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Dark roasted and dangerous: Everything you should know about caffeine intoxication

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For many Americans, a morning routine is not complete without a cup of joe. The National Coffee Association reports the average American drinks just over three cups daily. And some people opt to get their caffeine through energy drinks or caffeine pills.

While everyone’s tolerance is different, there is a limit to how much caffeine people can have in their systems. Jittery fingers and a racing heartbeat are common signs that you’re over-caffeinated. In rarer scenarios, an overconsumption of caffeine can lead to a state called caffeine intoxication or caffeine overdose.

Caffeine intoxication occurs when a person has dangerously high levels of caffeine in the system. It creates a spectrum of unpleasant and severe symptoms, such as trouble breathing and seizures. There are a few cases where people have died from caffeine intoxication.


While rare, there is always a potential for caffeine intoxication if a person is drinking irresponsibly. Recognizing the signs and factors that increase the risk of a caffeine overdose can help you avoid it in the first place.

How much caffeine is too much?

Caffeine intoxication is more than the headache you get from drinking too much expresso. It happens when people ingest an excessive amount of caffeine. The US Food and Drug Administration defines this limit as anything more than 400 milligrams of caffeine daily for healthy adults. This is equivalent to four or five cups of coffee.

Consuming slightly more than 400 milligrams of caffeine is not enough to kill or permanently impair someone, said Erin Palinski-Wade, a registered dietitian at EKP Nutrition Communications in New Jersey. The average adult will likely feel anxious and irritable. The more toxic effects of caffeine intoxication appear when people have 1,200 milligrams, about 12 cups of coffee, in their system.

That cup of morning coffee may affect you differently than your friend. - Oleg Breslavtsev/Moment RF/Getty Images
That cup of morning coffee may affect you differently than your friend. - Oleg Breslavtsev/Moment RF/Getty Images

Caffeine intoxication ranges from unpleasant to life-threatening

Caffeine intoxication creates a variety of severely damaging effects on the body.

Nima Majlesi, director of medical toxicology at Staten Island University Hospital, said the stimulant effects of caffeine disrupt your normal heart rhythm, leading to abnormal heartbeats and possible cardiac arrest. Additionally, Palinski-Wade said people with a caffeine overdose may experience gastrointestinal issues such as vomiting and diarrhea.

Since coffee increases urination, Majlesi said severely over-caffeinated people risk flushing out essential minerals, especially potassium. Low potassium levels, or hypokalemia, can damage muscles to the point of possible paralysis, cause difficulty breathing from weakened respiratory muscles and prevent kidneys from doing their job.

A number of caffeine intoxication symptoms are also neurological. Documented cases have reported anxiety, hallucinations, migraines, swelling of the brain and seizures.

While extremely uncommon, caffeine intoxication can turn lethal. Most accidental caffeine-related deaths are related to taking multiple high-dose caffeine pills. Caffeine pills are not FDA-regulated, so their doses vary across brands.

Palinski-Wade said most caffeine pills have around 300 milligrams, so taking a second one already would exceed the recommended caffeine intake of 400 milligrams. “Like with any supplement, caffeine pills should be used with caution,” she added. “I would even discuss it with your health care provider because pills are absorbed in the body quicker, and the amount might put you at risk for more side effects.”

What to do if you suspect a caffeine overdose

If you’re experiencing more than a few jitters and suspect caffeine intoxication, go to the emergency room immediately, Majlesi said. He explained doctors can use hemodialysis to filter out caffeine from the blood. If a person consumed large amounts of caffeine within one to two hours, Majlesi added that doctors may also dispense activated charcoal, which binds to caffeine and prevents it from getting absorbed in the gut.

Doctors will also administer medications to stabilize the patient and treat severe symptoms. For example, Majlesi said beta-blockers and benzodiazepines are often prescribed to treat neurological issues such as hallucinations and seizures.

How to avoid caffeine intoxication

Both Majlesi and Palinski-Wade advised monitoring how much caffeine you are consuming daily. Coffee is a popular source of caffeine, but products such as sodas, green tea and cacao can add to your caffeine intake.

Majlesi warned against energy drinks and caffeine powders because of the high caffeine concentrations. Both products are supplements and may also contain large amounts of sugar and other stimulants such as guarana.

Once you’ve decided on your caffeinated drink, Palinski-Wade advised to drink water throughout the day. Staying hydrated can help replenish water-soluble vitamins since caffeine is a diuretic.

Having food in your stomach — especially a meal high in protein and fiber — can also help by allowing the body to absorb caffeine over a longer period, Palinski-Wade said. “You might experience fewer side effects versus if you were having it on an empty stomach,” she added.

All in all, caffeine intoxication is preventable. The most important thing is to listen to your body and what it can tolerate, Palinski-Wade said. So, the next time you’re staring back at an empty mug, take a moment and see if you really need another refill or if you may be better served by a water break.

Jocelyn Solis-Moreira is a freelance health and science journalist based in New York.

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