Caffeine is great when you need an energy boost in the morning, but it can easily affect your sleep come nighttime. The frustrating thing about caffeine though, is that it affects us all differently.
For some, they can have a latte after lunch and still be sleeping soundly by 9 p.m., whereas others need to be much more careful about when and how much caffeine they have each day. That’s because we all metabolize caffeine at different rates, so there’s no single answer to the question of how long caffeine lasts.
If you’re trying to make sure caffeine doesn’t impact your sleep, you’re much better off working out your ideal cutoff time — that is, the final time in the day you can have a coffee, or anything else with caffeine in, for it not to impact your sleep.
Below, we’ll cover how long caffeine usually lasts, but more importantly, we’ll dive into how you can find the ideal cutoff time for you each day, based on your own biology.
First up, how exactly does caffeine work and why can it impact our sleep so much?
When we ingest caffeine, enzymes in your liver break it down, metabolizing it into paraxanthine and theophylline. These compounds temporarily block the A1 and A2 adenosine receptors in the brain.
Adenosine naturally builds in your system the longer you’re awake, making you feel sleepy over time. But if this adenosine can’t bind to your receptors — because paraxanthine and theophylline are there instead — you won’t feel this sleepiness.
Instead, you’ll feel more awake. Caffeine doesn’t just block adenosine, though. It also triggers the release of adrenaline, giving you a mental and physical energy boost. It makes us feel more alert and increases attention, reaction times, and even memory.
Your body absorbs caffeine quickly, too. It reaches peak levels in your system 15 to 120 minutes after you consume it, so you start feeling the effects of caffeine fast.
Caffeine content all depends on the type of coffee beans or tea leaves, how it’s made, and the size of the serving. But here’s the typical caffeine levels in common foods and drinks:
But caffeine can come with side effects. High doses of caffeine can cause insomnia, and drinking too much of it can cause caffeine tolerance, meaning your body gets used to it and you need to have more of it to feel the same stimulating effects.
Plus, your body can become dependent on it and you may experience caffeine withdrawal. Symptoms of this include headaches, fatigue, irritability, muscle pain, and anxiety. We cover how long caffeine withdrawal symptoms last here.
Caffeine can easily disrupt sleep as it can delay when you fall asleep, reduce total sleep time, and decrease the amount of deep sleep you get.
It can also mask the effects of being sleep deprived, temporarily improving your performance and making you feel less sleepy. While this may sound like a great quick fix for a sleepless night, it can easily lead to caffeine dependence, which can impact sleep further, leading you to need more caffeine the next day. This vicious cycle leads to more caffeine and even more sleep loss.
According to sleep researchers Dieter Riemann and Christoph Nissen in The Oxford Handbook of Sleep and Sleep Disorders, a single dose of caffeine has a half-life of three to seven hours. This means it takes three to seven hours for the amount of caffeine in your system to decrease by half. Caffeine’s half-life can be longer if you have more of it, too.
So, for example, if caffeine’s half-life is five hours for you, and you had a cup of coffee at 12 p.m., you’d still have half of the caffeine in your system by 5 p.m., and a quarter of it by 10 p.m.
One study found 100 mg of caffeine at bedtime reduced slow-wave activity, also known as deep sleep. But this same effect on sleep was found when participants drank 200 mg of caffeine — about what you’d find in two cups of coffee — more than 12 hours before sleep. So, it’s clear caffeine lasts for a long time in our bodies.
A study published in the Journal of Clinical Sleep Medicine looked at participants who had 400 mg of caffeine zero, three, or six hours before bed to compare the differences. The results showed each of these caffeine times disrupted sleep, including those who had caffeine six hours before bed — their sleep time reduced by more than one hour compared to those who had taken a placebo.
Our genetics play a key part in how long caffeine lasts. For example, if you find caffeine doesn’t affect you much, you may not have very “sticky” adenosine receptors for caffeine to bind to. Our genetics also dictate how efficient the enzymes in our livers are at breaking down caffeine. If they’re less efficient, caffeine will take longer to be cleared from your system.
But it’s not all genetics. Factors like your age — usually the older you are, the slower you metabolize caffeine — weight, if you’re taking any medication, and even how long you slept for the previous night can all affect how long it takes your body to break down caffeine.
How long you feel caffeine’s effects can even change from person to person depending on lifestyle factors. For example, caffeine’s half-life is reduced by about half in smokers and doubled in women taking oral contraceptives.
So, the only real way to find out how long caffeine lasts in your body is to get a genetic test to look for factors that show you metabolize it faster or slower, and take into account other lifestyle factors.
However, if you’re trying to find out how long caffeine lasts so you can make sure it doesn’t disturb your sleep, there is a much easier, quicker, and cheaper way than getting a genetic test — and that’s finding out your caffeine cutoff time.
If you’re having trouble sleeping and think your afternoon caffeinated beverage habit may be to blame, you should figure out your caffeine cutoff time. Your caffeine cutoff time is the time of day you should have your last coffee — or anything else containing caffeine — to make sure it’s out of your system by bedtime. The timing of this cutoff is different for everyone, and it can even change for you each day.
That’s because your cutoff time is based on your circadian rhythm, the roughly 24-hour cycle that dictates when you feel awake and sleepy. The timing of this cycle is different depending on your chronotype — whether you’re an early bird, night owl, or something in between — and it can change each day depending on things like your meal, exercise, and sleep times, as well as things like light exposure.
When thinking about caffeine, your Melatonin Window is the most important part of your circadian rhythm. In the RISE app, this is a roughly one-hour window when your brain will be making the most of the sleep hormone melatonin it will all night. Go to bed during this time window, and you’ll have a much easier time falling and staying asleep.
But if you’ve had too much caffeine too late in the day, your adenosine receptors will be blocked, meaning you won’t feel the sleepiness effect. Instead, you’ll feel awake and alert, despite it being your ideal biological bedtime.
However, the adenosine in your body carries on building up as long as you’re awake, so when the caffeine is finally cleared from your system, you’ll be hit with a wave of tiredness and crash, especially if you’re sleep deprived. When this happens during the day, you feel the strong urge to grab another coffee just to keep functioning.
The RISE app predicts your circadian rhythm and Melatonin Window for you based on things like your inferred light exposure and sleep times. Then, 10 hours before your Melatonin Window each day, the app will show you your ideal caffeine cutoff time. You can see this on the Energy screen and even set reminders, so you don’t forget when you should be having your last coffee for the day. Plus, you can adjust this timing if you find you’re more or less sensitive to caffeine.
Most people’s cutoff time will be around noon. For night owls, this may be a little later, at around 2 p.m. Either way, many of us regularly consume caffeine after this, making it harder to fall asleep and get the right amount of sleep for us each night.
Caffeine can easily affect your sleep, but that doesn’t mean you need to give it up altogether. Caffeine is great at helping you overcome sleep inertia — that groggy feeling you get right after waking up — as well as giving you a boost of energy when you need it, if taken at the right time.
Here’s how to enjoy caffeine responsibly:
Use RISE to work out your caffeine cutoff time each day. Watch out though, this can change each day depending on how long you slept for the night before.
Aim to keep caffeine to earlier in your day, and set a reminder to warn you when you should have your last coffee, tea, or soda for the day.
Caffeine isn’t just in coffee. Tea (even green tea), soft drinks, energy drinks, kola nuts, yerba mate, and chocolate all contain it, too. So, think twice before you reach for dark chocolate for dessert or green tea as part of your bedtime routine. Even decaffeinated coffee contains caffeine, just in smaller amounts.
The half-life of caffeine increases if you have more of it in your system. The number is different for everyone, of course, but the Food and Drug Administration (FDA) has said to keep caffeine consumption to about 400 milligrams per day.
Those who are more sensitive may want to have less caffeine than this, and those with insomnia may want to avoid it altogether.
Too late in the day for coffee, but still need a pick-me-up? Or perhaps you’re cutting down on caffeine — or cutting it out altogether? There are ways you can get a boost of energy without caffeine.
We’ve covered more caffeine-free ways you can wake yourself up here.
Once caffeine is in your system, it’s hard to force your body to clear it faster.
If you’re lying awake in bed because of too much caffeine, you can:
We’ve covered other things you can do to make yourself tired here.
If you’ve had one too many coffees and find yourself with the jitters during the day, these things could help reduce this particularly unpleasant side effect:
Caffeine can last for 12 hours in your system, but it all depends on your genetics, age, lifestyle, and how much caffeine you have each day. The only way to really find out is by getting a genetic test.
But, if you want to make sure caffeine doesn’t affect your sleep, the easiest way to do so is by finding out your caffeine cutoff time. The RISE app helps you do just that.
The app calculates when exactly you should have your last coffee — or other caffeine-containing foods and drinks — based on your circadian rhythm each day. This way, you can still enjoy caffeine and give your body enough time to break it down before bedtime, ensuring it doesn’t get in the way of a good night’s sleep.
The half-life of caffeine can be anywhere from three to seven hours. So, if you drink 200 mg of caffeine, you’d still have 100 mg in your system about five hours later, and a quarter of it about 10 hours later. It can take up to 12 hours for caffeine to fully leave your system.
The amount of time it takes for coffee to wear off all depends on how much you’ve had, your genetics, and lifestyle factors. The half-life of caffeine is three to seven hours, so it can take 10 to 12 hours to fully leave your system.
Caffeine increases your blood pressure and heart rate within about 15 minutes to an hour of consuming it, and this effect can last for three to six hours.
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