When Does Caffeine Become Deadly?

This week the internet was taken aback by the story of the death of 16-year-old Davis Allen Cripe. According to the coroner's report, after drinking a soda, a coffee, and an energy drink all in a short amount of time, Cripe suffered a change in heart rhythm that ultimately took his life. His cause of death was officially ruled a "caffeine-induced cardiac event." But what does that really mean? And how can caffeine — a substance that many of us consume daily — be so dangerous?

It all comes down to the dose. Most of us are totally fine with the caffeine that comes in three or four cups of coffee. But the USDA recommends that we stay below that limit, which amounts to about 400 mg of caffeine, the Mayo Clinic says.

With higher doses of caffeine, the side effects start to become more noticeable. If you decide to have just one extra shot of espresso, for instance, you might feel your heart rate increase, be a bit irritable, and just feel "jittery." You may also have trouble falling asleep that night.

In general, the level at which caffeine becomes toxic is when you've ingested 10 grams (the equivalent of 50 to 100 cups of brewed coffee, depending on the strength). However, as PopSci explains, the problem is that the exact caffeine limit for you depends on your weight and the way you're getting that caffeine (e.g. in a Starbucks Frapp versus an energy drink). The weight factor makes sense — it's similar to the way that the same amount of booze can make differently-sized people feel very different levels of drunk. And if you're puzzled about why the delivery method matters, it's due to the level of dilution of caffeine (more water means it's more diluted, which means you'll have to drink more of it to get fully caffeinated) and what else might be lurking in that drink, which may be other stimulants or even alcohol (remember Four Loko?).

So the amount of caffeinated beverages that's dangerous specifically for you may be a bit lower or higher than it is for your friends. Plus, drinking large amounts of caffeine along with alcohol or an already-elevated heart rate (e.g. after a workout) makes your chances for trouble much higher. And if you know you have a heart condition, you will have probably already had a conversation about caffeine consumption with your doctor. (According to the coroner's report, Cripe did not have a heart condition.)

Still, caffeine-related deaths are obviously quite rare. But that doesn't mean you shouldn't try to keep track of the amount you're drinking. And that's not always an easy task: The strength of your drip coffee can change depending on who's making it, sodas from restaurants obviously don't display their caffeine content on your cup, and, honestly, who really reads all the tiny words on an energy drink can?

That's what makes Cripe's story such a tragic reminder of the common sense advice far too many of us forget every day: Be aware of the caffeine you're actually having and give it the chance to work before downing more.