Here's how long the effects of caffeine last

By Shannon Sweeney — / Coffee Talk

How long does caffeine last? 

When that first drop of caffeine hits our tired, miserable lips, we're instantly transformed. We become happier, full of energy, and know our coffee is going to get us through our day. But how long do these feelings last? 

The answer: Caffeine lasts in our systems anywhere from 4 to 6 hours on average, and it has a half life of about 5 hours. That means if you consume 200 mg of caffeine, after 5 hours, you'll still have 100 mg left in your body. It only takes about 45 minutes for 99 percent of the caffeine in our morning joe to be absorbed into our bloodstreams. 

A tattooed hand holding a mug of coffee.

Factors that contribute to how long caffeine lasts include: 

Once caffeine enters your body, it triggers the release of dopamine in your brain and puts you in a better mood, which is why it's considered a psychoactive drug. And the reason why caffeine keeps us alert and awake is because it blocks the sleep-inducing molecule adenosine in our brains. But coffee affects way more than just our brains—research has found it has an effect on our livers, our hearts, and more

It's important to note that caffeine effects each and every person differently—and it's scientifically known that humans have 3 levels of sensitivity to caffeine. This determines how well you metabolize caffeine and how it affects you in general.

Genes play an important role, too—those with a specific variation of the gene PDSS2 process caffeine more slowly than others. Therefore, they need less coffee for the same stimulant effects. 

At the end of those 4 to 6 hours, you may feel yourself experiencing the dreaded caffeine crash with symptoms of extreme tiredness, inability to concentrate, and irritability. But luckily there are many ways to prevent this from happening in the first place. 

Related: Here's what coffee does to your brain

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