A Hardcore Enthusiast Explains the Dangerous Side Effects of Monster Energy

The Overwhelming Fatigue After Drinking Monster Energy

Effects of Caffeine

This is most likely just accumulated fatigue. Or, if you were already sleep-deprived and forced yourself to stay awake with caffeine, it's simply the drowsiness catching up to you.

However, a single can of Monster Energy contains 142mg of caffeine, which isn't particularly high—it’s about the same as a cup of coffee. So, it's unlikely that just one can would be enough to completely prevent sleep. That said, people with extremely low caffeine tolerance, who can't sleep even after a single cup of coffee, might be affected.

Effects of Sugar

It’s also possible that the sugar in Monster Energy temporarily raises your blood sugar level, leading to a feeling of fatigue once it drops. But the sugar content in Monster Energy is about the same as that of sodas like Coke or Fanta, so there’s no need to worry too much. If this were a real issue, then it would mean sodas in general have "side effects" too.

If you experience overwhelming fatigue after drinking a sugary soda, there might be an underlying health issue. In that case, I’d recommend seeing a doctor.

Does the Caffeine in Monster Energy Keep You Awake?

Some people might struggle to sleep after consuming the caffeine in Monster Energy. If I had to name one actual side effect, this would be it.

As I mentioned earlier, people with low caffeine tolerance can have trouble sleeping even after just one cup of coffee. Since the caffeine content of Monster Energy isn't much different from coffee, those who have difficulty sleeping after coffee should be cautious.

For most people, drinking Monster Energy at night doesn’t prevent sleep, which often leads to the claim that "Monster Energy has no effect!" But that’s hardly surprising since the actual impact of the drink is quite limited.

That said, if you drink two or three cans in a short period, your caffeine intake will increase significantly. This could lead to difficulty sleeping or even acute caffeine intoxication.

Caffeine Intoxication from Monster Energy

In the U.S., there have been several incidents where caffeine, including that from Monster Energy, was believed to be a contributing factor in fatal accidents. In Japan as well, there have been cases of fatalities linked to excessive caffeine consumption from energy drinks, coffee, and caffeine pills. Emergency hospitalizations due to excessive caffeine intake are also reported frequently.

However, it's extremely unlikely that drinking only Monster Energy would lead to severe health consequences. In most cases, you'd have to force yourself to consume a massive amount before experiencing acute caffeine intoxication.

For more details, check out the Caffeine Intoxication from Energy Drinks page. To develop acute caffeine intoxication, a person weighing 70kg would need to consume about 890ml (three and a half cans) of a 355ml Monster Energy in a short period. At this level, about half of individuals would experience acute symptoms. To reach a 100% probability of acute symptoms, you’d have to drink approximately 3 liters (around 8 cans) in a short span.

The key point here is "in a short period." Drinking three cans over several days is not an issue, as I’ve explained earlier. So, there’s no need to worry about "side effects from drinking a can of Monster Energy every day." Many energy drink enthusiasts consume one or two cans daily without problems.

Symptoms of acute caffeine intoxication include heart palpitations, dizziness, and nausea. Under such conditions, continuing to drink more Monster Energy becomes increasingly difficult.

Fatal Incidents Linked to Monster Energy

About the Fatal Incident in the U.S.

One of the most famous cases in the U.S. involves a girl who allegedly died after consuming two 710ml mega-sized cans of Monster Energy. Some sources, like Wikipedia and NAVER Matome, incorrectly state "700ml," but the correct size is 710ml.

There is no information available about whether she had also consumed caffeine pills or other sources of caffeine. So, let's look at how 480mg of caffeine, the amount she consumed, compares to established safety guidelines based on information from the FDA.

The Impact of 480mg of Caffeine

According to the U.S. Food and Drug Administration (FDA), the Department of Health and Human Services, and the Department of Agriculture, healthy adults can safely consume up to 400mg of caffeine per day without an increased risk of chronic toxicity, including cardiovascular disease.

[Reference Article (English)] FDA Article

However, children and individuals with heart conditions do not fall under this guideline and should be cautious. In general, though, consuming around 400mg of caffeine is unlikely to be fatal.

How Much Caffeine Would It Take to Be Fatal?

As mentioned in the Caffeine Intoxication Page, consuming more than 5,000mg of caffeine is considered potentially fatal. The girl in the U.S. case reportedly consumed 480mg, which is about one-tenth of the lethal dose.

To reach a lethal dose, you would need to drink about 35 cans (12.5 liters) of Japanese Monster Energy in a short time. Again, this is not over several days but all at once.

It’s Nearly Impossible to Die from Monster Energy Alone

As you can see, it would be extremely difficult to consume a lethal dose of caffeine from Monster Energy alone. Before reaching that amount, acute symptoms would likely prevent you from drinking any more.

For comparison, in the U.S., you would need to drink about 31 cans (14 liters) of Monster Energy to reach a fatal dose. The reason why Japan’s Monster Energy requires fewer cans is that its caffeine concentration per 100ml is higher than the American version—something many people might not be aware of.

Do Ingredients in Monster Energy Cause Side Effects?

Some people suspect that ingredients other than caffeine in Monster Energy might cause side effects. But if you check the ingredient list on the can, you’ll see that most of them are present in very small amounts.

Ingredients like ginseng, arginine, and D-ribose (in the Japanese version) are included in such tiny quantities that they don’t have a significant effect on physical performance or cognitive function. This applies to both the Japanese and American versions of Monster Energy.

While energy drinks may have some impact on the body, drinking Monster Energy won’t magically enhance your abilities in any drastic way.

For Those Who Drink Monster Energy Every Day

Be Mindful of Excess Sugar and Calories

Drinking Monster Energy daily means consuming extra calories and sugar. While it may not directly lead to diabetes, it’s not the best dietary habit, especially for people with a sedentary lifestyle, such as middle-aged office workers who don’t exercise.

For those who are overweight, energy drinks and sodas may be a hidden source of excessive calorie and sugar intake.

Watch Your Overall Caffeine Intake

Even if you space out your energy drink consumption, drinking multiple cans daily leads to chronic caffeine intake, which can negatively affect sleep quality. If you also drink coffee, green tea, black tea, or barley tea regularly, you should be aware of your total caffeine intake.

However, this isn’t unique to energy drinks. Excessive consumption of anything is bad for your health. That’s just common sense, right?

In the end, Monster Energy doesn’t have particularly strong effects, so calling them "side effects" might not even be accurate.

Just be mindful of overconsumption and enjoy the different flavors!