Center for Young Women's Health




  • Caffeine is considered a drug. Having too much caffeine can make you feel nervous or jittery.
  • The effects of caffeine can last up to 6 hours.
  • If you think you're having too much caffeine, the best way to cut back is to do it slowly.

Does it seem like everyone is walking around carrying a cup of coffee or an energy drink these days? People usually like the way these drinks taste, but many say they drink them for the caffeine boost. You may not realize that the side effects of caffeine may out-weigh the benefit of feeling more alert. Too much caffeine can make you feel “jittery” and nervous. It can also make your blood pressure and heart rate go up. This guide was created to help you learn about caffeine so you can make healthy choices about your caffeine intake.


What is caffeine?

Caffeine is naturally found in the leaves, beans, seeds, and fruits of many plants. It's also added to some foods and drinks and some pain relievers such as headache medicine. Caffeine is considered a drug. It works by exciting your nervous system which may make you feel more awake and alert. Having too much caffeine isn't healthy, and caffeine can be addictive. Although caffeine isn't stored in our bodies, the effects can be felt for up to 6 hours.


What are some sources of caffeine?

Common sources of caffeine include coffee, tea, some soft drinks, energy drinks, chocolate, some over the counter medicines, and some prescription medications. Teens usually get caffeine by drinking soda and energy drinks. Sodas such as Pepsi®, Coca-Cola®, Sunkist®, and Mountain Dew® and popular energy drinks such as Redbull®, Full Throttle®, and Monster® contain caffeine. Some companies such as Pepsi® and Coca-Cola® also make soda that doesn't have caffeine in it. Look for the word(s) “decaffeinated” or “caffeine free” on the can or bottle. Sprite® and Fresca® are two types of soda that do not contain any caffeine.


How much should I have?

The amount of caffeine that is safe for teens to have in a day has not been determined, but a moderate amount of caffeine (300 milligrams or less per day) is considered safe for adults. Teens who are having more than 300 milligrams a day should try to cut down on the amount of caffeine they are having.


What are the side effects with caffeine?

The effect caffeine has on a person depends on how sensitive that person is to it. Sensitivity is affected by body weight, the amount of caffeine a person has, and how often they have it. Some teens who are more sensitive to caffeine will feel stronger effects with smaller amounts than others who are less sensitive to it.


Having too much caffeine can cause side effects like “the jitters”, restlessness, anxiety, insomnia (trouble sleeping), headaches, high blood pressure and a fast heart rate. Caffeine is a diuretic, which means that it will make you have to urinate (pee) more often. It can be dehydrating if you are in the heat or working out because unlike sports drinks (such as Gatorade®), caffeinated drinks do not replace the water and minerals that you lose when you sweat. If you have caffeine in combination with some medications used for ADHD, asthma, and certain heart conditions, the side effects (such as feeling like you have the jitters) can be more noticeable and uncomfortable. It is important that you ask your health care provider if you should avoid caffeine.


How can I lower the amount of caffeine I have every day?

If you think you are having too much caffeine and would like to stop, the best way to do so is to cut back slowly. Stopping too fast can lead to headaches, fatigue or lack of energy, and irritability or crankiness for a few days.


The amount of caffeine you take in can be lowered by having “caffeine-free” or “decaffeinated” foods and drinks instead of the caffeinated ones. Cutting back on the amount of caffeine you are having may make you feel tired at first, but your energy levels will return to normal in a few days.


The following table lists how much caffeine is in some popular drinks and chocolate products.

*For coffee and tea products, the actual caffeine content can vary depending on the brewing method, the type of plant and the brand.

Source: U.S. Food and Drug Administration and National Soft Drink Association


Typical Milligrams of Caffeine
Brewed, drip method
(8fl. oz. cup)
Brewed, percolator
(8fl. oz. cup)
(8fl. oz. cup)
(1fl. oz. serving)
Decaffeinated, brewed
(8fl. oz. cup)


Typical Milligrams of Caffeine
Black tea bag (8fl. oz. cup) 50
Iced tea (8fl. oz. glass) 25


Typical Milligrams of Caffeine
Coca-Cola® (12fl. oz.) 35
Pepsi® (12fl. oz.) 38
Sunkist® (12fl. oz.) 41
Mountain Dew® (12fl. oz.) 54


Energy Drinks
Typical Milligrams of Caffeine
Red Bull® (8fl. oz.) 80
Monster® (8fl. oz.) 80
Full Throttle® (8fl. oz.) 80


Chocolate Product
Typical Milligrams of Caffeine
Milk Chocolate (1 oz.)
Dark Chocolate (1 oz.) 13
Chocolate Milk (8fl. oz.) 5
Chocolate Syrup (2 tb.) 2


Although caffeine may give you an energy boost, it might cause you to feel irritable and more tired when it wears off. It's important to think about the positive and negative effects of caffeine and talk to your health care provider to make sure it is safe for you to have caffeine-containing drinks, foods, and medications.


Written and reviewed by the CYWH Staff at Boston Children's Hospital


Updated: 6/14/2012


Related Guides:

Energy Drinks

The amount of caffeine in an 8-ounce can of an energy drink is about the same as that contained in 5 ounces of coffee - about half of a small cup of coffee. If you have too much caffeine, you may experience side effects, such as dizziness, nervousness, insomnia (trouble sleeping), upset stomach, or arrhythmia (irregular heartbeat)...

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