How Much Caffeine Is Too Much?

Whether your go-to is tea or coffee, it's important to know what "too much caffeine" really entails.

Repeated cup of coffee on pink background
Photo: Getty Images/Yulia Reznikov

To some, "but first, coffee" isn't just a trendy turn of phrase; it's a motto to live by. And while caffeine, in general, has been linked to a number of health benefits—from improved exercise performance to boosted brainpower—it is possible to have too much caffeine.

Refresher: Caffeine is a stimulant, meaning it triggers activity in your central nervous system that can lead to increases in heart rate and blood pressure, among other side effects, according to the National Library of Medicine.

Caffeine also blocks adenosine receptors, aka central nervous system depressants in the brain that, normally, make you feel tired and induce sleep, says Robert Glatter, M.D., an assistant professor of emergency medicine at Lenox Hill Hospital, Northwell Health. By blocking them, caffeine wakes you up (and gives you that I-can-do-anything superhuman feeling), he explains.

Another interesting effect of caffeine: It increases the amount of the feel-good neurotransmitter, dopamine in your brain by slowing the rate at which dopamine is absorbed back into the rest of your body, explains Dr. Glatter—meaning caffeine can lead to a (short-lived) mood boost.

This all sounds great on paper, but too much of a good thing can be a bad thing. And, unfortunately, you can have too much caffeine. Here's what that looks like IRL—and how to stay mindful of your own caffeine consumption.

How much caffeine is too much?

It depends. The amount of caffeine your body can handle per day can vary based on a number of different factors, including whether you have a pre-existing sensitivity to caffeine, are pregnant, or have ongoing insomnia or anxiety, among other health conditions, says Niket Sonpal, M.D., a New York-based internist, gastroenterologist, and adjunct professor at Touro College. Other details such as age, weight, overall health, and genetics can also play a role, adds Dr. Glatter.

That said, on average, a healthy adult can consume 400 milligrams of caffeine per day (about four or five cups of coffee, roughly three to five energy drinks, or about 11 caffeinated soft drinks) without "dangerous, negative effects," according to the Food and Drug Administration (FDA). To reiterate, that's 400 milligrams total, not per source. So, when questioning whether you've had too much caffeine, focus on your collective caffeine intake, not just how much caffeine you're getting from individual sources such as coffee, tea, energy drinks—even chocolate. (

"You may think you aren't having much caffeine if you only have one cup of tea per day, but if you are also getting caffeine from a supplement and the foods you eat, you may be having too much overall," notes Erin Palinski-Wade, R.D.

What are the side effects of too much caffeine?

Caffeine—whether you're having a little or a lot of it—can have both short- and long-term effects on the body. Short-term effects usually begin between five and 30 minutes after consuming caffeine, says Dr. Sonpal. "Someone who consumes 40 mg of caffeine [roughly the amount in a 12-ounce can of a caffeinated soft drink] will have 20 mg remaining in their system after five hours," he explains. That's why having caffeine late in the day can wreck your sleep; it can take as long as five hours until the effects begin to wear off.

Overall, these are the most common side effects of too much caffeine:

Short-Term Effects:

  • Headaches
  • Upset stomach
  • Boost of energy
  • Improved alertness
  • Heartburn
  • High blood pressure

Long-Term Effects:

  • Restlessness
  • Anxiety
  • Insomnia
  • Increased urination
  • Rapid or abnormal heart rhythm
  • Irritability
  • Dependency

Can you overdose on caffeine?

On April 26, 2017, 16-year-old Davis Allen Cripe collapsed and died in his high school classroom of caffeine-induced cardiac arrest. Prior to his death, Cripe drank a large Mountain Dew, a latte from McDonald's, and an energy drink, all within a two-hour time period.

As tragic and terrifying as Cripe's death was, experts ensure that while you can technically overdose on caffeine, it's highly unlikely that you will.

"Research has shown that some people are slow metabolizers of caffeine, and their risk of cardiac events would be expected to go up the more caffeine they have," cardiologist Monali Y. Desai, M.D. previously told Shape. "That being said, the average person doesn't need to be concerned with drinking caffeine too quickly unless they're drinking 600 mg or more of caffeine every day or they're concerned they're a slow metabolizer." The key is to know your limits, stay within them, and if you know of any family history of abnormal heart rhythms, speak to a cardiologist about how much caffeine you should actually be consuming, suggested Dr. Desai. She also recommended speaking with a gastroenterologist about how your body digests and absorbs the stimulant if you're concerned about consuming too much caffeine, she added.

To that point, Cripe's autopsy showed no evidence of underlying cardiovascular or other health conditions. The medical examiner concluded that his death was likely caused by consuming too much caffeine in a short amount of time. So, not only should you be aware of how much caffeine you're consuming, but also the timeframe in which you're consuming it, particularly if you're concerned about how your body metabolizes caffeine, and if your intake is nearing or exceeding the FDA's recommendations. Jennifer Haythe, M.D., a cardiologist, assistant professor of medicine at Columbia University, and co-director of the Center for Women's Cardiovascular Health suggested spacing out all caffeinated drinks by one to two hours.

If you do happen to drink too much caffeine in a short time window, watch for symptoms such as heart palpitations, dizziness, lightheadedness, shortness of breath, and chest pain, said Dr. Haythe. "If you develop any of these signs, seek medical attention as soon as possible," she said.

Also important: The sources of your caffeine, as some are much more concentrated than others. For example, caffeine powders are so highly concentrated that, in some cases, a single teaspoon of pure, powdered caffeine can contain 3,200 mg of the stimulant—or about 20 to 28 cups of coffee, according to the FDA. The agency has recently been cracking down on companies that sell these caffeine powders in bulk quantities online.

How can you cut back if you're consuming too much caffeine?

If you regularly drink too much caffeine, you run the risk of experiencing not only the aforementioned short- and long-term side effects, but also caffeine withdrawal symptoms—such as headaches, irritability, and lack of concentration—whenever you abruptly fall below your usual intake, according to the Mayo Clinic.

In other words, it may be extremely common to consume caffeine on the reg, but it's still technically a drug—meaning you can become addicted to it, says Dr. Sonpal.

The good news is, you can wean yourself off caffeine. The key is to do so in small doses. For example, Palinski-Wade suggests cutting back by 50 mg (think: an 8-ounce cup of caffeinated green or black tea) each week until you're consuming under 400 mg of caffeine total per day. Switching to decaf coffee and caffeine-free teas can be super helpful in managing the habit, suggests Dr. Glatter.

He also recommends cutting back on brewing time for caffeinated coffee and tea. Why? The longer you steep coffee grounds, tea leaves, or tea bags in hot water, the higher the caffeine levels. Granted, it can be tough to control brewing time with most automated drip coffee makers (though some do have settings that allow you to customize brewing time and speed), but a French press or immersion brewer can offer a simpler way to reduce brew time.

Also: Don't forget to stay well-hydrated throughout your transition, since cutting back on caffeinated drinks may translate to drinking fewer liquids overall, adds Dr. Glatter.

Whatever route you choose, be mindful of any caffeine withdrawal symptoms you might experience. These symptoms are usually manageable, but if they begin to feel especially concerning or disruptive to your everyday life, remember you can always touch base with your doctor about what the best approach is for you.

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