How long does Caffeine Last in Coffee?

Have you ever brewed a cup of coffee in the morning, left it to cool down and returned hours later to find it still standing on the kitchen counter? While cursing your forgetfulness you may have asked yourself a common question. Is this coffee still ‘good’? Will it still give my nervous system a wake-up call or is it just an expensive glass of water? How long does caffeine last anyway?

Once dissolved in boiling water, caffeine doesn’t really lose its effects on the human body. Caffeine molecules do not break down in coffee. A cup of coffee will normally give you the same rush whether you drink it immediately or only after rediscovering it at the end of the day.

The simplest way to imagine it is to compare it with salt. If you mix a teaspoon of salt into a cup of water, the water will remain salty for as long as the salt remains dissolved. Caffeine works in much the same way.

How long does caffeine last in Coffee?

Coffee doesn’t tend to go bad as long as it’s kept dry and even then, the revitalising effect is only lost because it seeps out into the moisture. The caffeine itself really just moves around rather than disappearing or becoming inert. As long as you don’t pour the contents of the cup down the drain, you won’t be losing any caffeine.

Additionally, if you manage to wait long enough for the entire cup to evaporate, the leftover material will probably contain the same amount of caffeine that you started out with.

How does Caffeine work?


Caffeine in its most basic form is a bitter, white odourless powder. It does not lose its effect on the central nervous system regardless of its form. A coffee buzz can occur regardless of how it is consumed. Whether dry, brewed or however else you can imagine it, ingesting caffeine will always have the same effect.

How does Caffeine work?

Once consumed, coffee makes its way through the body in a similar way to most other liquids, meanwhile, the caffeine is separated and absorbed into the bloodstream. From the bloodstream, the chemical is processed by the liver before making its way across the blood-brain barrier.

When the caffeine reaches your brain, its tell-tale effects come into play. Once inside the brain, caffeine binds to certain receptors responsible for sleep.

The natural upshot of suppressing these ‘sleep receptors’ is an overly alert and reactive mind. This process is responsible for the extra attentiveness felt soon after drinking a warm (or cold) cup of joe.

The time it takes a person to begin feeling their cherished coffee buzz is a result of many variables, suffice to say, the exact time will always be dependent on the individual but most people will start to feel it after between 30 minutes to an hour.

How long does caffeine remain in your system?

That’s a harder question to answer. Dana Hunnes, Ph.D, a senior dietician at UCLA medical centre points out that the average half-life of caffeine inside the body is between 4-6 hours. 

But doesn’t half-life refer to radioactivity? Actually, the half-life of anything is just the time it takes to halve its original total. When it comes to caffeine, it’s very difficult to say when it will be totally and completely out of your system, for that reason, it’s more accurate to measure when most of it will be out and when most of its effects will have disappeared. And for most of us, this will take about 4-6 hours.

Effects of Caffeine

As mentioned above, caffeine’s most notable effect is an increased level of alertness coupled with a decrease in fatigue. Unfortunately, the body’s reactions don’t stop there. A sharp uptick in your caffeine consumption can also result in:

Effects of Caffeine
  • Increased blood pressure and heart rate – When you experience a heightened level of alertness your heart beats faster to compensate. Whether you’re being charged by a lion or drinking one too many espressos, a more alert body will result in a more alert heart.
  • Mood Swings/Irritability – Everyone has experienced stress at some point in their life, and almost everyone has reflected on their regrettable cattiness during the ordeal. If you’re always drinking coffee, you’ll always be in a state of tepid fright which will lead to many unfortunate and curt responses.
  • Headaches/general withdrawal symptoms – As with any addiction, after a certain period of time, the body may become dependent on the substance and you may feel a host of unpleasant side effects as your body attempts to cope with a sudden scarcity.

Once again, the effects of caffeine are varied based on the individual taking it and as such, other, unlisted symptoms may occur.

Can I build up a tolerance to caffeine?

As caffeine intake increases in both volume and frequency, most individuals will begin to experience a certain tolerance to its effects.

But how does this work? Well, as caffeine flows into the brain and inhibits the receptors responsible for feelings of fatigue and tiredness, the body compensates by activating more receptors. More receptors mean more caffeine is required to dull their effects, thus the more caffeine you ingest, the more you’ll eventually need to really affect your body.

How long does caffeine last in Coffee?

Is Caffeine only found in coffee?

All this information may make you want to dial back your caffeine intake but sadly, it’s not that easy. Caffeine is not just found in coffee (although that is generally where it is found in its highest numbers). You can also expect to find caffeine in many other foodstuffs which may spike your intake if you’re not careful. The most common sources are:

ProductVolumeCaffeine
Coffee250ml100-200mg
Tea250ml25-50mg
Soft Drinks250-350ml40-60mg
Sports Drinks500ml100-300mg
Flavoured Waters300-500ml50-100mg
Chocolate100g20mg
Sweets/Candies100g0mg
Beer250ml0mg
Is Caffeine only found in coffee?

In Conclusion – What is caffeine and how long does it last in coffee?

Caffeine is a stimulant that increases alertness, reflexes and inhibits sleep and fatigue. It is found in many foodstuffs but is most abundant in coffee, caffeinated drinks and chocolate.

Caffeine does not lose its psychoactive qualities over time and retains these qualities even when dissolved, heated or mixed with other chemicals. With this in mind, a product high in caffeine will have various physiological effects on the individual who consumes it regardless of its age or current form.

The effects felt by a said individual will differ vastly depending on many factors ranging from weight and physique to the amount of caffeine consumed. Perhaps the most influential variable is the average caffeine consumption of the individual as a high, frequent intake will mute most effects.

Simply put, your coffee will always have the same level of caffeine present in it and the same rejuvenating effect will always be felt regardless of when you have it. If you aren’t feeling your usual coffee buzz, it may mean that your body is getting used to the caffeine and more will be needed to achieve the same result.

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