About Energy Drinks

How Harmful Are Energy Drinks?

A large energy drink bottle can flood your body with up to 294 mg of caffeine in one sitting. Look at a label and you’ll also notice that the average Monster contains way more than your morning cup o’ joe, namely sugar and other ingredients like taurine, ephedrine, guarana, and ginseng. All those “extras” act as stimulants, enhancing caffeine and sugar’s effects, and throwing your body into overdrive. 

More troubling? The efficacy—and health risks—of those additives are largely unknown, said Maria Pagano, M.S. R.D., C.S.C.S. and Equinox Tier 4 coach.

So before you reach for an artificial pick-me-up, Pagano explains what’s going on under the hood while you’re sipping.

Your brain: Caffeine blocks the effects of adenosine, a brain chemical that helps you sleep (which is why too much can lead to insomnia). But it also fires off neurons in your brain to keep you alert, causing your pituitary gland to initiate the “fight or flight” response. That’s your body’s natural reaction to prepare for a threat.

Your bloodstream: After the “fight or flight” response is activated, your pituitary gland releases adrenaline, which sends a signal to your liver to pump more glucose (a.k.a energy) into the bloodstream.

Your heart: Adrenaline makes your heart beat faster and your eyes dilate, effects that can last longer than you might like. In fact, a recent German study found that healthy people who drank caffeine and taurine-packed energy drinks saw increased heart contraction rates up to an hour later.

Back to your brain: With more glucose in your bloodstream and your body in fight-or-flight mode, the increased dopamine levels trick your brain in to believing that you have more energy than you really do.

Your skin: Sweat excessively while exercising and you’ll lose water and electrolytes—both of which sports drinks work to replace. Reach for an energy drink after that, though, and you’ll only dehydrate yourself more.

Your body: Too much caffeine can produce a diuretic effect, which can also mean dehydration. If you overdo it, you could feel jittery, anxious, and irritable from too much of the stimulant and a lack of water.


More Information On Just How Bad Energy Drinks Are?

Answer by Diana Koelliker, MD

In recent years, a number of energy drinks have entered the market to provide a quick boost of energy.  These drinks usually contain high levels of caffeine and other additives, such as taurine, ginseng and carnitine that act as stimulants. 

The average eight ounce cup of coffee contains about 100 mg of caffeine.  Some energy drinks contain as much as 500 mg of caffeine per serving in addition to the other stimulants found in these beverages. 

Because energy drinks are sold as nutritional supplements, they are not regulated as foods.  Therefore, the FDA does not regulate or limit the amount or content of ingredients in these drinks; you may not know exactly what you are drinking when you consume these products.

So, does that necessarily mean these drinks are bad for you?  In small doses, caffeine is a pretty innocuous substance.  However, in high concentrations, it can cause sleep disturbances, anxiety, restlessness, elevation in blood pressure and heart rate, abnormal heart rhythms (arrhythmia), seizures and even death.

As an Emergency physician, we certainly have seen an increase in visits related to energy drinks. In 2005 there were about 1,100 ER visits in the US related to these drinks; in 2008 there were more than 16,000 visits. The numbers continue to rise. 

What’s worse, the trend of combining energy drinks with alcohol is popular with college students and young adults. This may be due to a misconception that caffeine counteracts alcohol; it does not.

A high caffeine content stimulant effect can prevent a person from becoming sleepy, but it does not prevent impairment, nor does it quicken reaction time or motor skills.  Caffeine and alcohol together can lead to increased participation in risky behavior, like driving.  It also can lead to what I call the “superman effect,” where the person believes they can skateboard down a flight of stairs. The consequences can be dangerous and even deadly.

Energy drinks are especially dangerous for children and adolescents. The American Academy of Pediatrics recommends energy drinks should never be consumed by children or adolescents. 

High levels of caffeine have been associated with harmful neurologic and cardiovascular effects in children, and drinks containing stimulants should never be given for hydration or as a supplement to young persons. Parents should warn teenagers and young adults of the dangers of mixing these drinks with alcohol.

In summary, if you have a history of high blood pressure, heart problems, seizures or if you are pregnant, it’s best to steer clear from energy drinks.  Any person, regardless of their health status, can be at risk of side effects of these beverages if too much is consumed or if they are consumed in association with alcohol. Finally, there is no place for energy drinks in the diet of a child or adolescent. 

Telluride Medical Center 500 West Pacific Avenue • PO Box 1229 • Telluride, Colorado 81435 (970) 728-3848


Top 10 Energy Drink Side Effects

Recent research in Australia has highlighted the risks with over-consumption of energy drinks. This data was gathered from 7 years of calls to the Australian Poisons Center.

Listed in order of most common to least common:

  1. Palpitations / tachycardia
  2. Tremor / shaking
  3. Agitation / restlessness
  4. Gastrointestinal upset
  5. Chest pain / ischaemia
  6. Dizziness / syncope
  7. Paraesthesia (tingling or numbing of the skin)
  8. Insomnia
  9. Respiratory distress
  10. Headache

Learn More

Overdose Symptoms – Facts and Fiction
Top 10 Caffeine Withdrawal Symptoms

Energy drinks contain supplements and vitamins and are required to list warnings on the label about consuming more than the recommended serving.

In moderation most people will have no adverse, short term side effects from drinking energy drinks, however, the long term side effects from consuming energy drinks aren’t fully understood as of yet.

Potential Problems from Specific Ingredients

Let’s take a look at the most common energy drink ingredients and list the potential side effects that could result from ingesting too much of them from your favorite energy drink.


This is the most common energy drink ingredient and one of the most widely consumed substances in the world.

Caffeine tolerance varies between individuals, but for most people a dose of over 200-300mg may produce some initial symptoms: restlessness, increase heartbeat, insomnia.

Higher dosages can lead to more (see more about caffeine overdose here):

  • Increased blood pressure
  • Heart palpitations
  • Gastrointestinal disturbance (diarrhea)
  • Increase urination
  • Dizziness, irritability, nausea, nervousness, jitters.
  • Allergic reactions can include; rash, hives, itching, difficulty breathing, tightness in the chest, swelling of the (mouth, face, lips, or tongue), diarrhea, shakiness, trouble sleeping, vomiting.
  • Headache and severe fatigue from withdrawal.
  • Breast shrinkage in females.
  • Painful withdrawal symptoms if not consumed.

Caffeine can be found in other ingredients such as guarana,  green tea extract, and coffee extract as well as many other names, so be aware of this when reading energy drink labels.

Please consult the caffeine database for an exhaustive list of caffeine in energy drinks (and other drinks). This is updated weekly.

Adrenal Fatigue

Some people can become tired after consumption of caffeine. This is a symptom of adrenal fatigue where the body’s adrenalin system has become overtaxed by constant high caffeine intake. The answer is not to increase caffeine even more – but to reduce, detox, and get the adrenal glands back to a healthy state.

Remember it’s hard to pinpoint a safe dose because it varies from person to person and according to a person’s tolerance.

See our Caffeine Safe Dose Guide here.

Between 500 milligrams to 1000 milligrams in a 24 hour period will probably lead to some of the more severe side effects.

Click here to find out how much caffeine in different energy drinks would be deadly.


Most energy drinks are high in sugar in the form of high fructose corn syrup and/or cane sugar. Some use creative names to make their version of sugar seem healthier, like “natural cane juice” or they’ll call it “glucose”.

  • High sugar drinks are linked to the obesity epidemic
  • Tooth Decay
  • Increases risk of type 2 diabetes.
  • The sugar in energy drinks causes blood sugar and insulin spikes which later result in a “crash like” feeling.


No side effects from Taurine in energy drinks have been documented.  Some countries (France, Denmark, and Norway) originally banned energy drinks because of their taurine content, but have since accepted that taurine consumption is safe based on the evidence to date.

The amounts placed in energy drinks are well below what would be needed for therapeutic benefit or for any potential side-effects.

B Vitamins

  • More than 35mg of Niacin (B3) can cause flushing of the skin. Intake of 3000mg or more can result in liver toxicity.
  • More than 100mg of B6 can cause sensory nerve problems (burning sensation) or skin lesions.


No known side effects have been reported, but ingesting large quantities has been linked to diarrhea. Large doses have been used to treat certain psychiatric disorders.


  • Some studies have linked it to sleeplessness, while others refute this.
  • Other possible symptoms include; low blood pressure, edema, palpitations, tachycardia, cerebral arteritis, vertigo, headache, insomnia, mania, vaginal bleeding, amenorrhea, fever, appetite suppression, pruritus, cholestatic hepatitis, mastalgia, euphoria, and miscarriage.


While no side effects have been reported there’s still debate on its safety. However many countries including Canada, England, Germany, and France have concluded that it is not a safety concern.

Artificial Sweeteners

If you drink sugar-free energy drinks you may consuming any number of artificial sweeteners. There is always debate around the health effects of these (particularly aspartame) all major health institutions regard them as safe.

Ginkgo Biloba

Gingko is a herb, and can cause some minor side effects in some people:

  • nausea, diarrhea, headaches, dizziness, heart palpitations, and restlessness.
  • Can interact with other medication such as blood thinners and anti-depressants.
  • A recent study found that ginkgo caused thyroid cancer in rats.


  • vomiting, nausea, headache, diarrhea, stuffy nose, restlessness and sleeping difficulty.


This amino acid is derived from green tea and many energy drinks and shots have begun putting “green tea extract” in their products.

It produces a different type of alertness than caffeine and there hasn’t been any scientific evidence of it causing adverse side effects. Some have reported feeling light-headed when consuming a dose of more than 300mg of L-Theanine.

What is Safe For You?

Energy drinks should not be a staple. If you need caffeine then coffee is a healthier source.

Despite a number of alarming reports of overdose in recent years, for most people energy drink consumption is fine in moderation.

Many reported side effects are anecdotal – being reported from patient’s records. It’s hard to say which ingredient actually caused the problems if the patient was ingesting several combinations of these at one time.

Be Careful of Pre-existing Conditions

If you or your child has a pre-existing heart condition of any sort – they should not be consuming energy drinks. In general it is better to avoid the larger drinks (i.e. Mega Monster has a massive 240mg caffeine in its 24 fl oz giant can), and stick to smaller 8oz cans.

If you drink responsibly and use energy drinks when you need a boost of energy and not use them as a replacement for water, then you most likely will avoid energy drink side effects.