Energy Drink Caffeine Overdose: How Much Is Too Much?

Posted on April 17, 2014 | Last updated March 8, 2025

How Much Caffeine Causes Acute Caffeine Overdose?

Caffeine Toxicity and Lethal Doses from Energy Drinks
For the average adult, how much caffeine does it take to reach acute caffeine toxicity? In reality, there is no clear-cut threshold—it varies based on individual factors such as body type, age, and the amount consumed per kilogram of body weight in a short period.

Here, we'll outline some general guidelines regarding caffeine toxicity and lethal doses. However, as mentioned earlier, individual differences play a significant role. Just because you see "○○mg is safe" on the internet doesn't mean it applies to everyone. Be mindful of overconsumption!

Author information Author: Energy Drink-kun

In 2001, while living in the United States, I encountered energy drinks through the dance scene and was deeply impressed. After returning to Japan, I found that energy drinks were considered novelty beverages, so I established a comprehensive website in 2013 to share the true appeal of energy drinks. As an energy drink enthusiast, I began drinking them seriously again, collecting over 7,000 varieties of energy drinks from various countries. I am also active as a critic and expert, receiving media interviews.

Ingesting 6.5 mg/kg of caffeine within an hour can cause acute caffeine toxicity in about half of people.

For an average adult, how much caffeine does it take to develop acute caffeine toxicity? The key factor is not just the amount consumed but how quickly it is consumed.

▼For a 70 kg person: 6.5 mg/kg of caffeine in one hour is the threshold for acute caffeine toxicity in about half of cases.

3 cans (approx. 1.5L) of the U.S. Monster Energy 473ml (160mg per can)
3.5 cans (approx. 890ml) of the Japan Monster Energy 355ml (142mg per can)
6 cans (1.5L) of the Japan Red Bull 250ml (80mg per can)

100% Risk of Acute Caffeine Toxicity at 17 mg/kg Within Three Hours

▼For a 70kg Individual: 1,190mg in Three Hours is the Critical Limit

7.5 cans (approx. 3.5L) of the U.S. Monster Energy 473ml (160mg per can)
8+ cans (approx. 3L) of the Japan Monster Energy 355ml (142mg per can)
15 cans (3.7L) of the Japan Red Bull 250ml (80mg per can)

Hmm… Japan’s Monster Energy is really pushing the limits... (；´∀｀)
That said, consuming this much within three hours seems nearly impossible.

For people with lower body weight—many in Japan weigh less than 70 kg—the threshold for acute caffeine toxicity could be even lower. Even those with higher body weight should not be overconfident, as individual tolerance varies. Some may experience toxicity symptoms with fewer cans.

The key point here is that acute caffeine toxicity occurs when large amounts are consumed in a short period.
Drinking 2–3 cans over the course of 24 hours doesn't necessarily cause acute caffeine toxicity.

If you’re thinking, “I drank two cans of Monster in a day, is that okay?” → If it’s just for one day, there’s usually no need to worry.

Symptoms of Acute Caffeine Toxicity

Caffeine Toxicity and Lethal Doses from Energy Drinks
Most people notice when something feels off—if you think, "This feels bad," chances are it's acute caffeine toxicity.

Common symptoms include restlessness and anxiety. More severe cases can lead to hallucinations and delusions—though reaching this level is extreme. Personally, I’ve experienced heart palpitations after drinking too much, but nothing beyond that.

In conclusion, drinking multiple energy drinks in rapid succession can cause acute symptoms, which may indicate caffeine toxicity.

Chronic Caffeine Toxicity

Caffeine Toxicity and Lethal Doses from Energy Drinks
Regular caffeine intake of 250mg per day may lead to chronic symptoms, and individuals sensitive to caffeine may experience effects even at 100mg per day. This is an amount many people exceed—just three cups of coffee (80–100mg each) can surpass this threshold.

For me personally, drinking multiple energy drinks daily sometimes led to heart palpitations even on days when I only had one. Whether this was psychological or caffeine-related is unclear, but when it happens, I take a break from energy drinks and coffee for a few days.

Treatment for Caffeine Toxicity

There are no specific antidotes or counteracting medications, so the standard treatment is to rest and wait it out. In severe cases, hospitalization and medical supervision may be required, sometimes including gastric lavage.

Lethal Caffeine Dose from Energy Drinks

The lethal dose of caffeine varies based on age, body size, and individual metabolism, but it is generally around 5–10g. While some reports link deaths to energy drinks like Red Bull or Monster, direct causation has not been established.

To put this into perspective, here’s how much caffeine you’d need to reach 5 grams:

▼Fatal Dose of 5g Caffeine

31+ cans (approx. 14L) of the U.S. Monster Energy 473ml (160mg per can)
35+ cans (approx. 12.5L) of the Japan Monster Energy 355ml (142mg per can)
62.5 cans (approx. 16L) of the Japan Red Bull 250ml (80mg per can)

For younger people, those with liver issues, or those with lower caffeine tolerance, the lethal dose may be lower. However, drinking 15L of liquid is an extreme challenge in itself.

For a detailed list of caffeine content in various energy drinks, check this page.