what causes the sensation of an energy boost.

    With all of this, it’s no wonder that caffeine consumption is a global phenomenon. Britain alone is one of the highest caffeine consumers in the world.

    It is estimated that 80% of UK households buy coffee to drink at home. And approximately 95 million cups of coffee are drunk per day across the UK.

    Many view caffeine as an absolute essential that’s on a par with oxygen and water. But not everyone is fully aware of the key impacts caffeine has on our bodies or for how long they last. So keep reading to find out more!

    In short

    • Caffeine reaches its half-life within 5 hours of consumption. This means that by the five-hour mark, half of the caffeine you have consumed has been processed. So it can take as long as 6-10 hours for caffeine to fully leave your bloodstream.
    • The exact amount of time it takes to metabolise caffeine differs from person to person.
    • When taken six hours before bed, caffeine delays the onset of sleep and reduces sleep quality.
    • Caffeine is also found in foods and beverages other than coffee, such as chocolate and granola bars, fizzy drinks, and energy drinks.
    • There are now caffeine alternatives that have a coffee-like taste but use adaptogens as natural stimulants instead.
    • Caffeine is a natural stimulant that serves no nutritional function. We can choose to completely cut it out of our diets if it adversely affects our sleep.

    How Long Does Caffeine Stay in Your System?

    While we feel the effects of caffeine within as little as 30 minutes of consuming it, caffeine stays in our system for at least several hours at a time.

    Factors like individual metabolisms will vary from person-to-person.

    So the exact time it takes for each body to process caffeine will be different. And there will always be people that can sleep regardless of late-night caffeine, but science suggests these people are few and far between.

    For the majority of us, consuming caffeine in the evening will disturb our sleep cycles.

    The American Academy of Sleep found that on average, caffeine reaches its half-life within 3-5 hours of consumption.

    In other words, half of the caffeine you originally consumed will still be in your bloodstream 3-5 hours later.

    Two coffee cups with afternoon sunlight shining on them

    So if you had 40 mg of caffeine—which is about one cup’s worth of coffee—at 05:00 PM, there’s a good chance 20 mg of caffeine will still be in your system at 10:00 PM as you go to bed.

    All of this means that it could take anywhere between 6-10 hours for your body to fully process the consumed caffeine.

    So keep this in mind when deciding whether to brew yourself another cup or not!

    How Long Does Caffeine Keep You Awake?

    The adverse effects on sleep is perhaps the biggest drawback to caffeine consumption.

    The more caffeine you drink in the day, the more likely it is to affect your sleep, leaving you feeling more tired and consequently drinking more caffeine the next day.

    A study found that caffeine taken 3-6 hours before bedtime significantly affects sleep disturbance.

    The researchers found that caffeine still significantly reduced sleep time even when taken 6 hours before bedtime compared to participants who had consumed no caffeine at all.

    The rule of no caffeine in the six hours before bedtime has become widely accepted. But it seems that 6 hours should actually be the minimum amount of time.

    And if you really want to prevent it from affecting your sleep, your last cup of coffee or tea should be 11-12 hours before your usual bedtime.

    blurry sleepy man at desk coffee in foreground

    Caffeine affects, not just the amount of time you’re asleep, but also the quality of your sleep.

    The study found higher amounts of wake time throughout the night in the participants who had caffeine 3-6 hours prior. A reduction in the duration of slow-wave sleep (or “deep sleep”) was also observed in all participants who had consumed caffeine.

    Caffeine has also been found to throw off the body’s circadian clock—an internal set of signals that regulates the body’s 24-hour sleep-wake cycle. Researchers found that caffeine offset the participants’ internal clock by 40 minutes and delayed their sleep.

    Your circadian rhythm is supposed to reset depending on factors like your exposure to light and the release of chemical signals. For example, the release of adenosine is vital to falling asleep and resetting your body clock.

    But since caffeine naturally blocks your adenosine receptors, your ability to reset your circadian rhythm is hindered and is thus even further offset.

    There is no exact calculation as to how long caffeine will keep you awake.

    What is clear is that caffeine does delay sleep, lower sleep quality, and disrupt your body clock.

    But don’t throw all your coffee away just yet! Instead, focus on monitoring your daily caffeine intake.

    Find out how much caffeine your drinks contain and make adjustments.

    Further lower your intake by using a smaller cup for your usual mid-afternoon coffee break.

    If you’re still experiencing trouble sleeping, then aim to keep a minimum of 6 hours between your last caffeinated drink and your usual bedtime.

    You could also choose decaffeinated coffee alternatives so that you can still enjoy a delicious cup whenever you want. It may be hard to make these adjustments, but your body will thank you for them.

    What Food and Drinks Contain Caffeine?

    Aside from coffee-related foods like coffee cake and tiramisu, other surprising foods contain caffeine, such as chocolate, granola bars, and even some fruits like guarana berries.

    Snacks and processed foods containing chocolate will also contain caffeine. This includes cereal, puddings, cookies, chocolate yoghurt and so on.

    Caffeine is also found in certain painkillers and breath refreshers.

    Protein shakes also typically contain caffeine. But determining exactly how much is difficult since they are powdered.

    The FDA and the American Academy of Sleep Medicine advise consumers to avoid powdered pure caffeine.

    It probably won’t come as a surprise either that energy drinks contain large amounts of caffeine.

    In fact, energy drinks have significantly higher caffeine content than regular coffee drinks.

    Fizzy drinks like Coke, Pepsi, Mountain Dew, and Sprite all contain a substantial amount of caffeine as well.

    Even Matcha green tea has nearly as much caffeine in it as a regular 8 oz coffee. And remember that decaf coffee and tea still have 3% of their original caffeine content.

    How to Reduce Your Caffeine Intake

    The level of caffeine depends on many factors. Examples include:

    • the size of the tea bag or coffee bag you use
    • the size of your coffee cup
    • the type of coffee bean that’s been used for your coffee grounds. For example, Robusta has a much higher caffeine content than Arabica.

    It is recommended to limit your caffeine consumption to 300-400 mg per day. This is equivalent to about three to four 8 oz cups of coffee.

    top view of four coffee mugs on wooden table

    The average coffee cup is 8-10 oz. So if you usually drink from a cup that’s larger than average, cutting down to three coffees a day—or less—would be wise.

    If you usually drink Robusta coffee, switch to Liberica or Arabica coffee beans to decrease your average caffeine intake. Arabica coffee beans are thought to contain 1.5% caffeine compared to the significantly larger 2.7% found in Robusta.

    Aim to avoid energy drinks and snacks containing caffeine, like chocolate and granola bars.

    If warm drinks help you relax in the evening, then consider herbal teas and decaf tea or coffee.

    And if you need an energy boost, try green tea. On average, it contains ⅓ of the caffeine levels found in coffee.

    Finally, keep in mind that even though caffeine is a natural stimulant, there is no nutritional need for it in the human body.

    So if it suits you, you can choose to avoid caffeine completely.

    Maintaining a healthy, balanced lifestyle and diet will naturally boost your overall energy levels instead.

    There are both advantages and downsides to consuming caffeine on a daily basis. But millions of people still love coffee because they believe the advantages far outweigh the drawbacks.

    If that’s what you believe, then you must find the right coffee and equipment to meet your needs.

    Start your search with our comprehensive product reviews. Learn more about the different types of coffee that might work for you, or explore other aspects of caffeine with our caffeine guide.



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