The Half Life of Caffeine

half-life-of-caffeineHow long will caffeine be in my system?

Caffeine has become the hot-topic of the moment.  Its addition to so many products makes it important to know how long caffeine sticks around in the body in order to prevent possible overdose.

Caffeine takes a certain amount of time to work through your system. One study some years ago showed that the half-life of caffeine in healthy adults is 5.7 hours (see source). This means if you consume 200mg of caffeine at mid-day, you would still have 100mg in you at around 5.45pm.

What factors can delay caffeine’s half life?

The same study mentioned above showed that people with compromised liver function had a significantly longer half-life (a 49-year-old woman having alcoholic hepatic disease had a serum half-life of 168 hours).

Others can have genetic factors influencing the gene responsible for caffeine metabolism. The gene CYP1A2 is needed by the liver break down up to 95% of the caffeine in the body. Other genes can influence how well this gene does its job (src).

Some people may lack the gene or the gene may be defective. In this case, caffeine stays in the body a long time, increases sensitivity to caffeine, and can even cause allergy-like symptoms.

A variation of the gene PDSS2 also affects speed of metabolism. Those with the variation need a lot less caffeine to feel the stimulant affects.

Another study looked at how grapefruit juice may slow down caffeine metabolism in the liver, but it only was a slight inhibitor and wasn’t enough to cause warning.

What is the safe limit of caffeine in the body?

With caffeine levels in beverages and food continuing to climb – many people are asking – what exactly is the safe  limit?

While the average caffeine consumption is around 200mg per day, The Mayo Clinic recommends that people not exceed to 500-600mg per day. Consuming more than this can result in adverse overdose symtoms. This of course is affected by body weight, health, and individual sensitivity.

People can build up a tolerance to the effects of caffeine requiring larger doses to produce the same desired effect. If you are unsure of how much you can handle, it is best to start small and gradually increase your caffeine consumption as needed. Sometimes a caffeine detox is needed to reset caffeine tolerance back to safer/normal amounts.

Those who have built up a high caffeine tolerance can have severe caffeine withdrawal symptoms when detoxing, so it may be wise to quit caffeine gradually.

A lethal dose of caffeine (LD50) consumed orally is equivalent to 150 milligrams per kilogram of body weight, which is what we base our Death by Caffeine application on.

In conclusion, the half life of caffeine might be around 6 hours, but can be influenced by other factors. Caffeine is a drug and should be used with discretion as well as respected.

Get Help Quitting Caffeine

Reduce your caffeine intake without pain and discomfort.

See our new 10-step plan
  • Joe Garza

    Maybe right,maybe wrong! I drink coffee to sleep like a baby! and i do.:)
    Have been drinking it for atleast 55 years. So get you a cup!

  • Ted

    You are what we call an ultra-processor of caffeine. Unfortunately, the majority of the population are a lot more sensitive to caffeine.

  • Jeremiah

    right cause half life “halves” each time right? like if a half life is 6 hours to remove half of the caffeine, after the first half life then the second would remove half of the rest of caffeine, and so on, till it approaches ten half lives in which it’s generally accepted as being out of the system. just like carbon 14 dating, they count half lives of almost 6000 years, and after 10 half lives (60000 yrs) then the dating method is over, thus C14 is only viable for up to 60k years, ten half lives.

  • Mike Rights

    I’m going to go brew a pot of Love Buzz organic coffee, this article made me thirsty….and yes, it’s about 7pm.

  • Ogmudbone

    Am I the only one who snorts crushed up coffee beans

  • Pickel

    I like pickles

  • Og Adminbone

    Frida likes burritos

  • Larry

    If half life is 5.7 hours then at 11 hours, after initial dose of 200mg… you’ll be at about 50 mg of caffiene, then 25mg at about 17 hours, then 12.5 mg at about 23 hours… so-on and so-forth… it’s nothe completely metabolized at 11 hours, it only at a 1/4 of initial dose…

  • Styve

    This is so cute

  • Lalay sarip

    I often drink coffee because when I drink coffee I have difficulty in sleeping. I can’t sleep for two days and when I drink coffee during exam I buy melatonin or other sleep inducer in order for me to sleep.

  • Michael Liles

    It seems to be a bigger problem then you think as my girlfriend is sick all the time and im comming to thr conclusion that it maybe from caffeine. My sister died at 35 with heart issues couldn’t drink coffee but with a starbucks and d&d on every block for some (not all )its very hard to pass up this lethal drug.

  • Eric Burgess

    Are there any studies on caffeine and sleep apnea?

  • Ted
  • Daniel San

    I know this is old but I would bet many people find this in search still. Half life in reference to your body eliminating drugs or other chemicals is not the same as half life in radiation. It’s also a relative number based on a particular dosage and will vary by person. The example here is 200mg caffeine with an average of 5-6 hours half life. It simply means that at around 5-6 hours you’ll be at around 100mg still in the system. At 10-12 hours you should have eliminated most of that 200mg and be close to 0mg in system. Your body will scale up it’s elimination efforts at higher dosages but it’s not a linear scale. So for example you could probably ingest 400mg caffeine and probably still expect about 200mg to be in your system in 5-6 hours. There is a limit at which the kidneys can’t keep up though and you won’t be able to eliminate it as that scale.

  • m.flanegan

    Thanks Daniel, you’re right, i did just find this in a search – and did find the half-life discussion confusing. Your explanation was very helpful.

  • Faye Green

    I had a triple shot espresso cafe con leche around 5am (250mg), so at 11am it should be 125mg. Do I half it every 6 hours?
    If I do then by 5pm I should have 62.5mg and 11pm I should have 31.25mg.

    I rarely drink strong Cuban coffee, only when I get up late and have to rush out the door so I won’t be late for work.

  • Ted

    Yes, that’s correct in theory, but your personal genetics also plays a role in how fast caffeine metabolizes.

  • Faye Green

    Interesting. I didn’t take into account my genetics.
    Thanks for clearing that up

  • g

    Shouldn’t all recreational drugs be legal because we “like” it?

  • Dan Richter

    So if a person has a cup of coffee every day at the same time, because the half-life doesn’t have the caffeine completely removed yet, wouldn’t caffeine continue to build up in your system over time?

Last Modified: August 28, 2016