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How Long Does Caffeine Stay In Your System? The Science of Coffee and Bedtime

Caffeine’s energy boosting effects are at their highest within the first few hours of consumption, but it can stay in your system for up to ten hours — so drinking coffee in the afternoon might mean a restless night ahead.

How Long Does Caffeine Stay In Your System? The Science of Coffee and Bedtime


Caffeine sensitivity varies from person to person, and drinking caffeine is not safe for everyone

Caffeine can stay in your bloodstream for up to 10 hours

Drinking too much caffeine can lead to symptoms like headaches, dehydration, and nausea 

Did you know?
People have been drinking caffeine since as early as 2737 BCE!

After that first sweet sip of morning coffee, it only takes about fifteen minutes for caffeine to enter your system and start waking you up. You might find yourself feeling extra alert and active during the following hours.

This feeling eventually wears off, and we all know coffee is no substitute for a good night’s sleep. But how long does caffeine keep you awake?

The answer will vary depending on how sensitive you are to caffeine, which can be influenced by your size and gender. Caffeine can stay in your system for up to ten hours, but the amount of energy it brings you will decrease throughout this time.

The Basics of Caffeine

A regular part of many of our day-to-day lives, caffeine can turn around a groggy morning or help speed along a late-night project. But it’s not a healthy choice for everyone.

According to the FDA, your average adult can safely drink around 400 mg of caffeine per day. This comes with a warning, though: not everyone responds to caffeine the same way!

A cup of coffee that leaves you feeling pleasantly refreshed might leave your friend feeling anxious and jittery.

It’s always a good idea to check with your doctor about how much caffeine you should personally be consuming. For some people, the safest amount of caffeine to drink is no caffeine at all.

Health problems like high blood pressure can make caffeine a poor choice, and it can be dangerous to combine caffeine with certain medications.

You may want to limit your caffeine intake if you have anxiety, struggle with a sensitive stomach, or generally have trouble sleeping.

what is caffine

What is Caffeine?

Caffeine is a stimulant that is found in many foods and drinks. It’s rapidly absorbed by our bodies and boosts energy by stimulating the central nervous system.

Caffeine is considered a drug and does have addictive qualities, but consuming moderate amounts is generally considered safe. That said, some people do develop caffeine dependency or addiction, so it’s a good idea to keep an eye on how much you’re relying on caffeine to get you through your days.

To understand how much caffeine you’re consuming, you’ll need to know what foods and drinks contain caffeine. Coffee, tea, chocolate, and some sodas contain caffeine, because caffeine is naturally present in coffee beans, tea leaves, cacao pods, and kola nuts.

Caffeinated energy drinks and medications typically contain synthetic caffeine, which is produced in pharmaceutical plants.

Though synthetic caffeine and natural caffeine come from different sources, studies have shown that they have the same effects as a stimulant. Whether synthetic or natural caffeine is the right fit for you comes down to your personal preference.

How much caffeine is in brewed coffee?

Your average 8 oz cup of coffee contains only 95 mg. But this number varies widely based on factors like what coffee beans are used and how the cup of coffee is brewed.

Espresso contains about five times as much caffeine as brewed coffee, which is why people usually drink espresso in much smaller amounts!

Espresso is the caffeinated base of many coffee drinks, so the caffeine content of lattes, cappuccinos, and Americanos all comes down to the amount — and strength — of espresso inside.

How much caffeine is in energy drinks?

Most energy drinks contain around 100-300 mg of caffeine per serving, so if you’re following serving size guidelines, energy drinks may not give you much more caffeine than your daily cup of coffee.

Since energy drinks typically contain synthetic caffeine, it’s always a good idea to check the label on the specific drink you’re considering.

How Long Does Caffeine Stay In Your System?

Technically, caffeine can stay in your body for as long as 10 hours. This number varies widely from person to person, since everyone’s body responds to caffeine differently.

Generally, our bodies absorb caffeine completely within an hour, and the energy-boosting effects stay at their peak for several hours.

While you might not be able to measure how long it takes until caffeine is completely out of your system, it’s a good idea to assume that as many as six hours after you consume it, half of the caffeine will still be in your bloodstream.

If you notice unpleasant side effects after drinking caffeine, this could be a sign that you’re particularly sensitive to it — especially if you feel them after just one coffee or soda. It could also be a sign that you’re simply drinking too much caffeine overall.

No matter how well you tolerate caffeine, it isn’t considered safe to drink more than 400mg a day. This is as much as four or five cups of coffee!

If you’re drinking more than this, you might find that you start to feel some of the common side effects of excess caffeine, such as anxiety, restlessness, and nausea.

When you drink too much caffeine it can also give you a headache, increase your heart rate, and make you dehydrated.

How Long Does 300mg of Caffeine Stay in Your System?

How Long Does 300mg of Caffeine Stay in Your System?

Even a moderate amount of caffeine like 300mg can stay in your system for 10+ hours, but many people will stop feeling the caffeine’s effects earlier than this. Caffeine has a half-life of five hours on average, so half of it will be out of your system after five hours, give or take.

How Do You Flush Caffeine Out of Your System?

It’s not possible to actually remove caffeine from your body or make your body process it faster, but staying hydrated can help reduce the side effects. Try to drink plenty of water and make sure you’re eating enough, too.

If you’re having trouble sleeping after drinking too much caffeine, you can also try to find natural sleep solutions such as weighted blankets, sleep masks, or aromatherapy.

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Caffeine During Pregnancy and Breastfeeding

Typically it’s considered safe for pregnant people to drink about one cup of coffee per day, but it’s always best to ask your doctor before drinking caffeine during pregnancy or while breastfeeding.

One recent study at the National Institutes of Health found that pregnant people who drink small amounts of caffeine may have smaller babies compared to pregnant people who didn’t drink any caffeine.

Since smaller babies tend to have more health risks, this could mean that it’s best to cut out caffeine entirely during pregnancy, but more research is needed in order to say for sure.

When it comes to breastfeeding, it’s a similar story: drinking a moderate amount of caffeine should be safe, but there isn’t enough evidence to guarantee just how much caffeine someone who’s breastfeeding can safely drink.

If you’re breastfeeding and drinking a moderate amount of caffeine, you’ll want to keep an eye out for signs that your baby could be reacting to the caffeine. If your baby is extra fussy or restless, it could be a sign that small amounts of caffeine are present in your breast milk.

Can you sleep with caffeine in your system?

Can you sleep with caffeine in your system?

According to the Sleep Foundation, it’s best to stop drinking caffeine at least eight hours before bedtime. This gives your body enough time to process the caffeine before you need to sleep.

It is possible to sleep after drinking caffeine, but it’s particularly hard if you’re within those first few hours when the caffeine’s effects are strongest. Instead of lying awake in bed, there are several steps you can take to relax when you can’t sleep because of caffeine.

Journaling and meditation can help to calm your body and mind into a sleepier state, and some people find that listening to white noise or soothing music lulls them off to sleep.

But sometimes, the best thing to do when you can’t sleep is to get out of bed. If you can’t fall asleep for more than twenty minutes, chances are you aren’t sleepy enough to doze off.

Getting out of bed can help remind your brain that your bed is a place for sleeping, not staying up feeling anxious and jittery.

Try to keep your mind busy with a non-stressful activity (like reading or listening to a podcast) and keep your light levels low. Once you feel sleepy again, you can return to bed.


Caffeine helps many people feel more energetic and productive during the day. Our bodies absorb caffeine within ten minutes, and its effects are strongest over the first few hours that follow. But drinking caffeine less than eight hours before bedtime can make it harder to fall asleep at night.

How long caffeine stays in your body varies widely from person to person, but in general, half of the caffeine you drink will be gone after six hours. After about ten hours, most of the caffeine will have left your system.

However caffeine tends to affect your energy levels, it’s not a good substitute for a restful night’s sleep. If you find that you’re having trouble waking up in the morning, you might want to reconsider your sleep hygiene habits before reaching for another cup of coffee.