Trouble Sleeping? Learn How Long Caffeine Stays in Your System


How long does caffeine stay in your system? What is the half-life of caffeine? How does caffeine half-life differ between individuals?

In this quick guide, we'll go over how long caffeine stays in the average person's body, what factors impact how long you'll feel the effects of caffeine, and what you can do to combat the caffeine jitters. Ultimately, we'll help you answer the key question: how long does caffeine stay in your body?


How Long Does Caffeine Stay in Your Body? The Average Person

Caffeine is absorbed by the membranes of your body incredibly quickly. Once you take in caffeine, you'll feel its full effects within 15-45 minutes. After that, your liver will start breaking down the caffeine into caffeine metabolites, which you will eventually excrete in urine.

In the average adult, the half-life of caffeine is about 5-6 hours. This means that once take a dose of caffeine, you'll break down about half of that caffeine after 5-6 hours. So if you take in 200 mg of caffeine at 9 am, you'll still have about 100 mg left in your body between 2 and 3 pm.


How Long Does Caffeine Affect You Specifically?

So now you know that the average person experiences a caffeine half-life of about 5-6 hours. But how long after drinking that cup of coffee or downing that Mountain Dew will you still be feeling a buzz? How long does caffeine stay in your body in particular? That depends on a few factors.


Your Unique Metabolism

Caffeine is processed and broken down by a set of enzymes in the liver. How much of that enzyme you produce is determined by genetics. This means that some people metabolize (or break down) caffeine extra-slowly, and some people break it down so quickly they barely feel the stimulating effects of caffeine.

The only way to really know how you metabolize caffeine is to have some and see what happens. If you are hypersensitive to caffeine, even small doses (think half a cup of coffee) may give you the "coffee jitters"—which can include feelings of anxiety, restlessness, nausea, diarrhea, heart palpitations, and general discomfort. If you are hyposensitive, you won't feel much of a stimulating effect from caffeine at a normal dose, even if you've never had it before.

Note also that pregnant women metabolize caffeine much more slowly, with an average caffeine half-life of up to eight hours.


Size of Caffeine Dose

Whatever caffeine half-life you have, the size of the dose you take will make a big difference in how long you still feel the impact of caffeine. If you drink one espresso shot (which has about 50-65 mg of caffeine) and your personal caffeine half-life is about five hours, you'll have a pretty negligible amount of caffeine in your system ten hours after ingestion. However, if you drink four eight-oz. cups of coffee in a row, taking in about 400 mg of caffeine, you'll still have 100 mg of caffeine in your system after 10 hours—enough to keep you pretty buzzed. Any amount of caffeine in your system about 50 mg may be enough for you to still feel some effects. (Or even less if you're hypersensitive!)

Note too that different products have different caffeine dosages. Coffee has more caffeine than black tea, which has more caffeine than green tea. Additionally, not all coffee brewing methods make equally strong coffee. For example, drip coffee has more caffeine than instant coffee. Even coffee from the same shop may have different caffeine content on different days!


Your Caffeine Tolerance

The more often you consume caffeine, the more tolerant you become to its effects. Regular coffee drinkers need to drink more and more coffee over time to get the same stimulating effects from caffeine that they did initially. If you're a new coffee drinker, expect to feel the impact of caffeine much more strongly than if you're a coffee veteran. (If you are a big coffee drinker, keep in mind that super-high caffeine doses are toxic. Try to moderate your intake so that you aren't constantly taking bigger and bigger doses.)


Other Drugs You Take

Other substances that you take into your body can impact how you metabolize caffeine and change the half-life of caffeine in your own body. For example, hormonal birth control can slow down how quickly you process caffeine, making you more sensitive to its effects. By contrast, regular smokers have a caffeine half-life of about three hours, making them less sensitive to the effects of caffeine.

Other drugs can also impact how you process caffeine, so look up how caffeine interacts with any prescription drugs or other substances you are taking.


Can You Speed Up the Half-Life of Caffeine?

Feeling the caffeine jitters? Are you anxious, panicked, or nauseated? Can you speed up your body's processing of caffeine to make yourself feel better?

In short, not really. There's not actually a reliable way to speed up the processing of caffeine in your liver in the short-term. However, here are some things you can do to help you feel better while you process the caffeine:


Drink Water

Drinking water won't "flush" your system of caffeine, in spite of the commonsense wisdom. However, caffeine is a diuretic, which means that it can cause dehydration. Drinking plenty of water will help minimize dehydration and help alleviate some of the symptomatic effects of the caffeine jitters.


Eat Food

Caffeine can suppress your appetite, so you may feel the impacts of low blood sugar, including nausea and headache, if you don't make a conscious effort to eat. Taking your caffeine with a meal will also slow down your processing of caffeine, which will make you less likely to have the jitters.



While exercise won't make you metabolize caffeine any faster, it will help you to burn off some of the extra energy caused by caffeine's adrenaline release. This may help you feel better.


Bottom Line: How Long Does Caffeine Stay in Your System?

How long does caffeine stay in the body? Well, the average person will experience the half-life of caffeine at about 5-6 hours. But how long does caffeine stay in the body such that you still feel its effects? This depends on a few factors:

  • Your unique metabolism: genetics plays a role in how fast your liver can metabolize caffeine.
  • Size of caffeine dose: A larger dose will impact your body for longer. The average person will feel some impact of caffeine at about 50 mg or above.
  • Your caffeine tolerance: The more often you take in caffeine, the less you'll feel its effects.
  • Other drugs you take: Other substances you take can speed up or slow down your caffeine metabolizing processes.

There's no way to actually process caffeine any faster in the short-term. But if you've had too much and you're uncomfortable, these things might help you feel better:

  • Drink water: Caffeine can dehydrate you, so water will make you feel better.
  • Eat food: Caffeine can suppress your appetite, so be sure to eat!
  • Exercise: Exercise can help you burn off some of the excess energy caused by taking caffeine.


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About the Author

Jane is a staff writer at PrepScholar.

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