Caffeine has been a best friend of a lot of us in time of need. When we need help to keep our eyes open to cram those projects for work or school or when we need to function in that 5:00 am shift! Surely, none of us missed how caffeine can affect us, either good or bad. It is something so natural, so obvious that we tend to forget to question what is caffeine really?

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What Is a Caffeine

It can be found from either coffee, cacao, and tea extract or even synthetically; caffeine is a stimulant that affects your brain and central nervous system making you more alert and energetic. It is a type of drug that blocks your adenosine receptors, which prevents you from the inevitable sleepiness. One main reason why we get obsessed with premium coffee beans or roasted espresso beans covered with chocolate is this same ability. Even way back, caffeine is our easy fix to function in our daily lives.

Benefits of Caffeine

Alerting Agent or Cognitive Performance

Caffeine is infamous for boosting cognitive performance, mainly alertness and wakefulness to a lot of its consumers.  And when I say cognitive, this also involves improvements with reaction times, incidental verbal memory, and visuospatial reasoning! Unfortunately, you can also develop tolerance to caffeine, so it is still advised that you take them on an on-off basis. 

Burns Fat and Helps in Post-Exercise Recovery

Have you been waiting for an easy way to lose fat? This is good news for us since most of the recommended antioxidants and diets are offered in coffee or tea packages because it has caffeine. Caffeine tends to change our body’s metabolic substrate that causes an increase of lipolysis for fat burning. It also promotes glycogen resynthesis that helps you in exercise recovery.

Glycogen is essential to our body because it is our source of energy. Through caffeine, glycogen was substituted by fat; hence, we have energy reserves to function. And as we waste glycogen through exercise, caffeine will be the answer to get us until the end of the day! 

Helps Better Your Memory

This is also known for coffee drinkers that caffeine may boost long-term memory and reduce the risk of Parkinson’s and  Alzheimer’s disease. This is through the help of Phenylindanes that prevents two of your protein fragments that are common in both the disease from clumping hence stopping it for further development of the disease. Need some memory boost with that group presentation? Serve a homemade latte!

How Does Caffeine Work

Caffeine is absorbed quickly through the bloodstream once it is consumed. After that, it goes straight to the liver and will be broken down into simplified compounds and hence distributed to different organs to function. As a psychoactive drug, the center of caffeine’s function is mainly focused on the brain by blocking the adenosine receptors that will help you relax or be tired.

Basically, this blocking mechanism will help you stay alert and awake since it will prevent the adenosine from building up in your body throughout the day. This may also inflate your adrenaline levels as well as brain activity from dopamine and norepinephrine, which will further stimulate the brain for enhanced focus and concentration, making you ready to go no matter what once you finish tea time or finish a round of coffee; with the world’s best coffee mug!

Pros and Cons of Caffeine

Pros and Cons of Caffeine


  • Easily accessible and it is a natural drug. Unlike other vitamins or compounds where you need to go to your local pharmacy to gain access, caffeine can be found in our normal snacks and drinks such as coffee, tea, sodas, and even chocolates!
  • Keeps your brain healthy. Besides the fact that it improves your cognitive performance, caffeine also helps with long term memory retention and aids with Parkinson’s and Alzheimer’s disease.
  • May help you get in shape. It can burn fats since it helps you substitute them to glycogen as an alternative source of energy.
  • Energy booster. It helps you function by extending your energy and keeps you alert and awake!


  • Can definitely keep you up. Even if you don’t want to. Caffeine will disrupt your sleep if you take them at the wrong time or intake them too much. Hence delaying your body clock.
  • High doses of caffeine can cause side effects such as diarrhea, palpitation, nausea, and muscle tremors. It is advisable that before you drink one, use a tablespoon to measure how much coffee to scoop since that can contribute to overdose.
  • It is hard to stop consuming it. For coffee dependent people, withdrawals can occur from headaches, sleepiness to mood swings. Feeling so irritable lately after you have changed your diet? Coffee withdrawal can be the reason!

How Long Does It take for Coffee to Kick in

Coffee seeps into our bloodstream almost immediately; however, if you wanted to know how long it takes to be apparent, I would say around 30 to 60 minutes. This is a time where caffeine is at the peak level of your bloodstream. Caffeine has a half-life of 3 to 5 hours, meaning it would take that long for half of the dosage of it to be removed from your body. The other half, however, may remain in your body for quite a while.

Factors That Affect the Rate of a Caffeine Kick in

Caffeine Administration

Different ways of administration affect the speed of caffeine kick in for sure. Medicines that include them will kick faster since they are meant to react faster than food or drinks that require further digestion. Caffeine has almost 100% oral bioavailability; hence this is its primary route of administration. Through oral administration, caffeine kick happens in 45 to 60 minutes, lasting from 3 to 5 hrs. It can also be administered through a parenteral route, which is used with apnea treatments with premature newborn or post-dural puncture headaches. Another route is rectal, inhalation, and insufflation. Inhalation and insufflation are considered as misuse for caffeine. Caffeine was treated as a drug to make you high due to the high absorption rate, which is just a few minutes. However, even with a faster kick, the effect is shorter in comparison to others.


Our bodies react in different ways concerning caffeine. Genetically, a person can have a slow or fast metabolism with it. Slow caffeine metabolizers usually have a slow kick in, and unfortunately, can have potential caffeine build up in their bloodstream hence experiencing a longer effect. The liver  CYP1A2 gene’s key enzyme varies on each individual and significantly impacts a person’s caffeine metabolism. This is the one that will determine if you have a faster metabolism than another individual.

Caffeine Tolerance

Caffeine dependence is not a thing, even though coffee dependence is. The reason for this is that repeated or routinized intake of caffeine can cause caffeine tolerance and obviously, you can’t be dependent on a drug that doesn’t work its effect on you anymore. Caffeine tolerance is a continuous decrease of caffeine effects the more you have to consume it to the point that it doesn’t affect you anymore. It is an occurrence that a lot of frequent caffeine consumers are unaware of under the assumption that caffeine will still affect them even when they take it every day.

Concentration of Caffeine

This often gets confused with dosage since dosage has a certain concentration also. In simpler terms, caffeine concentration is the abundance of caffeine in one intake or substance. It is always important that we take caffeine in a controlled concentration since this can result in some risk, especially to people that are not used to consuming it. 


Factors That Affect the Rate of a Caffeine Kick in

As expected, age affects caffeine to kick in due to metabolism speed or caffeine clearance. The younger you are, the faster your caffeine metabolism is; hence you can easily remove caffeine from your system, but as you grow older, you have to readjust your timing since there’s a huge chance that it may affect your sleep if you drink it later on a day. There is even an experiment regarding metabolism vs age where it shows that you can have a whopping 30% difference in the rate of metabolism when you are younger versus when you are old! That sounds tragic since you really need to lay low on caffeine sooner or later!

Eating Food With Caffeine

Caffeine limits are highly dependent on your caffeine consumption in all aspects. This includes drugs, drinks, and yes, food.  Eating food with caffeine and consuming it in other means will affect the rate of reaction through dosage. Additionally, since food required more digestion than when it was taken in liquid form, caffeine kick in will be slower than usual.

Healthy Liver and Kidney

The liver and kidney play a key role in caffeine metabolism. The healthier your liver and kidneys are, the better your caffeine clearance, meaning it has a faster kick; however, it also leaves your body faster.

Drugs and Medication

Some medicines do include caffeine. Hence this is where overdosage or under dosage can play its role. Having the proper dosage of caffeine, including the medicine or drugs a person has consumed, will greatly affect its effect rate.


Surprisingly, smoking tends to encourage caffeine clearance.  Hence the halflife of caffeine, as well as metabolism, is expedited. Frequent tobacco users or smokers highly likely won’t benefit from drinking caffeine since it will stay in their system for only a short time.

Frequency of Drinking Coffee

Coffee drinking frequency is often associated with caffeine tolerance. The more you consume coffee every day as a habit, the larger the chance of coffee tolerance might occur; hence the rate of caffeine kick in may be faster than usual at first and will be slower in the long run!


Caffeine dosage usually targets specific effectiveness. Meaning, you consume a different dosage depending upon what you want to happen in your body; for example, if you have to battle obesity or if you have a headache or you want to improve your memory, there is a specific dosage of caffeine for that defining how many controlled milligrams and how often you have to take them (just like medicines!). In general, however, increased dosage equates to faster caffeine kick in. It is important to pinpoint, though, that overdosing caffeine is bad for you.

Factors That Speed Up Caffeine Kick in

Efficient Pharmacokinetics

Pharmacokinetics refers to the processing of the body of the drug that it had taken. This pertains to bioavailability, metabolism, absorption, distribution and excretion. Efficient pharmacokinetics helps with immediate caffeine kick in since it gives faster metabolism, absorption and distribution rate. However, this also means that it has a swift excretion rate hence the caffeine effect won’t last long in your body.

Immediate Action in CNS & PNS

Since Caffeine is a psychostimulant, it is obvious that one thing that affects its rate of a kick is the nervous system’s mechanism. The central nervous system (CNS), which involves the brain and spinal cord and the peripheral nervous system that includes all the other nervous system tissues, reacts through caffeine differently. Through PNS, caffeine effects are seen both in Somatic ( speed of activation of noradrenaline and serotonin neurons connected to release of local dopamine and methylxanthine action, respectively) and Autonomic nervous systems(rate of cerebral blood flow that may affect brain hypoperfusion). CNS, on the other hand, relates its speed through motor activity through adenosine receptor antagonism.

Placebo-Like Confound

 One of the things that show how the law of attraction is indeed a thing. Through thinking that caffeine is taken, our brain sometimes anticipates its effects to the point that the consumer thought they had already felt the caffeine kick even when it is not yet active. Through placebo confusion, caffeine kick seems to get faster than it normally should.

Co-Administered Substances

Caffeine tends to react well with other drugs.  Through caffeine, other drugs can elevate its effect with cocaine, aspirin, and the like. Caffeine influences drug absorption rate through enzyme inhibition, induced production of gastric acid, and increased gastric emptying rate, affecting drug degradation, conversion to other forms, or dissolution.

Factors That Slow Down Caffeine Kick in

Factors That Slow Down Caffeine Kick in

Abnormal Pharmacokinetics

When any of the pharmacokinetics factors are not in sync with each other, or if your metabolism is slower, you may not feel the caffeine kick immediately. However, this would also mean that you might feel its effect longer than it’s supposed to be; hence an unplanned sleepless night may happen!

Medical Conditions

Caffeine kick can also be affected by various medical conditions. Its effects can also be longer with patients with hepatic disease, infants, and even up to 100 hours for neonates! Pregnancy can also prolong the half-life and may cause miscarriage. As for smokers, it is believed that it can increase caffeine clearance.

Lack of CNS Adaptation

Let’s say when your central nervous system didn’t adapt properly to caffeine, there is a high likelihood you won’t feel the kick. Lack of adaptation is more like immunity with it even when it enters your body. Your CNS’s usual response with caffeine will not materialize; hence, the kick will either be slow or non-existent!

Why Caffeine Might Not Work

Inadequate Caffeine Dose

If there is such a thing as caffeine overdose, there is also the opposite of it. This is when the amount of caffeine you have is not enough for it to take its effect; hence, you won’t experience the benefits from it. On average, EFSA recommends 400mg of caffeine from all of its sources a day with 200mg in a single dose deemed safe. However, it is also important to note that 100mg in a single dose affects a person’s sleep latency, depending upon their intake. But if you take way less than the recommended amount, chances are, you won’t even feel the difference with or without it.

High Caffeine Tolerance

Caffeine tolerance develops due to intake of it regularly. Due to that habitual taking of caffeine, its effect usually disappears or lessens, for our body had already adjusted to it. No wonder you don’t feel wide awake anymore, even when you drink coffee at night!

Rapid Caffeine Metabolism

One of the current trends of caffeine lover classifications is your speed of metabolism.  Basically, it is categorized into two, which are the “slow” metabolizers and the “fast” metabolizers. Fast metabolizers are caffeine consumers who have a liver that processes caffeine fast enough to the point where you can hardly feel its effect or you can only experience the effect in a short period of time. So here, it wouldn’t matter if you follow the “How to make a bulletproof coffee guide” to the T and drink it; the caffeine will hardly affect you!

Do’s and Don’ts With Caffeine Intake


  • Do limit your caffeine intake to the recommended amount of caffeine by EFSA.
  • Do try to get to know your body. Caffeine reacts differently to each of us. It is important to know how it affects you personally.
  • Do know your teas and coffee. Read each label. Understandably, you have a specific preference in your snack and beverages; however, same as coffee types with distinct taste, each food and beverage contains varying amounts of caffeine. This is important to take note of if you are sensitive to caffeine.


  • Don’t take caffeine if you are pregnant, with high blood pressure, or with heart problems.
  • Don’t overdose on caffeine. Even if you really need to stay awake! 
  • Don’t drink or eat caffeinated food and beverages if it is already late at night. This can definitely affect your sleep patterns!
  • Don’t intake powdered pure caffeine! Other than the fact that the FDA and the American Academy of Sleep Medicine forbid it, it can negatively affect your health.

FAQ About Caffeine Intake

FAQ About Caffeine Intake

How long does caffeine stay in your system?

This can vary because metabolism can affect its speed. As I said, caffeine’s half-life is around 3 to 5 hours. The other half is completely dependent on your metabolism, food intake, and other factors.

Can caffeine not affect you?

It can! There are a lot of reasons why caffeine may not affect you. Genetically, we all have different kinds of adenosine receptors and some receptors may not bind well with caffeine; hence it doesn’t affect the person taking it. It can also be because of high tolerance, lack of dosage, and your fast metabolism. It won’t be surprising that despite intaking caffeine, you still feel sleepy!

Is caffeine bad for your heart?

Anything too much can be bad for a person’s health. Although caffeine had always been associated with the risk of coronary heart disease, most of the studies regarding this matter are conflicting. However, one of the additional effects of caffeine is palpitation or increased heart rate and also breathing rate, an occurrence that may be bad for the heart if it happens repeatedly.

Is caffeine more effective on an empty stomach?

There’s little to no evidence that caffeine intake with an empty stomach is more effective versus when it is full, the same as if it will increase acidity and indigestion. What is more important is knowing how your body reacts to caffeine since that would determine the drug’s effectiveness and side effects.

How can I drink coffee for maximum effect?

Maximizing the effect of caffeine can be done through various means. To get the benefits of coffee, specifically being awake and alert, it would take more than getting a brewer for coffee and an alarm clock! It involves strategies such as proper timing of when you are going to drink the coffee with respect to your cortisol level, amount of adenosine, and the half-life of caffeine. You must also note if you have been taking caffeine regularly and decreasing your intake to avoid caffeine tolerance and check if you have the right dose for you to feel the effects and benefits. 


Caffeine has many benefits and side effects depending upon how and when you have consumed it, the kind and dose you had taken, and your body reaction and genetics. So before you buy that blender that will grind your coffee with ease or that percolator so that your coffee can have a smoother texture and taste, make sure that you know yourself well to adjust your caffeine intake to harvest its advantages and avoid its negative side effects. After all, coffee doesn’t stay fresh for long.

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