A college has been fined 400,000 for almost killing two students who participated in a study on caffeine and exercise. Researchers at Northumbria University accidentally administered 30 grams of caffeine to the students instead of 0.3 grams — the equivalent of 300 cups of coffee. After being treated with dialysis, both students were able to make a full recovery, save for some short-term memory loss. That’s surprising — consuming way less caffeine than that could kill a person.

Caffeine is a central nervous system stimulant that has been used by humans to jumpstart their systems for more than 1,000 years. The FDA classifies it as both a drug and a food additive. As the most widely used drug on the planet, caffeine stimulates the brain to increase alertness, raises the amount of acid in your stomach, and gives you a short burst of increased blood pressure. Too much of it, however, can also kill you.

Doctors generally agree that consuming 400 milligrams of caffeine a day is safe for most healthy adults. That’s the equivalent of four cups of brewed coffee and 29,600 fewer milligrams than the students consumed.

Too much caffeine can kill you.
Too much caffeine can kill you.

The standard four-cup rule isn’t ubiquitous, though; several factors, like height and weight, affect how much you’ll be affected by caffeine. According to the Caffeine Calculator, a safe amount of coffee for a 191-pound man — the average weight of an American male — is 3.2 cups per day. If that 191-pound man had 80 cups of coffee, he will probably die. Comparatively, 66.6 cups of coffee will most likely kill a woman who weighs 159 pounds — the weight of the average American female.

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But caffeine overdose is an uncertain science: Jack James, Ph.D., the editor of the Journal for Caffeine Research, told Popular Science that the overdose for adults is about 10 grams of caffeine. However, a 2005 study found that two fatal overdoses occurred after the victims consumed 5 grams of caffeine.

“Caffeine toxicity. . .is not well understood,” James told Popular Science. “There is speculation in the literature regarding the possibility of some individuals having a peculiar sensitivity to caffeine, but there is not clear definition or understanding of what such sensitivity might be.”

And what might caffeine overdose look like, right before a person dies? Symptoms include reactions like a fever, hallucinations, convulsions, and an irregular heartbeat. Regularly overdosing on caffeine can even cause psychosis in otherwise healthy people.

Photos via Giphy (1, 2)