Key Facts
  • Having too much caffeine may 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, you may want to cut back slowly
  • Esta guía en Español
  • Young men's version of this guide


Caffeine is a naturally occurring chemical found in the leaves, beans, seeds, and fruits of many different plants. It’s also added to some foods, drinks, supplements, and pain relievers. Caffeine is also called a central nervous system stimulant because it works by exciting your nervous system to help you feel more awake and alert. Having too much caffeine may make some individuals feel nervous, restless, or jittery. Too much caffeine can also make it challenging to fall asleep since the effects can be felt for up to 6 hours.

What are some sources of caffeine?

Common sources of caffeine include coffee, tea, caffeinated soda, energy drinks, chocolate, some over-the-counter medicines, and some prescription medications. Caffeine is also found in some dietary supplements, diet pills, energy shots, pre-workout supplements, and caffeine pills.

An energy drink is just like drinking coffee or soda, right?

Not necessarily. Most energy drinks have high levels of caffeine in addition to other added vitamins, minerals, and/or chemicals that could have an impact on the effect of the caffeine as well as your overall health.

How much caffeine should I have each day?

It’s recommended by medical professionals that those under the age of 12 not consume any caffeine, and teens limit or avoid caffeine, in part because the amount of caffeine that’s safe for teens to have in a day has not yet been determined. For adults, 400 milligrams of caffeine per day (which roughly equals 4 cups of coffee, 2 cans of soda, or 2 “energy shot” drinks, however, this can vary widely) is considered safe. Given that we do not yet know the amount of caffeine that is safe for teens, if you are drinking more than 400mg of caffeine (the amount in 4 cups of coffee or two cans of soda), you may want to consider cutting back.

What are the side effects of caffeine?

The effect caffeine has varies from person to person, depending on how sensitive someone is to the effects of caffeine. Sensitivity is affected by body size and typical intake of caffeine. Some teens will feel stronger effects with smaller quantities than others who may be less sensitive to it or who have gotten used to having it regularly.

Having too much caffeine can cause side effects like “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 than other beverages. It can be dehydrating if you are in the heat or working out, so for individuals sensitive to caffeine, it may be best to avoid it before vigorous exercise.

Another impact of caffeine that is particularly important for adolescents is its relationship to bone health. It has been reported that individuals who consume high amounts of caffeine may have bones with less density, ultimately leading to weaker bones. This happens because caffeinated beverages may interfere with your body’s ability to absorb calcium, a mineral necessary for bone development.

Caffeine can also cause certain medical conditions, such as heart problems, to worsen. Although it is uncommon, extremely high intakes of caffeine from energy drinks has been linked to some deaths in teenagers. If you consume caffeine in combination with some medications used for ADHD, asthma, and some heart conditions, the side effects (such as feeling like you have the jitters) can be more noticeable and uncomfortable. It’s important that you ask your health care provider if you should avoid caffeine if you have any medical conditions or while on certain medications.

In addition, caffeine can be especially harmful when mixed with alcohol. This is because caffeine can give a person who has been drinking a false sense of alertness.  This may make the typical effects of alcohol feel different, which can be confusing for the brain. It is very important not to mix alcohol and caffeinated beverages.

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

If you think you’re having too much caffeine and would like to stop, you may want to try and cut back slowly. Stopping too fast can lead to headaches, fatigue, lack of energy, irritability, or crankiness for a few days.

The amount of caffeine you consume can be lowered by having “caffeine-free” or “decaffeinated” foods and drinks instead of 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 within 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.

Coffee: Typical Milligrams of Caffeine:
Brewed, drip method
(8fl. oz. cup)
(1fl. oz. serving)
(8fl. oz. cup)
Decaffeinated, brewed
(8fl. oz. cup)
Tea: Typical Milligrams of Caffeine:
Black tea bag (8fl. oz. cup) 45
Iced tea (8fl. oz. glass) 47
Soda: Typical Milligrams of Caffeine:
Coca-Cola® (12fl. oz.) 34
Pepsi® (12fl. oz.) 39
Mountain Dew® (12fl. oz.) 55
Energy Drinks: Typical Milligrams of Caffeine:
Monster® (8fl. oz.) 160
Full Throttle® (8fl. oz.) 136
Red Bull® (8fl. oz.) 160
Rockstar® (8fl. oz.) 160
Chocolate Product: Typical Milligrams of Caffeine:
Dark Chocolate (1 oz.) 12
Milk Chocolate (1 oz.) 6
Chocolate Milk (8fl. oz.) 5
Although caffeine may give you an energy boost, it’s important to think about both the positive and negative effects of caffeine. Be sure to talk to your health care provider to make sure it’s safe for you to have caffeine-containing drinks, foods, and medications.