What Is Caffeine Poisoning, and Should Us Coffee Chuggers Be Concerned? A Medical Toxicologist Tells All

Sure, some of my dietary habits could use some tweaking, but there’s one that I can’t imagine I’ll ever give up: starting my day with a delicious cup of coffee. *Cue the angels singing.*

Truth be told, the promise of a delicious cuppa—whether nice and hot via pour over, or crisp over ice via cold brew—and the rush of caffeine from it is pretty much the sole driving force that gets me out of bed every morning. I’ll usually reach for my second serving before noon, and perhaps another (and maybe even another) depending on the day at hand.

If you’re anything like me—or perhaps even go beyond a handful of cups of coffee or caffeinated bevs per day—it’s essential to know how much caffeine is too much. Sure, your body will probably let you know via jitters, jumpiness, or trouble sleeping… but is there a precise limit at which caffeine consumption turns toxic?

To scope out details on the potential for caffeine poisoning, we consulted Edward Boyer, MD, PhD, an emergency medicine physician specializing in medical toxicology at the Ohio State University Wexner Medical Center.

Caffeine sensitivity vs. caffeine poisoning

First, it’s worth knowing the difference between signs of caffeine sensitivity versus full-scale, all-hands-on-deck toxicity. “A poor reaction to caffeine would include jitteriness, as well as hypervigilance and increased urination,” Dr. Boyer says. Caffeine poisoning, on the other hand, “is characterized by an—often dramatically—elevated heart rate, very low blood pressure, vomiting, and seizures.”

“A poor reaction to caffeine would include jitteriness, as well as hypervigilance and increased urination,” Dr. Boyer says. Caffeine poisoning, on the other hand, “is characterized by an—often dramatically—elevated heart rate, very low blood pressure, vomiting, and seizures.”

You’ll likely have an idea of how much caffeine you can tolerate through trial and error. (Perhaps you love your daily java but adverse symptoms tend to kick in if you drink it on an empty stomach, or by the time you reach your third cup of the day.) Yet true caffeine poisoning warrants immediate medical attention. “It occurs when someone takes too much caffeine over a short period of time,” Dr. Boyer continues. “Anyone who has a seizure after using caffeine is critically ill and needs to be evaluated immediately.”

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How much caffeine can be toxic?

Dr. Boyer says that a few extenuating circumstances will dictate the potential for caffeine poisoning. “The amount of caffeine that can be toxic depends on how long a person took to ingest the caffeine, tolerance to the substance, and other factors,” he says. “Younger individuals and those who have limited tolerance are also at risk for caffeine poisoning.”

As far as precise numbers go, the FDA notes that toxic effects typically manifest with the rapid consumption of about 1,200 milligrams of caffeine in a short time frame. The amount of caffeine in your brew of choice will vary based on many factors—including but not limited to your brewing method and water temperature. Yet on average, you can anticipate ingesting somewhere around the following amounts per serving:

• 8-ounces brewed coffee: 96 milligrams
• 1-ounce espresso: 64 milligrams
• 8-ounces instant coffee: 62 milligrams

In addition, standard coffee isn’t the only source of caffeine you may sip on a given day. Decaf coffee contains traces of caffeine as well, at approximately 15 milligrams per 16-ounce cup. White, green, and black tea will contain anywhere from 14 to 62 milligrams per serving, and decaffeinated tea may contain up to 12 grams of caffeine per serving. Then, there are energy drinks, which typically pack anywhere from 80 to 150 milligrams of caffeine per eight ounces: the equivalent of two 12-ounce cans of caffeinated soda.

It could be worth doing some mental math to see how much caffeine you consume in a given day to ensure that your habits stay within a healthy range. “Some authorities [including the FDA] recommend that individuals limit their caffeine intake to 400 milligrams a day,” Dr. Boyer shares. Of course, this limit will vary based on how well you tolerate caffeine.

“Some authorities [including the FDA] recommend that individuals limit their caffeine intake to 400 milligrams a day,” Dr. Boyer shares. Of course, this limit will vary based on how well you tolerate caffeine.

The bottom line

Dr. Boyer notes that caffeine poisoning has become more common in recent years, especially due to the increased consumption of high-caffeine energy drinks and pure caffeine supplements. However, it’s not all doom and gloom: “Severe caffeine poisoning, which can be lethal, remains uncommon,” he notes. According to data from the National Library of Medicine, less than three dozen deaths from caffeine poisoning have been reported over the past decade. Plus, immediate medical treatment at the onset of caffeine poisoning—signaled by a massive spike in heart rate, vomiting, and seizures—offers highly favorable outcomes.

These points considered, you (literally and figuratively) shouldn’t lose sleep over enjoying one or even a few cups of coffee per day. But if you experience any telltale symptoms associated with caffeine intake—or realize that you may be teetering a little too close to that 400-milligram daily upper limit—it could be worth scaling back your sips. I, for one, will continue to enjoy my couple of caffeinated cups until lunchtime… but I’ll probably think twice before going well beyond that the next time I’m in need of a midday pick-me-up.