Davis Allen Cripe, a healthy South Carolina teenager, downed a Mountain Dew, a cafe latte, and an energy drink — and then died suddenly last year.

This mixture of beverages, according to a South Carolina coroner, lead to a “caffeine-induced cardiac event causing a probable arrhythmia.”

Cripe’s untimely and highly unusual cause of death sparked questions about caffeine overdose and whether it’s now easier than ever to succumb to it.

It’s true that caffeinated drinks have become a bigger health concern — we know that the number of emergency room visits involving energy drinks has shot up in recent years. And doctors say kids and teens should never consume energy drinks because of the health risks of the caffeine and other stimulants in them.

But caffeine overdose is extremely rare, and usually involves high doses of caffeine in tablet or powder form, not beverages. “Caffeine, alcohol, marijuana — they are legal recreational drugs,” said Alex Wayne Jones, a toxicologist with Linköping University in Sweden who studied caffeine overdose, last May. “The safest of the three is going to be caffeine.” Here’s what you need to know about the risks of caffeine consumption and how not to overdo it.

Caffeine’s health benefits and risks

Caffeine is a central nervous system stimulant, and some 90 percent of adults in the world consume it in tea, coffee, soda, and other beverages daily.

This legal drug can boost alertness, cognitive performance, and even improve short-term memory. Drinking coffee is also associated with a range of other health benefits, including lowering the risk of cardiovascular disease and Type 2 diabetes. (That’s why the most recent US dietary guidelines suggested that drinking three to five cups per day could actually be part of a healthy diet.)

In the United States, we average about two cups of coffee — which total 100 to 200 mg of caffeine — a day. (A serving of an energy drink can have anywhere between 50 mg and 300 mg, and a can of soda typically contains less than 70 mg.)

Going above 400 mg daily, the recommended dose for adults, can cause unpleasant side effects that are probably familiar to you: jitteriness, insomnia, irritability. (The American Academy of Pediatrics recommends kids 12 to 18 years old stay below 100 mg of caffeine a day, or one cup of coffee.) That’s because caffeine can speed up the heart beat and disturb the body’s blood flow — which, in extreme cases, can be fatal.

Surely you’ve noticed that some people can drink six cups of coffee or more with no real adverse effects, while others get uncomfortably jittery on one cup. The reason? Some of us are genetically predisposed to be more sensitive to caffeine than others. Any underlying health problems (particularly involving the heart), as well as medications or other drugs, can also stimulate a stronger reaction to caffeine. And if you’re not a regular caffeine consumer, you can probably tolerate less caffeine than habitual users.

How much caffeine is deadly?

At toxic levels — we’re talking 30 cups of coffee consumed in a short period of time — the symptoms are a lot more serious: vomiting, abdominal pain, altered consciousness, and even seizures.

Death by caffeine, as in Cripe’s case, is typically caused by ventricular fibrillation — a rapid and irregular heart beat that disturbs the blood flow, leading to low blood pressure, loss of consciousness, and death.

But, as Tara Haelle wrote over at Forbes, these reactions are really, really uncommon from beverages alone. (One expert told her: “I’ve never known of a case where somebody died from three caffeinated drinks.”)

According to a review of the medical literature, there were only 45 caffeine-related deaths reported between 1959 and 2010. A more recent (2017) study (by Sweden’s Jones) found 51 — but also incredibly high levels of caffeine in the blood of the victims.

A single cup of coffee, which contains 100 mg of caffeine, brings caffeine blood levels up to about 5 or 6 mg/L. The blood levels of the people who died of caffeine overdose, according to the 2017 paper, averaged 180 mg/L, hence the 30 cups of coffee consumed in quick succession it would take to get to those lethal levels.

Energy drinks typically contain more caffeine than coffee — making them, at least in theory, easier to overdose on. A generously caffeinated energy drink might contain 300 mg of caffeine — so a person would need to quickly drink 10 to reach deadly blood levels of the stimulant. These drinks also contain other stimulants like guarana, taurine, and L-carnitine, and it’s these combinations that researchers worry the most about (but don’t fully understand), especially when mixed the beverages are mixed with alcohol.

Powdered caffeine poses a real health threat

Even so, medical complications from energy drinks are still rare. In Jones’ 2017 study on caffeine overdoses, about half of the deaths were suicides — and all involved caffeine in tablet or powder form, leading Jones to conclude, “It does not seem likely that toxic concentrations of caffeine can be achieved from over-consumption of caffeinated beverages alone.”

By contrast, caffeine supplements, like powdered caffeine, pack mega-doses of caffeine, much higher than what you’d typically get from a cup of coffee or even an energy drink. They are arguably the most dangerous form of caffeine, and the most likely to lead to serious health problems.

According to the FDA, caffeine powder is pure caffeine — and single teaspoon of the stuff is roughly equivalent to the amount in 28 cups of coffee. That’s pretty much toxic levels in a single teaspoon, which is why even small amounts of this stuff can cause symptoms much more severe than what you’d get from drinking one too many cups of coffee or tea.

Jeffrey Goldberger, a University of Miami cardiologist and expert on the health effects of caffeine, estimated the maximum potential amount of caffeine Cripe ingested from those three drinks was about 500 mg. “This would generally not fall into a range where people would say this is a lethal dose,” he said, adding that he was skeptical caffeine was the cause of death. Instead, he thinks there was probably another unrecognized health issue at play, or that this may just be one of the rare cases of sudden death at a young age.

“I think it’s important to be aware,” Goldberger said, “that caffeine is generally safe in the doses most people consume. But it does have the potential to be dangerous at extremely high doses, and there are people who have some sensitivities to it.”

The bottom line: If you stick to regular coffee, tea, and the odd energy drink — and avoid chugging these beverages in Herculean doses — you should be just fine.