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Half Life of Caffeine – A Tale of Variables

Half-life – Caffeine metabolism is a fascinating topic, and that’s because it is so unique to the user. In our recent article ‘How to Have a Healthy Relationship with Caffeine’, we touched on the detoxification process, taking around 5 hours to clear approximately half of the total caffeine consumed, give or take. Today we are going to take a deeper look at this facet of caffeine in particular.

Half-Life is only Half the Story

Half-life? What does that mean?? Half-life is the average time it takes for half of the total item ingested to be cleared from our system. In this instance for example with caffeine, it would take around an average of 5 hours for the only 125mg of caffeine to be cleared from a 250mg serve. However, there are multiple things that alter how caffeine is metabolized in the body and these can include variables you may not have considered that can also increase this time or shorten it:

  • Alcohol. [3]
  • Smoking. [6]
  • Genetic Predisposition. [7]
  • Oral contraceptives. [1]
  • Poor or altered diet. [5]
  • Sleep. [8]
  • Medications. [1]
  • Disease states. [7]

For example, one study done on women taking oral contraceptives showed that the group of 9 healthy women taking oral contraceptives, showed a significant increase in the caffeine half-life from the non-contraceptive group of 6.2 hours to the OCP group taking 10.7 hours. This was just on a standard 250mg serve of caffeine too. [1]

Alcohol and Caffeine both require the Cytochrome p450 enzyme pathway, which is primarily found in the liver cells. Cytochrome P450 enzymes account for 70-80% of total drug metabolism in the body. [2]. Alcohol intake of around 50g per day significantly increases the half-life of caffeine by 72% and decreases clearance by around 36%. [3]

Diet Factors you Potentially Haven’t Considered?

If you are taking in flavonoids or consuming large amounts of them like that of quercetin – keep in mind that they can also alter the half life time frame, increasing its clearance time by around 32% which we found super interesting! [4]. Grapefruit too weirdly enough prolongs caffeine half-life by around 30%! [5]

What can you do to Sip Smarter?

  1. When taking into account the half-life and total time it takes to be processed by the body, a good way to work out a healthier way to get your caffeine in is to time it correctly around your sleep and wake cycles. Try to limit higher intakes later in the afternoons so that you aren’t staring into space in bed wondering “why am I like this!?”.
  2. Think about what dietary influences or medications you may be incorporating into your daily life that may impact these metabolic processes of clearance.
  3. Try not to stack too many coffees, I know, sounds easier said than done but caffeine is accumulative so if you are having a few in a 5-6-hour period you’re adding to that half-life period.
  4. Get a good night’s sleep, studies recently showed that if you are having caffeine even 6 hours before bed generally reduced total sleep had by around 1 hour [8]. If you pair your coffees/caffeine around your sleep and wake cycle properly, it shouldn’t really be something you need to depend on to wake up and instead can be something you enjoy getting a little buzz out of as you should.


  1. Patwardhan RV, Desmond PV, Johnson RF, Schenker S. Impaired elimination of caffeine by oral contraceptive steroids. J Lab Clin Med. 1980;95(4):603-608
  3. Willson C. (2018). The clinical toxicology of caffeine: A review and case study. Toxicology reports5, 1140–1152.
  4. Chen, Yao & Xiao, Peng & Ouyang, (2009). Simultaneous action of the flavonoid quercetin on cytochrome P450 (CYP) 1A2, CYP2A6, N-acetyltransferase, and xanthine oxidase activity in healthy volunteers. Clinical and experimental pharmacology & physiology. 36. 828-33. 10.1111/j.1440-1681.2009.05158.x.
  5. J. Clin. Pharmac. (1993), 35, 431-436
  6. Parsons WD, Neims AH. Effect of smoking on caffeine clearance. Clin Pharmacol Ther. 1978;24(1):40-45. DOI:10.1002/cpt197824140
  7. Wadhawan, M., & Anand, A. C. (2016). Coffee and Liver Disease. Journal of clinical and experimental hepatology6(1), 40–46.
  8. Caffeine Effects on Sleep Taken 0, 3, or 6 Hours before Going to Bed. Christopher Drake, Ph.D., F.A.A.S.M., Timothy Roehrs, Ph.D., F.A.A.S.M., John Shambroom, B.S., Thomas Roth, Ph.D. Published Online: November 15, 2013