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​​​​​​Many people don't know that caffeine is a drug. It's a stimulant that's found in coffee, tea, energy drinks, some pain medicines, as well as in foods and drink. ​

Products with caffeine

Some common products with caffeine amounts are:

  • coffee (250 mL or 1 cup): 40 to 180 mg
  • decaf (250 mL or 1 cup): 2 to 5 mg
  • tea (250 mL or 1 cup): 10 to 110 mg

Other products that have caffeine include:

  • caffeine stimulants (1 tablet): 100 to 250 mg
  • energy shots or drinks (60 to 360mL): 4 to 240 mg
  • some painkillers (1 tablet): 30 to 100 mg
  • cola drinks (355 mL or 12 oz.): 30 to 60 mg
  • dark chocolate (56 g or 2 oz.): 40 to 70 mg
  • milk chocolate (56 g or 2 oz.): 3 to 20 mg
  • snacks with caffeine (for example, gum, fruit chews, jelly beans): 30 to 50 mg

Medical use

Caffeine can be used to treat some types of headaches, including migraines. Some pain medicines have caffeine. Your doctor or pharmacist can tell you if caffeine might work for you.

Short-term effects

Less than 200 mg of caffeine (1 or 2 cups of coffee) can make you more alert, put you in a better mood, and make you feel less tired. It can also improve physical work and thinking. The effects usually start within half an hour and can last up to 12 hours.

Some people are sensitive to caffeine, and even small amounts can make them feel sick.

Small amounts of caffeine might make your blood pressure go up, increase your heart rate, and make you pee more. If you have caffeine close to bedtime, you may have trouble falling asleep, sleep for a shorter time, or not sleep as deeply.

Larger amounts of caffeine (600 mg or more) can:

  • cause shaking
  • cause trouble sleeping
  • make you agitated
  • cause a fast, irregular heartbeat (heart racing)
  • make your blood pressure go up and then drop to very low levels
  • make you feel irritable, restless, and nervous

​Caffeine and health problems

People with anxiety disorders or heart problems shouldn't use large amounts of caffeine because it can make their condition worse.

It's rare for adults to die from having very large amounts of caffeine (overdose). People born with heart problems have died from drinking large amounts of energy drinks that contain caffeine and herbal stimulants.

Long-term effects

Most healthy adults that use low to moderate amounts of caffeine (up to 3 cups of coffee) every day don't seem to have any long-term effects.​​

Regular use of more than 600 mg of caffeine a day might cause long-term effects such as sleep problems, thinning of bones and fractures, more anxiety, and stomach acidity. It can also increase blood pressure, and if you already have high blood pressure, it can get worse.

Pregnancy and breastfeeding

More than 300 mg of caffeine (about 2 to 3 cups of coffee) in a day may be linked to miscarriages and low-birth weight in babies.

Caffeine is passed​ through breastmilk, which might make your baby irritable or have trouble sleeping.

If you're pregnant or breastfeeding you may want to limit or not have any caffeine.​

Caffeine and alcohol

Caffeine doesn't help you sober up if you drink too much alcohol.

Mixing caffeine and alcohol puts you at higher risk of drinking and driving or getting into a vehicle with someone who has been drinking. You might not realize the person has had too much alcohol, and the caffeine or energy drink might mask the drowsiness from alcohol.

You might also drink more than normal if you combine alcohol and caffeine (such as mixing alcohol with an energy drink). The more alcohol you drink, the higher the risk that you may pass out or have an alcohol-related injury. ​​

Caffeine and young people

Some products with caffeine, such as some energy drinks, have higher than the recommended doses of caffeine for children and teens. Because children and teens weigh less than adults, even a low amount of caffeine may harm them.

Children who drink pop or energy drinks with caffeine ​may feel restless, have behaviour problems, be irritable, have trouble sleeping, or wet the bed. Children can get very sick from even small amounts of caffeine.

Some teens who use a lot of caffeine may have health problems such as an increased or abnormal heart rate and chest pain. If this happens, they may have to go to the hospital or need an ambulance.

College and university students might use lots of caffeinated products (such as coffee, energy drinks, caffeine pills) to stay awake and study longer.

Lack of sleep and stress from school might make the effects of caffeine worse. It's important to find healthy ways to manage stress and get enough sleep.​

Tolerance and dependence

As your body gets used to caffeine, you need more and more of it to get the same effect (tolerance). As the amount of caffeine you have goes up so does the risk of side effects.

You can become mildly dependent on caffeine from drinking 350 mg (about 2 to 4 cups of coffee) a day. You might feel like you can’t function without it, or that you aren’t fully awake until you’ve had caffeine.


If you suddenly stop drinking caffeine, you might have withdrawal symptoms such as:

  • headaches
  • problems sleeping
  • feeling irritable, tired, and depressed
  • lack of energy
  • feeling down
  • having trouble focusing or concentrating

Withdrawal symptoms begin 12 to 24 hours after you stop caffeine. Most symptoms go away within a few days.​


If you're concerned about your or someone else's caffeine use, or you want to learn more about substance use, call the Addiction and Mental Health Helpline, any time of the day or night, at 1-866-332-2322 (Alberta only).​​

Current as of: June 1, 2023

Author: Poison & Drug Information Service, Alberta Health Services