How long does caffeine stay in your system?
Read this before you dive into your next caffeinated beverage.
Written by
Dan Cable
Medically reviewed by
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Last updated
March 19, 2024
min read
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Over 60 plant species worldwide contain caffeine; some — tea, coffee, and cacao — were central to traditional cultures and early global spice trades. Caffeine has since remained a central theme in globalisation, perhaps coming full circle with the rise of coffee in China, the homeplace of tea [1].

Caffeine is a stimulant with some particularly desirable effects, at reasonable doses, because it does not present the typical stimulant trade-off between promoting attention and eroding memory function. It also has some other benefits but in this article, we're focusing on how caffeine affects stimulation. 

So, before you dive into your next caffeinated beverage, read this.

How does caffeine stimulate the central nervous system?

Caffeine’s stimulation of the central nervous system (CNS) is largely mediated by:


Caffeine blocks adenosine receptors, stimulating adrenals (epinephrine, norepinephrine) and dopamine, each with further downstream CNS effects, to promote wakefulness.


Caffeine stimulates cortisol secretion, releasing stored energy (lipolysis, liver glycogen) but also triggering and accentuating agitation and mental stress and disrupting the natural daily cycle in melatonin/cortisol, which is critical for quality sleep [2].


Caffeine inhibits cAMP breakdown (increased energy) and stimulates renin, which vasoconstriction and blood pressure alongside the adrenals [3].

How long does caffeine stay in your system?

The half-life of caffeine is around 5 hours depending on your metabolism and genetic factors [4]. Half-life refers to the time it takes for the quantity to reduce by half its original amount.

For example, if you've consumed 10mg of caffeine, you'll still have around half of that, 5mg, in your body 5 hours later. This is why it's recommended to leave a good chunk of time between your caffeine consumption and bedtime.

While the short-term effects of caffeine are usually experienced within 5-30 minutes of consumption, some of these effects can last up to 12 hours in some people.

Caffeine is primarily processed by the liver into 3 metabolites each with interesting properties that are worth exploring further [5]. 

Paraxanthine (80%)

Higher-potency effect on adenosine antagonism and lipolysis but has lower toxicity, less anxiogenic effects, and a shorter half-life than caffeine — perhaps a more desirable profile than caffeine itself.

Theobromine (11%)

Vasodilator, thereby increasing oxygen and nutrient flow to the brain/muscles (noting that cacao/cocoa naturally contains theobromine).

Theophylline (4%)

Increases heart rate, blood pressure, and respiration rate but has the highest toxicity — perhaps a key driver of caffeine’s undesirable agitation [6].

Any stimulant in high doses, including caffeine, will induce agitation and anxiety, while also disrupting sleep duration and quality. Caffeine also affects GABA and serotonin levels in the brain so overall mood and performance implications should be considered [7][8].

How to optimise your caffeine intake

With all of this in mind, we should be mindful and when and how we drink caffeine and learn how to optimise our dosing.


Caffeine (like alcohol) has biphasic effects so dosage should be optimised for performance vs. agitation [9]. There are many inputs, including personal preference, to determine your optimal dose but it’s important to be mindful of tolerance.

How much caffeine is too much caffeine?

Well, the Australian Institute of Sport suggests 2-3mg of caffeine per kilogram — there’s 200mg in an espresso — for physical performance while others suggest no more than 300mg for cognitive performance [10][11].


Many now view mid-morning as the optimal time to consume caffeine to maximise the circadian rhythm at waking and avoid the adenosine slump later in the day [12].

However, caffeine has a long half-life so we must be mindful of avoiding post-midday coffees that will affect our natural melatonin cycle and impact sleep timing and quality. We all know that consuming caffeine late in the day can impact your sleep but it's worth the reminder.


Caffeine tolerance can quickly form within a month and so should be cycled to maximise the ergogenic benefits [13].

Just be mindful of withdrawal, which kicks in within 24-48 hours and can last as long as 9 days [14].


Caffeine stacks well with L-theanine (naturally present in tea), which moderates the agitation of anxiety effect without any major tradeoffs.

Other approaches that involve clearer trade-offs include nicotine with caffeine to gain performance synergies and accelerated caffeine metabolism, and caffeine with aspirin for increased performance, likely due to aspirin’s moderation of caffeine’s cerebral vasoconstrictor effect, however, there are risks, particularly in the elderly [15][16].

Caffeine alternatives

If you're looking for an alternative to drinking caffeine in the form of coffee and energy drinks, there are a few things you might like to try.


Found in Kucha tea, theacrine is a cognitive stimulant with a longer half-life but has little impact on heart rate [17]. This isn't yet well researched but watch this space.


Natural metabolites of fatty acids provide an immediate source of cognitive and physical energy and can be supplemented for performance gains [18].

Cold showers

Cold showers and ice baths stimulate your CNS and adrenals to provide more energy.

Caffeine may be a wonder drug, but it can easily become something you rely on to temporarily give you a boost. At Compound, we work with members to monitor caffeine intake while also providing coaching on appropriate dosing based on sleep quality, HRV, and other factors. 

Compound is a digital clinic for performance health, for men. Once the exclusive domain of billionaires and Hollywood stars, we're on a mission to make premium concierge care accessible to every man who wants more.

We are integrating diagnostics (bloodwork, scans, etc), treatment (medication, supplementation), performance programming, and support (coaching, accountability, care) — wrapped around a growth mindset.

Have you considered weaning off caffeine to experience what your energy and performance are like without caffeine's adverse effects? Get in touch today.

This post contains general information about health and wellness practices. It is not intended as medical advice and should not be treated as such. Please consult with a healthcare professional before starting any new health regimen. This information is provided without any representations or warranties, express or implied.

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