Hot coffee mug with beans spilled nearby

May, 23, 2023

How long does it take for caffeine to kick in?

Learn how long it takes for caffeine to kick in, how long its effects last, and how to consume caffeine responsibly, like using Ethan’s Natural Energy.

Many people can’t start their day without a cup of coffee, tea, or some type of caffeine. Caffeine is one of the most commonly used psychoactive substances, with about 80% of adults in the United States consuming some form of caffeine every single day. (1)

While caffeine can boost energy, increase alertness, and improve mental focus, it’s important to know the symptoms of caffeine and the potential long-term effects that consuming caffeine may have on the body. You may also want to know how long it takes to kick in, and how long the effects can last. 

Keep reading to learn all about how caffeine works and how you can optimize caffeine intake for maximum benefits.

How Caffeine Works

Caffeine is a stimulant that affects the central nervous system. It affects the brain and body by inhibiting the action of a neurotransmitter called adenosine, which normally decreases arousal and encourages sleep. Blocking the action of adenosine causes you to feel more alert and have better concentration. It can also make you feel less tired and drowsy. (2

Caffeine also causes the body to produce more adrenaline and dopamine, hormones that produce feelings of euphoria and pleasure. Caffeine is also known to increase heart rate and blood pressure, which may be beneficial for people who have low blood pressure. (2)

The body metabolizes caffeine in the liver by breaking down caffeine into smaller parts, which are then eliminated from the body through urine. 

Genetics, age, sex, and certain medications can alter the way caffeine is metabolized. Some people can have genetic variations that affect how quickly or slowly they metabolize caffeine, which changes how long it takes for caffeine to kick in and how long its effects last. 

Younger people and females metabolize caffeine more slowly than older individuals and males. Birth control pills and some antidepressants can also affect how quickly the body metabolizes caffeine. (3, 4, 5)

How Long Does It Take for Caffeine to Kick In?

There are a number of things that determine how long it takes for caffeine to kick in. Age, sex, hormones, weight, liver health, and food intake can affect the metabolism, absorption, and excretion of caffeine. (6)

What you’ve had to eat can also affect how long it takes for caffeine to kick in. Because caffeine from coffee, tea, and soda is absorbed quickly in the gut, the food you may have recently eaten, particularly fiber, can slow the rate at which blood levels of caffeine increase. So drinking caffeine on an empty stomach might give you an energy boost faster than if you drank it with your breakfast. (7)

The effects of caffeine can be felt as soon as 15 minutes after it is consumed. The amount of caffeine in the blood reaches its highest about one hour after consuming it and stays there for several hours in most people. 

Caffeine has a half-life of about 5 hours, which means that 5 hours after consuming caffeine, about half of it is still in your system. It can take up to 10 hours to rid your bloodstream of caffeine and for the effects to completely wear off. (8)

Over time, people can develop a caffeine tolerance when consumed regularly. This can decrease the energy-boosting effects and require a higher dose to be consumed to achieve the same stimulant effects. 

How long caffeine stays in your system?

The duration that caffeine remains in your system can vary depending on several factors. On average, caffeine has a half-life of about 3 to 5 hours. This means that it takes this amount of time for your body to eliminate half of the caffeine you consumed. However, it's important to note that caffeine can still have effects even after its half-life has passed.

In general, caffeine can stay in your system for several hours. It typically takes around 5 half-lives for caffeine to be fully metabolized and eliminated. This means that it can take up to 15 to 25 hours for caffeine to completely leave your system. However, individual differences, such as metabolism, liver function, and hydration levels, can influence how long it takes for caffeine to be cleared from your body.

Withdrawal symptoms

Withdrawal symptoms may occur when cutting caffeine out cold turkey. These symptoms, which include irritability, headache, agitation, depressed mood, and fatigue, are usually the worst within the first few days of cutting out caffeine. If you’re trying to reduce your caffeine intake, gradually decreasing the amount you consume each day can help prevent or lessen symptoms of withdrawal.

How to Optimize Caffeine Intake for Maximum Benefits

It’s easy to run on autopilot while you work and refill your coffee cup every break you get. What many people forget is that caffeine can become an addiction, even though it might be a seemingly harmless one. 

Caffeine is a powerful psychoactive substance, and consuming it intentionally instead of haphazardly can help you maximize its benefits.

Safe and effective dose

Be mindful of the amount of caffeine you consume. The U.S. Food and Drug Administration (FDA) says that 400 milligrams (mg) of caffeine is a safe amount of caffeine for healthy adults to consume daily. 

A cup of coffee has about 95 mg of caffeine, while an espresso shot has about 65 mg. Energy drinks can range from 170-300 mg of caffeine. While most energy shots usually provide about 200 mg of caffeine. 

“Chocolate also contains some caffeine, so you should consider it as part of your daily caffeine intake,” says Victoria Whittington, a registered dietitian at Camelback Nutrition and Wellness. 

Ethan’s Clean Energy shots contain 150 mg of caffeine from natural ingredients. “It’s just enough to give you a safe and effective energy boost without the unwanted jitters,” says Whittington. 

Timing of Caffeine Intake

The best time to consume caffeine will depend on the desired effect.

To increase energy and focus for a workout, consume a caffeinated beverage 45-60 mins before your workout to get its full effect. (9)

If your goal is to increase focus and concentration for a long day of work or studying, you can drink caffeine at the start of your day. Most people start to feel the effects of caffeine in about 15 minutes, so give yourself at least 15 minutes before you start your project. 

Whittington also says, “Drinking caffeine too close to bedtime can negatively affect your sleep.” One study found that drinking caffeine within 6 hours of bedtime decreased total sleep time by an hour. (10)

To prevent interference with sleep, stop drinking caffeine 8-10 hours before bedtime.

Factors That Affect Caffeine Absorption

Several factors can influence the absorption of caffeine in the body, ultimately affecting how quickly it takes effect. Some of the common deciding factors include:

Metabolism and individual differences

One crucial factor is an individual's metabolism. People with faster metabolisms tend to process caffeine more efficiently, leading to a quicker onset of its effects.

Body weight and composition

Factors such as body weight and composition play a role. Those with lower body weight may feel the effects of caffeine more intensely due to a higher concentration in their system.

Tolerance to caffeine

Regular consumers of caffeine may have developed a tolerance over time, requiring higher doses to experience the same effects. On the other hand, occasional consumers or those with low caffeine tolerance may feel the effects more strongly and rapidly.

Consumption on an empty stomach vs. with food

Whether caffeine is consumed on an empty stomach or with food can impact its absorption rate. Consuming caffeine on an empty stomach generally results in faster absorption, while having it with food can slow down the process.


There are several things that affect the way your body metabolizes and absorbs caffeine. This ultimately affects how long it takes for caffeine to kick in and how long it takes to leave your system. Most people will start to feel the effects of caffeine within 15 minutes of consuming it, however, it may take longer for some. 

Be sure to limit the amount of caffeine you consume, staying below the recommended 400 mg per day. With 150 mg of natural caffeine, Ethan’s Natural Energy Shots can help boost your energy levels, plus improve concentration and focus without consuming too much caffeine. 

You may also want to avoid drinking caffeine at least 10 hours before bedtime to prevent any negative effects on your sleep.


The effects of caffeine typically wear off within 3 to 5 hours after consumption.

Authored By

Kristen Carli

Kristen Carli is the owner of Camelback Nutrition & Wellness. She graduated from University of Arizona with a BA in psychology and then received a BS in dietetics from Arizona State University. After completion of the dietetic internship, she continued her education by receiving a MS in Human Nutrition from University of Western States. Having a passion for nutrition communication, she writes for many food and nutrition outlets as well as regularly develops recipes for food brands and media companies. Her nutrition expertise has been featured in InStyle, Bustle, Livestrong, The List, MyFitnessPal and many others. Additionally, Kristen is often featured via local TV segments sharing nutrition tips and tricks. She was selected to act as a Produce for Better Health Foundation Fruit and Vegetable Ambassador in Action, helping to promote the health benefits and importance of consuming fruits and vegetables, as well as a FoodMinds upwaRD winner for 2022, honoring up and coming media dietitians. You can find her reading, running, and exploring new restaurants with her husband and baby boy.

Read more

Keep Reading