For most healthy adults, an occasional energy drink is unlikely to cause harm, but they’re not a good everyday habit, and they’re not suitable for children, teenagers, pregnant or breastfeeding women, or people with heart problems. The two main concerns are caffeine and sugar. A small 250 ml can usually contains around 80 mg of caffeine, similar to a mug of coffee, while larger cans can contain 160 mg or more. Regular energy drinks contain about 10 g of sugar per 100 ml, according to USDA FoodData Central, so one 250 ml can provides about 26 g, nearly a whole day’s limit for adults. The European Food Safety Authority considers up to 400 mg of caffeine a day safe for healthy adults, and single doses up to 200 mg.
What’s in an energy drink?
| Ingredient | Typical amount | Notes |
|---|---|---|
| Caffeine | 30 to 35 mg per 100 ml in many brands; about 80 mg in a 250 ml can, 160 mg or more in a 500 ml can | The main active ingredient |
| Sugar | About 10 to 11 g per 100 ml in regular versions | Zero-sugar versions use sweeteners |
| Taurine | Often around 1,000 mg per can | An amino acid; no clear evidence it boosts energy |
| B vitamins | Often several times daily needs | Most people already get enough from food |
| Guarana, ginseng, other herbs | Varies | Guarana is another source of caffeine |
| Acids and colorings | Varies | Acidic drinks can harm tooth enamel |
Check the label: amounts vary widely between brands and can sizes.
How much caffeine is safe?
| Group | Suggested maximum |
|---|---|
| Healthy adults | Up to 400 mg a day, no more than 200 mg at one time |
| Pregnant or breastfeeding women | Up to 200 mg a day |
| Children and teenagers | Up to 3 mg per kilogram of body weight a day, from all sources |
These figures come from EFSA. The US Food and Drug Administration also cites 400 mg a day, about two to three 350 ml (12 oz) cups of coffee, as an amount not generally linked with negative effects for most adults. Remember that coffee, tea, cola, chocolate and some painkillers add to your total.
Possible side effects
Too much caffeine can cause:
- A fast or irregular heartbeat and palpitations
- Raised blood pressure
- Anxiety, jitteriness and irritability
- Trouble sleeping
- Headaches
- Stomach upset and nausea
Caffeine lasts for hours in the body, so a can in the afternoon can affect sleep that night. People with heart conditions, high blood pressure or anxiety disorders, and people who take certain medicines, should talk to their doctor before drinking energy drinks.
Energy drinks and children
Medical experts advise against energy drinks for children and teenagers. The American Academy of Pediatrics says they’re not appropriate for children and adolescents and should never be consumed by them, because of the stimulants they contain. The FDA notes that too much caffeine in children and teens can cause a faster heart rate, palpitations, high blood pressure, anxiety and sleep problems. In the UK and EU, drinks with more than 150 mg of caffeine per liter must carry a warning that they’re not recommended for children or for pregnant or breastfeeding women, and many UK shops already refuse to sell them to under-16s.
For children who play sport, water is almost always the best drink. Our comparison of sports drinks vs water explains when sports drinks might be useful, and how they differ from energy drinks.
Sugar and teeth
A regular 250 ml energy drink contains about 26 g of sugar, close to the 30 g daily limit for free sugars recommended for adults by the NHS. A 500 ml can contains around 50 g. Energy drinks are also acidic, and sipping them over a long time exposes teeth to both sugar and acid. Our guide to sugar in soft drinks compares common drinks.
Sugar-free versions avoid the sugar but still contain the same caffeine and acids.
Mixing energy drinks with alcohol
Mixing energy drinks with alcohol is risky. The caffeine can mask the feeling of being drunk, so people may drink more and take more risks than they otherwise would, as the US Centers for Disease Control and Prevention warns. It doesn’t make you any less drunk. It’s best avoided.
Energy drinks and exercise
Caffeine can improve endurance and alertness, which is why some athletes use it. But energy drinks combine caffeine with sugar and other ingredients, and large amounts before hard exercise in heat can raise the heart rate. If you want caffeine before training, a coffee or tea is simpler, taken about 30 to 60 minutes before. Our guide to what to eat before and after exercise covers fueling.
Better ways to boost energy
If you rely on energy drinks to get through the day, the underlying problem is often sleep, irregular meals or dehydration.
- Sleep 7 to 9 hours if you can, at regular times.
- Eat regular meals with protein, fiber and whole grains to avoid energy dips. Our guide to foods for energy has ideas.
- Drink water through the day. Mild dehydration can make you feel tired.
- Take short movement breaks and get daylight, especially in the morning.
- Use coffee or tea in moderation if you want caffeine, without the added sugar.
If you feel tired all the time despite good sleep, see your doctor, as it can be a sign of conditions such as anemia, thyroid problems or depression.
Common questions
Is one energy drink a day bad for you?
For most healthy adults, one small can a day is within caffeine limits, but the sugar adds up, and daily use can disrupt sleep. A sugar-free version, or coffee or tea, is a better choice for regular caffeine.
Are energy drinks worse than coffee?
A small energy drink has about the same caffeine as a mug of coffee, but usually much more sugar. Black coffee or tea without sugar is a healthier way to get caffeine.
Can energy drinks cause heart problems?
In people with underlying heart conditions, large amounts of caffeine can trigger abnormal heart rhythms. Healthy adults are unlikely to have problems from moderate amounts, but drinking several cans in a short time, especially with alcohol or intense exercise, is risky.
Do energy drinks dehydrate you?
Moderate caffeine doesn’t cause dehydration in people used to it, but energy drinks aren’t a good choice for hydration during sport or hot weather. Water is better.
This article is general information, not medical advice. Talk to your doctor or a registered dietitian before making big changes to how you eat, especially if you have a health condition, take regular medication, or are pregnant or breastfeeding.
