How Long Does It Take For Caffeine To "Kick In"?

How much caffeine is in a caffeine pill?

Each Vivarin pill contains 200mg of caffeine.

Come to think of it, that’s around twice as much as you would get in a regular cup of Joe, or 2.5 times as much as you would get in an 8.4 ounce Red Bull.


The bad about caffeine pills vs energy drinks

Spoiler alert – the energy boost from caffeine pills was a disappointment compared to energy drinks.

If you’re wondering about the effects and whether or not caffeine pills actually work, then feel free to skip ahead to further down the page.

The list of “inactive ingredients” in Vivarin caffeine pills is pretty scary once you start doing a little digging into what each of the ingredients actually does. Several of them have been linked to cancer, something that I’m not terribly keen to acquire.

Lastly, there’s no denying that an energy drink is just a more enjoyable experience and clearly tastes much better than simply downing a pill with a few ounces of water.

If you haven’t found an energy drink that you think tastes good yet, then you need to keep looking because they are definitely out there.

How long does it take for caffeine to work for me?

After drinking green tea, coffee, or an energy drink – I’ll usually notice caffeine “kicking in” or taking effect within 15 to 20 minutes of ingestion.  The effect will be more substantial if I drink my caffeinated beverage quickly – as opposed to slowly sipping over a long period of time (such as while writing).

If I eat a large meal prior to drinking caffeine, it may take slightly more time for me to notice an effect – than if ingested on an empty stomach.  This is probably due to the fact that a large meal prior to caffeine consumption delays absorption and extends the time needed for caffeine to peak in the plasma.

Of all the times in my life that I’ve ingested caffeine, the only time I didn’t notice caffeine “kicking in” rapidly was when I administered a caffeine capsule.  I’m not exactly sure about the caffeine capsule formatting (e.g. delayed release, extended-release, etc.) – but it didn’t take effect for at least 45 minutes after ingestion.

That said, it’s possible that this capsule could’ve interacted with another supplement that I administered that day – possibly delaying its onset.  In any regard, my experience is consistent with the literature such that caffeine tends to take effect rapidly after ingestion of a caffeinated beverage, but slower with the administration of a caffeine capsule.

Moreover, I should mention that my genetic data indicate that I’m a rapid caffeine metabolizer (due to expressing the “A/A” genotype of rs762551).  I also should note that I have generally high anxiety and self-awareness, and carry a variant of the ADORA2A gene that’s associated with caffeine-induced anxiety – all of which may enable me to easily detect caffeine’s onset of action.

Symptoms of Overdose

The physical symptoms of caffeine overdose include agitation, hypertension (high blood pressure), hypotension (low blood pressure), vomiting, abdominal pain, and fever. The heart rhythm is often affected, with arrhythmias – disorders of the heart rate (pulse) or heart rhythm – including tachycardia, when the heart beats too fast.

Although cardiac arrest – the abrupt cessation of normal circulation of the blood due to failure of the heart to contract effectively – is possible from caffeine overdose, this is rare.

However, anxiety about rapid heartbeat is a common cause of panic attacks, which unfortunately tend to also cause a rapid heartbeat, of which the sufferer is acutely aware.

Therefore, don’t assume that you are having a cardiac arrest if you feel you have a racing heartbeat after consuming a lot of coffee! Nonetheless, the DSM-IV does define the criteria for caffeine intoxication much lower than that of caffeine overdose – after the consumption of just 250mg caffeine – about 2-3 cups of brewed coffee. There is some indication in the research literature that caffeine overdose combined with SSRIs can cause serotonin syndrome.

Caffeine: Everything You’ve Been Afraid to Ask

How to Take Caffeine Pills Safely

Follow the instructions on your caffeine pill label or ask your doctor for recommendations on how to take caffeine pills.

Follow these guidelines:

  • Limit your caffeine intake to 400 mg of caffeine per day. Remember that foods or drinks with caffeine, like coffee, tea, soda, caffeine drinks, and chocolate milk, have added caffeine. It may be best to avoid them when you take caffeine pills.
  • Avoid caffeine pills close to a time when you’re trying to sleep.
  • Avoid over-the-counter medications like cold or allergy medications unless you talk to your doctor first.
  • Avoid grapefruit juice when you take caffeine pills because it may increase the effects.
  • Watch for signs of overdose, like a fast heartbeat, nervousness, irritability, and trouble sleeping.

Do Caffeine Pills Work?

Like coffee and other caffeinated drinks, caffeine pills help you stay alert. If you’re tired or drowsy, they can help you feel more awake.

Why caffeine should “kick in” rapidly (Reasons)

  1. Efficient pharmacokinetics: Research suggests that, in most humans, approximately 99% of caffeine is absorbed within 45 minutes of administration. Plasma concentrations will peak within 15 and 120 minutes following oral ingestion.  The variance in time to attain peak plasma concentrations is related to: gastric emptying rate and dietary intake.  Following absorption, caffeine: reversibly binds to plasma proteins; is distributed within intracellular tissue water; and crosses the blood-brain-barrier to exert a psychoactive effect.
  2. Immediate action in CNS & PNS: The onset of caffeine’s action is relatively rapid for most people. Once caffeine is distributed throughout the peripheral and central nervous system, it modulates: adenosine receptor activation; sympathetic nervous system activation; hormone production; neural connectivity; the activation of brain regions; neuroelectrical activity (i.e. brain waves); and cerebral blood flow.  Due to the culmination of aforestated effects, most people notice caffeine taking effect quickly after administration.
  3. Placebo-like confound: Although caffeine is a potent psychoactive substance that usually takes effect quickly after administration, we must consider that a placebo-like effect may partly (or fully) account for rapid responses to caffeine. Having a strong expectation or belief that caffeine will “kick in” rapidly – may alter neurophysiology in ways that would be consistent with a placebo-like effect.  Neurophysiologic alterations from a placebo-like effect may synergize with the actual effects of caffeine to induce a quicker onset of caffeine action and/or more noticeable reaction.
  4. Co-administered substances: If you’re using medications and/or supplements with caffeine, there’s a chance that these agents might slightly expedite the rate at which caffeine “kicks in” – and/or the rate at which you’re able to perceive caffeine “kicking in.” For example, if you’re already under the influence of a stimulant, you might have an easier time noticing when caffeine takes effect due to the fact that the stimulants increase focus and self-awareness.

Related Posts

Caffeine Tolerance

Some people get a significant boost from one small, weak cup of coffee, while others need much more to feel any spike in alertness. Plus, caffeine has side effects, and the dose that comfortably wakes one person up in the morning could be far too much for another person, inducing anxiety and jitters.

Not only does the amount of caffeine in a cup of coffee vary from cup to cup but people each have their own caffeine tolerance level, which will increase as you increase the quantity you consume over time.

Plus, even if you drink the same coffee day after day, the amount of caffeine in it can change. That's because of natural variations in the coffee beans themselves, plus any differences in how those beans were roasted, ground, and brewed.

Read on for details on approximately how much caffeine is in a cup of coffee. Plus, we review how caffeine might affect you.

Verywell / Emily Roberts

What should you do if you have caffeine side effects?

High doses of caffeine can cause chills, agitation, dizziness, headache, vomiting, nausea, fainting, indigestion, lightheadedness, and seizures, according to the Mayo Clinic. You should check with your doctor immediately if any of these symptoms occur. You should get emergency help immediately if you show signs of overdose, which include irritability, nervousness, rapid heartbeat, and trouble sleeping. Other side effects, like a rash or dry skin, can occur but do not require medical attention.

What if it’s just a case of caffeine jitters? For minor caffeine ingestion, supportive measures, like drinking water and talking a walk, can help, Link suggests. More severe cases may require intravenous hydration or medications to treat irregular heart rhythm, for example. In life-threatening situations, dialysis may be the best option.

Caffeine Guide for Beginners

When used responsibly, caffeine can be an incredibly beneficial substance to use as it stimulates both the mind and body with only moderate side-effects for most people.

You’re going to start by first looking at what caffeine is and how it may be of benefit to you, before moving on up to our 2017 list of the best caffeine pills on the market this year.

Side effects

Given that it is so potent, it should not be surprising that caffeine has some side effect when taken in excess. According to the Mayo Clinic, taking too much caffeine (defined as over about 400 mg per day) can lead to headaches, nausea, insomnia, restlessness, tremors, and a rapid heartbeat (9).

Extremely high doses have even been associated with fatal overdoses. When taking caffeine pills, it’s important to know where the other sources of caffeine in your diet are.

If you already are taking a weight loss supplement, for example, you might be getting a substantial dose of caffeine as it is. Caffeine’s effects take several hours to wear off, so spread out the caffeine you do consume throughout the day.

Who Can Benefit From Caffeine, How, Why?

Any of you who are looking to increase your productivity could stand to benefit from using a caffeine supplement.

If you have a large work project coming up or perhaps an intense leg workout then caffeine will almost certainly become your best friend.

If you are currently dieting on low calories, and especially low-are, then you may find caffeine to be particularly useful for keeping your energy levels up when fatigue begins to set in.

We all know how hard it can be to work full-time while dieting and training hard, so adding a few hundred milligrams of extra caffeine into the mix can make a world of difference in terms of enabling you to function like regular human being despite being carb depleted.

In fact, anecdotal evidence tends to suggest that caffeine is even more effective in the absence of carbohydrates, so those of you using a ketogenic diet could enjoy even greater stimulatory effects from some of the products we are going to look at below.

See also: Top 10 Fat Burners for Men

2. How do you know how much caffeine a food or beverage contains?

Many packaged foods, including beverages and dietary supplements containing caffeine, voluntarily provide information on the label as to how much caffeine they contain. Consumers should take care when consuming for the first time a new packaged food containing added caffeine if the amount of caffeine in the food is not declared on the label.

There are several online databases that provide estimates of caffeine content of certain foods and beverages such as coffee and tea. However, the amount in these brewed beverages can vary depending on such factors as how and where the coffee beans and tea leaves were grown and processed and how the beverage product is prepared.

For reference, a 12 ounce can of a caffeinated soft drink typically contains 30 to 40 milligrams of caffeine, an 8-ounce cup of green or black tea 30-50 milligrams, and an 8-ounce cup of coffee closer to 80 to 100 milligrams. Caffeine in energy drinks can range from 40-250 mg per 8 fluid ounces.

Health Risks

Although the caffeine in coffee is usually safe in moderate amounts, there are people with certain health conditions who may benefit from limiting or eliminating caffeine consumption. Those health conditions include:

  • Pregnancy:The American College of Obstetricians and Gynecologists (ACOG) recommends limiting caffeine to less than 200mg daily during pregnancy.
  • Sleep disorders: Caffeine is known to worsen sleep and it is generally recommended that people who struggle with sleep limit or avoid caffeine—though consumption early in the day may be OK for some.
  • Migraine:Caffeine may trigger or worsen migraines, although research is unclear.
  • Anxiety: Caffeine can compound anxious feelings.
  • Gastroesophageal reflux disease (GERD):Caffeine may worsen symptoms of gastroesophageal reflux disease.
  • Glaucoma:Drinking beverages with caffeine may exacerbate higher eye pressure.

If you have any of these conditions, you should talk to your doctor about whether you should drink caffeinated coffee or other caffeinated beverages.

There are a few prescription medicines that interact negatively with caffeine, so you may need to avoid caffeinated coffee (and other caffeinated beverages) if you're taking one of these drugs, which include:

  • Certain anti-seizure drugs
  • Certain medications for asthma
  • Some antibiotics
  • Some antidepressants and other drugs used to treat mental health conditions
  • Thyroid medications

If you've been prescribed a drug that might fall into one of these groups and you have questions about your caffeine intake, make sure to discuss the issue with your pharmacist or physician.


Q: Are caffeine pills bad?

A: Caffeine pills get a bad rap because it’s quite easy to overdo it: the relatively long delay (60-90 minutes) between taking a pill and experiencing its full effect, and the high dosage per pill that’s common in many over the counter caffeine pills, makes it easy to blow past the optimal dose and get jitters and anxiety.

Caffeine does have some serious negative side effects if you take it in extremely large doses, but when taken at moderate doses it’s both well-tolerated and remarkably effective.

Many of the physical, cognitive, and fat-burning effects that people strive to get through complicated combinations of herbal compounds could be much more easily garnered with a 150 or 200 mg dose of caffeine.

So, caffeine pills are only bad if you don’t use them intelligently. At the right dose, caffeine is a very effective and versatile supplement.

Q: How long does a caffeine pill last?

A: You can expect the greatest effects of caffeine to last for a few hours. It takes an hour or so for a caffeine pill to achieve maximum effect, and by five or six hours, the effective dosage has dropped in half (this time duration is called the elimination half life).

One important thing to note about the effects of caffeine, and its elimination half life, is that it can be much longer (sometimes doubling the half life to ten or twelve hours) in women who are taking birth control pills, due to an obscure interaction.

This doesn’t have any real consequences in terms of caffeine’s efficacy; it just means that caffeine will last a lot longer in your system in this case, so you’ll have to be more thoughtful about when, if at all, to take another caffeine pill.

Q: What do caffeine pills do to your body?

A: Caffeine is a potent stimulant that modulates your body’s central nervous system, which accounts for its broad-reaching physical and mental effects.

Boosting athletic performance and cognitive performance at the same time is very hard to do unless you act on the central nervous system, which is exactly what caffeine pills do.

Additionally, caffeine also ramps up your body’s cellular metabolism, which boosts your baseline energy expenditure (and accounts for the thermogenic, weight-loss friendly effects of caffeine pills).

Q: Do caffeine pills help you lose weight?

A: Caffeine is a well-known thermogenic compound, so yes, caffeine can help you lose weight by increasing your body’s baseline caloric expenditure.

The effect is dose-dependent, with higher doses of caffeine burning more calories, but you do need to balance this with the negative side effects of caffeine at higher dosages.

Caffeine pills, or calorie-free caffeinated drinks like coffee and tea, are particularly effective ways to achieve the thermogenic effect of caffeine because you incur no additional energy intake (versus, say, a soda or energy drink, where the calories due to the sugar might offset any benefit in thermogenesis).

Q: Are caffeine pills good for studying?

A: Yes, one of caffeine’s most well-researched aspects is its nootropic potential: caffeine boosts cognitive performance, attention, and memory, particularly when you are sleep deprived.

The effect is so strong that the military has awarded specific contracts for companies to develop caffeinated products for military ration kits, so caffeine is a good tool to improve your studying, especially late at night.

Of course, you do need to be mindful of the fact that you won’t sleep well after taking a caffeine pill to stay up late, and sleep is very important for solidifying what you’ve learned during a study session.

So, caffeine is great for cognitive performance right now, but you do need to ease off the caffeine and sleep if you want to retain and recall information later.

Q: Should you take caffeine pills or drink coffee?

A: Caffeine pills are great if you need a fast, transportable, and easy way to boost your body’s caffeine levels. Coffee can deliver caffeine too, but it takes slightly longer to kick in.

Plus, the caffeine content of coffee varies from roast to roast. However, coffee contains compounds like chlorogenic acid that modulate the effects of caffeine in your body, and coffee is rich in many antioxidants that you will not get in a caffeine pill.

If you want short-term performance benefits (physical or mental), caffeine pills have the edge compared to coffee. However, if your goal is long term health, you should opt for coffee instead.

Q: How long does it take for caffeine pills to kick in?

A: Caffeine levels in the blood reach a peak about 60 to 90 minutes after ingesting a caffeine pill. The rise in blood caffeine levels will be slower if you take caffeine pills with a large meal, but aside from this, caffeine pills are quite reliable in their timing, which is one of their prime advantages—you know exactly what you will get.

Q: How many caffeine pills can you take?

A: Caffeine’s side effects ramp up at higher dosages, and fortunately, you don’t need a crazy high dose of caffeine to get optimal thermogenic and performance benefits.

Typically about three mg of caffeine per kilogram of body weight is the sweet spot for optimal benefits and minimal side effects; this translates into about 200 to 300 mg for most people.

Serious side effects don’t appear until much higher doses (some scientific studies have used up to nine mg per kg of body mass) but there is really no need to strive for an excessive dose.

Q: How are caffeine pills made?

A: Caffeine pills are usually made by purifying the caffeine that’s extracted from decaf coffee during the decaffeination process.

A solvent, usually water or supercritical carbon dioxide, is used to pull the caffeine out of the coffee beans. The beans then become decaf coffee, and of course the caffeine is left over and can be purified and packaged into caffeine pills.

It’s also possible to synthesize caffeine, but given the amount of decaf coffee that’s made every year, coffee beans are a more common source.

The pure caffeine powder is then pressed into tablets or pushed into capsules, along with binders and stabilizers (hopefully not too many).

Q: When should you take caffeine pills?

A: The optimal timing for taking a caffeine pill is about an hour or so before you need to perform at your best. You should also keep in mind the “come-down” from caffeine; given that caffeine (obviously) inhibits your ability to sleep, you should also time your caffeine pill dose so that it doesn’t keep you up super late, unless that’s what you want.

You’ll get maximum performance benefits from caffeine for a few hours, so you have some flexibility with when you take caffeine pills.

For weight loss, in contrast, you want to maintain a moderate level of caffeine throughout the day, so it’s best to take a caffeine pill early in the day, then let the long elimination half life of caffeine sustain your body’s caffeine levels throughout the day.

Even ten to twelve hours after taking 200 mg of caffeine, you’ll still have an effective dose of 50 mg in your body.

9. How can I cut back on caffeine without causing unpleasant side effects?

If you’re used to drinking caffeine-containing beverages every day, and want to cut back, it’s best to do so gradually. Stopping abruptly can cause withdrawal symptoms such as headaches, anxiety, and nervousness. Unlike opioid or alcohol withdrawal, caffeine withdrawal is not considered dangerous, but it can be unpleasant. You may want to talk to your health care provider about how to cut back.


Leave a Reply

Your email address will not be published.