Fact check: Extremely unlikely to overdose on coffee, but rapid caffeine consumption has risks

The claim: Drinking 42 cups of coffee in one sitting would be lethal

Caffeine is the world's most popular psychoactive drug, with American adults consuming 1.87 cups per day on average in 2020. But unlike other drugs, serious overdoses of caffeine are extremely rare. Why is that? And how much is too much?

A meme circulating on social media purports to have one answer. A tweet that has gone viral in widely-shared screenshots says that it would take 42 cups of coffee – that's about two and a half gallons – to induce a fatal overdose.

“If you drank 42 cups of coffee in one sitting, the caffeine overdose would kill you,” the tweet in the screenshot, from the Twitter account @Fact, says.

“So 41 is the limit,” reads one humorous reply

Several Facebook users have shared the meme, including one whose Nov. 14 post garnered over 1,100 reactions. The @Fact account has tweeted the claim several times, including in January and June 2021.

An administrator for the @Fact page told USA TODAY that their source was a New York Times article from 2011 that said it would require consuming at least 42 cups of strong coffee in one sitting to consume the minimum lethal dose of 5,000 mg of caffeine.

However, the article also said that "it would be very hard, probably impossible, to ingest enough caffeine to kill yourself by drinking ordinary coffee." According to our research, this is accurate.

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"I don't think you could possibly drink 42 cups of coffee fast enough for it to kill you," Jennifer L. Temple, director of the Nutrition and Health Research Lab at the University of Buffalo, told USA TODAY in a phone interview.

However, that's not to say it's impossible to overdose on 42 cups of coffee or an equivalent amount of caffeine. While typical-strength coffee is unlikely to kill a person, large quantities of highly caffeinated coffee or other products can be dangerous in much lower amounts.

USA TODAY reached out to users who shared the claim for comment.

Nearly impossible to overdose on regular brewed coffee

Not only would the caffeine in 42 cups of typical brewed coffee fall below the FDA's current estimate of a lethal dose of caffeine, it wouldn't be absorbed all at once, a caffeine researcher told USA TODAY.

The FDA estimates a lethal dose of caffeine is between 10,000 and 14,000 mg, though smaller amounts can be life-threatening in children and sensitive individuals, such as people with underlying heart conditions.

Basing our calculation on a standard eight-ounce cup of brewed coffee containing 100 mg of caffeine per cup, 42 cups would have around 4,200 mg of caffeine, less than half of the lethal amount.

And the time it takes to drink that amount of coffee would allow the body to metabolize some of the stimulant, Temple said.

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However, that doesn't mean it's impossible to overdose on coffee in general. Our calculation is based on standard-strength coffee, which contains between 80 mg and 100 mg of caffeine, but some brands of coffee are much stronger. For example, Death Wish coffee contains almost 500 mg per cup, according to Caffeine Informer.

Possible to overdose on less caffeine, especially when highly concentrated

While typical-strength coffee forces you to spread out your caffeine consumption, giving you time to take stock of its effect and metabolize the stimulant, highly concentrated products can overwhelm your body and put you at risk of an overdose at far lower amounts than is in 42 cups, experts say.

If consumed all at once or in a short time period, 4,200 mg of caffeine is a toxic and potentially fatal dose.

“If somebody were to say, ‘4200 milligrams of caffeine (at once) will kill you,’ I would say, ‘Yeah, there's a good chance,'" Temple said.

The FDA estimates a toxic dose to be around 1,200 mg of caffeine, which is equivalent to just 0.15 tablespoons of pure caffeine. In some people, consuming this amount rapidly can lead to serious events such as seizures, tachycardia and arrhythmia.

In addition, people have differing levels of sensitivity to caffeine based on weight, tolerance, speed of consumption and underlying conditions such heart conditions, Temple said.

The product you're consuming also makes a difference. For example, many energy drinks also contain another stimulant called taurine that may amplify the effects of caffeine, Forbes reported.

Temple said she would advise people who are taking highly concentrated caffeine products like caffeine pills and energy shots to slow down consumption to prevent negative effects.

"Don’t start taking more and more and more and more because you don't feel the effects of the caffeine immediately," she said, "because then, you could potentially overdose."

As USA TODAY reported, a South Carolina teenager died of a "caffeine-induced cardiac event" in 2017 after consuming a large Diet Mountain Dew, a McDonald’s latte and an energy drink in roughly two hours. Reuters estimated the teen consumed under 500 mg of caffeine.

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The way that drinking a beverage slows down consumption, as well as the overwhelmingly negative effects of caffeine overconsumption, generally prevents overdoses, Temple said.

“The way that most people consume caffeine is generally safe because once they start feeling the non-lethal negative effects, they'll stop consuming it,” she said. “People don’t like to feel shaky and jittery and nauseous.”

Around 400 milligrams of caffeine per day, which is equivalent to 4-5 cups of coffee, is not generally associated with negative health effects, the FDA says.

Our rating: Missing context

Based on our research, we rate the claim that drinking 42 cups of coffee in one sitting would be lethal as MISSING CONTEXT, because without additional information it could be misleading. The post contains no units of measure, and there's wide variation in the caffeine content of different brands of coffee. However, it's extremely unlikely, if not impossible, to suffer a fatal overdose by drinking 42 cups of standard brewed coffee, which would contain around 4,200 mg of caffeine in total. On the other hand, consuming far lower amounts of caffeine in powdered or highly concentrated form, including highly caffeinated coffee, could put a person at risk of an overdose.

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This article originally appeared on USA TODAY: Fact check: Unlikely, if not impossible, to overdose on brewed coffee