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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  • James Quirk

    To be addicted to anything so as to make big companies rich seems like a no-brainer to be taboo for any of you… To make a product that is addicting for the purpose of addicting people to it so that you can sell to the addicts after you addict them seems like it should be ILLEGAL….. If you have to make a law so a dork puts a helmet on his head before he rids a bike, it shouldn’t be to big of a stretch to make it illegal to make children addicted to your product that is going to make you rich… Some people will do anything for a buck… You parents that allow your children to become addicted to this sh– should be —- I am not going to say what I am thinking….

  • giesthaus

    This might be a wake up call for some but companies are like mobs; they make money, they get political backing (and protection), they make more money. If you think you live in a free country then just try driving without your seat belt. Legislators are NOT acting in our (we the people) best interest, if they were then cigarettes would be as legal as cocaine. Seat belts are a great idea, but it makes for a very bad law. You will still be able to get a triple shot espresso at you favorite java vendor, you can smoke until your lungs dissolve… it’s legal. If I drive without my seatbelt I will be fined the equivalent of my weeks grocery budget… but I can still get a coupon for cheap or free cigarettes. It is all because given the opportunity, people will take advantage of people (most of the time). Welcome to the real world.

  • ethan

    i dont think the coffee companies are making that much money. iv never heard of a millionare ceo of a coffee company… and its coffee. addicted? the only withdrawel symptoms are headaches and nausia, i dont think its really that much of a problem.

  • Leon

    Ethan, the CEO of Starbucks has a net worth of over a billion American dollars and as a company Cost’s Coffee had an income of over 340 million pounds sterling for 2010/11. Coffee is big business, has potentially serious health risks and is addictive yet legislatively speaking isn’t in balance with other similarly unhealthy and addictive substances.

  • Falco Lombardi

    Seriously? People like coffee. I like coffee. Why would you make it illegal?

    People are capable of making their own decisions. Either way, making things illegal hasn’t ever eliminated a controlled substance…just makes it more expensive to acquire. Heroin is illegal, but somehow people still get it.

    Do you really want the government to control every aspect of your life?

  • First, you’re right about caffeine having a half-life of around 6 hours. If you consume 200 mg of caffeine, you’d still have 100 mg in you after 6 hours. Compromised liver function increases half-life by slowing metabolism. However, that 168-hour value is bullshit. The elimination kinetics of a drug in the plasma is determined by a process called feathering or curve stripping. When the plasma levels are measured with equipment that’s very precise, you sometimes get extremely long half-lives in spite of drug concentration being low enough to be clinically irrelevant.

    Excess caffeine consumption is dangerous, and the tolerance we build to it doesn’t help. I just wanted to clarify some pharmacokinetic details though.

    Finally, I like coffee a lot too. Can’t imagine giving it up!

  • Dan


  • Mandy

    I have had problems with caffeine addiction and I have spent more money than I would like to admit to on Starbuck’s chocolate covered espresso beans.

  • Luke Coombes

    I’m not sure about your country, but in mine (Australia) if you are involved in a car accident and you become a paraplegic because you were not wearing a seat belt, then you will be on a generous disability welfare package for the rest of your life. Similarly if you smoke 5 packs a day and get lung cancer agr 30 and do not have private health insurance (if you do there are still social costs involved in the form of increased premiums for everyone) your $100000+ chemo course of treatment will be paid for by the government. Now, it is evident that the social cost of taking these risks is very high and it not simply a case of risking your own life. Given the governments money is provided by hard working citizens and you are not going to be contributing anything as a life long paraplegic or during and for some time following your chemotherapy, you essentially are much more likely to become a social parasite if you take these risks….if you would prefer to risk your life every day go ahead and leave your developed country and move to India or Asia where you can smoke for next to nothing and not be weighed down by legislation that is put in place to preserve human life. Tell me which way of life you prefer at the end.

  • Tony

    Jesus, my ears are bleeding. Maybe layoff the coffee a bit?

  • Neo

    Hello. if half-life of caffeine in healthy adults is 5.7 hours then “full-life” is approximately 11 hours. does this then mean effect of caffeine could last 11 hours or does it only last until half-life? thanks.

  • Ted

    Hi Neo, It means that during the first 5.7 hours the effects of caffeine will be most effective. It will take 11 hours for the caffeine to be completely metabolized and eliminated from the body. Some of the effects of caffeine can last for at least 11 hours such as its interference with sound sleep. Please note that this can vary due to people’s sensitivity to caffeine.

  • snowted

    wrong. Half life means you will have half ofwhat your have taken aft period.For example. if you have 200mg after 5.7hrs you will have 100and after another 5.7 you will have 50mg and in another 5.7 you will have 25mg and so on.

  • snowted

    wrong see above

  • Ted

    He wasn’t referring to the amount of caffeine, but how half life relates to the perceived effects of caffeine in a person’s system over time.

  • snowted

    I was replying to your incorrect statement on halflife not his question.

  • Mark

    More likely that you will die if you don’t wear a seat belt rather than live with injuries if you do. And, the cost of health insurance is very high and so are taxes. I say, let “free” adults decide whether or not to take risks with their health.

  • Mark

    Common, with all due respect, let’s get real. Starbucks isn’t that successful because everyone is caffeine addicted. I drink coffee everyday, but I don’t go to Starbucks. I don’t like the taste of their coffee and I’m not the typical demographic of a Starbucks patron (you know, I don’t need to tell you; it’s more a social thing as anything else). I agree that laws should be made to protect one person or entity from causing harm to another (as in making harmful and addictive products illegal…and AS NOT IN something like the stupid seat belt law). But, things are indeed gray (most things are NOT black and white). Coffee is perhaps less harmful, even in a caffeine addicted person than candy is. So, should the government outlaw candy and fast food too? Common people. Yes, let’s get rid of cigarettes (gov’ts won’t because they get lots of taxes), but be smart about what to do away with. Just MHO!

  • Mark

    I agree, to a point. I think gov’t should create laws to protect one from another (not protect one from oneself). It is true that addictive substances reduce the power of the will and therefore it becomes less one’s choice and therefore the harm is more caused by the “pusher”. I’m all for laws that control drugs. I’d bet that there would be MUCH more drug addiction if drugs were made legal. That said, there are all degrees of harm and addiction. Heroin is much more addictive than caffeine and also much more harmful. If govt’s were to outlaw caffeine, perhaps they should also make table sugar illegal? Some people are addicted to Whoppers too. Should the gov’t close down Burger King? I think not. It is argued that caffeine and fast food can be consumed in moderation (I have a Whopper perhaps 3 times a year) without addiction or harm. Most people I know have a cup of coffee in the morning and are not suffering health issues as a result. Even those that I know that eat too much fast food and are overweight are not sick as a result. I know overweight people that lived into their 90’s. You get my point. Determine the real addictive and harmful products (cigarettes are probably high in the list by the way) and outlaw them. But, let people run their lives the way they see fit. Punish the pushers and help the addicts. Nuff said. Peace.

  • Martin You should totally go to Congo where they don’t tolerate that stuff.

Last Modified: August 28, 2016