How Much Caffeine Will Kill You?

Caffeine is the lifeblood of a productive civilization. Behind every bridge, monument, and skyscraper in America was a workforce fueled by caffeine. If society were Popeye, coffee would be its spinach. But, like everything good in life, if you do too much of it, it will kill you. That’s what the Food and Drug Administration (FDA) was trying to get across last week when they issued a stern warning against powdered caffeine. The official discouragement came after two people, an 18-year-old and a 24-year-old, overdosed from the stuff earlier this year. And those weren’t the first times someone has expired from caffeine, either. A 24-year-old woman in Scotland reportedly died earlier this month after taking too many caffeine-packed diet pills; a 23-year-old man in England died a few years ago after mixing two spoonfuls of caffeine powder into an energy drink at a party; and another man in the UK died from eating a tin of HERO Energy Mints last May, just to name a few.

But how much caffeine, exactly, does it take to kill you? The FDA says that you can safely consume about 400 milligrams per day, but it’s extremely unlikely that you’ll die even if you consume more than that (400 milligrams is roughly equal to four eight-ounce cups of joe). A study from 2005, which investigated two caffeine-related deaths, suggested that you’d have to ingest around five grams of caffeine—more than ten times the FDA’s figure—to overdose. Other sources suggest it’s more like ten grams, which would be like downing 50 shots of 5-Hour Energy. But in 2011 a girl died from “caffeine toxicity” after drinking just two cans of Monster—only 480 milligrams of caffeine, roughly the same amount in a Venti-sized Starbucks coffee.

So there are a lot of figures floating around out there. To get to the bottom of it, I asked Dr. Patricia Broderick who, among many other medical accolades, is the editor-in-chief of the Journal of Caffeine Research. Our conversation got off to a rough start (“Can somebody overdose on caffeine? No, no, caffeine can’t kill you,” was, oddly, the first thing she said), but she eventually told me something interesting: We just don’t really know how much caffeine it takes to put you in lethal danger. That’s because caffeine tolerance is a highly individualized thing. “Women are much more susceptible to the effects of caffeine than are men,” said Dr. Broderick, who added that young people also have much lower tolerances.

I found the same conclusions in a really old study on “factors affecting caffeine toxicity.” The study—basically a review of preexisting research—points out that caffeine affects people differently on the basis of age, gender, body mass, tolerance to the drug, any concomitant disorders, and any other drugs the person may have consumed. Caffeine is most toxic when consumed intravenously, but can also reach lethal levels by “oral, rectal, or subcutaneous routes.” The lethal dose depends on the administration of the drug, but it seems to be somewhere around 200 milligrams per kilogram—slightly more if you’re consuming it through your butt, and slightly less if you’re consuming it through your veins. (If you don’t feel like reading the academic study from 1967, try this handy calculator instead.)

This gets to what the FDA wrote in their statement about pure caffeine powder: It’s dangerous because “a single teaspoon [is] roughly equivalent to the amount in 25 cups of coffee.” But as Dr. Broderick reminded me, “Coffee is to a square as caffeine is to a rectangle“—they just aren’t the same thing. Drinking 25 cups of coffee is insane, but wouldn’t have the same immediate effect as snorting or swallowing pure powder. Part of that has to do with the actual substance (Dr. Broderick’s research suggests that coffee and tea have mitigating factors in caffeine absorption) and part of that has to do, again, with the method of administration. Think of it as the difference between swallowing an Adderall or crushing it up and huffing it. Caffeine is the same way: It will fuck you up way faster if you snort it in the powdered form, and you’re a lot more likely to overdose that way.

Given the relatively high dose of caffeine necessary to bring on death, you’d think reports of possible overdose would be pretty uncommon. Surprisingly, that’s not so. The American Association of Poison Control Centers receive thousands of calls each year from people concerned that their hearts are going to explode from caffeine. Last year, they received 3,033 of these types of calls calls about energy drinks alone, 1,835 of which were from people 18 and younger. Of course, nowhere near all of the people who called actually were overdosing on caffeine—they just thought they were. And many of these calls come from people who are also on other substances—alcohol, uppers, or other narcotics—so caffeine isn’t strictly responsible for all of this, but it’s still kind of crazy to think about.

The craziest thing is that getting high on caffeine isn’t even a good time. (We tested it out earlier in the year, when one of our writers tried smoking coffee. This is most definitely not recommended behavior.) In low doses, caffeine increases dopamine, which makes your brain feel nice. But when you take too much of it, that “reward” disappears, leaving you feeling jittery, anxious, and even physically ill. Taking too much caffeine can also make you feel irritable, headachy, tired—basically the opposite of what you’d expect to feel from caffeine. So there’s really no benefit in trying to edge toward that 200 milligram per kilogram figure, or injecting caffeine into your veins, or snorting spoonfuls of the powder. It won’t get you to that “high” place—and it just might make your heart feel like it’s going to explode.

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