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.

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  • Joe Carmical

    It would increase at an exponentially decreasing rate because the way a half life works is the more that you have in you the faster it gets consumed. Example: 1 cup of 200 mg coffee every day. Day 1 200mg intake, 6 hours later 100mg, 12 hours later 50mg, 18 hours later 25mg, 24 hours later 12.5mg+day 2 coffee=212.5mg, 6 hours later 106.75mg, 12 hours later 53.4mg, 18 hours later 26.2mg, 24 hours later 13.1mg+day 3 coffee= 213.1 path continues:
    Day 1: 200
    Day 2: 212.5
    Day 3: 213.28
    Day 4: 213.33
    Day 5: 213.333
    Day 6: 213.33332
    Day 7: 213.33333253
    Day 8: 213.33333328
    Day 9: 213.33333333

  • Donna Martin

    Joe, I am writing a paper, (regrettably due properly formatted Sun night at midnight MST.) Ironically, I will probably be consuming more than my share of caffeine today/tonight in an effort to stay up and focused to finish it! May I quote the stats you posted here? Sadly, since this was posted 4 months ago, you may not see this request in time.

  • kjdj

    no…he isn’t right…jeez. people on the internet spread misinformation like wildfire…http://www.mathcentre.ac.uk/resources/uploaded/half-lives.pdf

Last Modified: August 28, 2016