How Your Body Tells You That You’re Consuming *Too Much* Caffeine

Photo: Stocksy / Pietro Karras
If you're among the 62 percent of Americans who start their day with a cup (or two) of joe, listen up. Coffee is comforting and flavorful, and the 96 milligrams of caffeine in each cup is an energizing, often steadfast part of one's morning routine (especially if you're dealing with the fog of seasonal allergies). It's one of the most beloved beverages around (that's kept civilizations going for centuries, and made even easier access to thanks to our beloved at-home coffee makers).

But how much caffeine is too much caffeine?

What is caffeine, anyway?

According to the Alcohol and Drug Foundation, "caffeine is a stimulant drug, which means it speeds up the messages traveling between the brain and the body." It works by increasing energy production in the central nervous system, in muscles and, in general, increases metabolic rate. In moderation, it can help boost ones mood and mental and physical performance, explains Erika Schwartz, MD, a New York City-based physician, founder of Evolved Science, and a New York Times best-selling author. Caffeine is most commonly found in "coffee, black tea, sodas, energy drinks, and even chocolate."

Experts In This Article

How much caffeine is considered safe in a day?

Up to 400 milligrams of caffeine per day (about four or five eight-ounce cups of coffee or two energy drinks) is considered safe for most adults, according to Dr. Schwartz, but each person's sensitivity to the substance varies, and your body will warn you with signs when enough turns out to be too much, so it's important to take note. Below, see some of the telltale signs that you are consuming too much caffeine.

What happens when you consume too much caffeine

1. Increased anxiety

Ever feel like you're on the verge of having a panic attack after you've consumed a double shot of espresso? Indeed, drinking too much caffeine can oftentimes mimic, or even trigger, anxiety symptoms. "When you consume too much caffeine, your blood pressure rises," says Dr. Schwartz. This can cause feelings of anxiety, nervousness, jitters, and a faster heart rate. Because caffeine speeds your central nervous system, it may trigger an increased release of adrenaline that can make you jumpy or scared, and potentially worsen your pre-existing anxiety symptoms.

2. Trouble sleeping

Because of its impact on the central nervous system, caffeine can keep you from falling asleep, staying asleep, or reaching a deep REM state. Since it takes an average of five to six hours for half of the caffeine you consume to be eliminated from your body and about a day for it to completely clear your system, it's better to consume a moderate amount of caffeine early in the day to ensure a restful night.

That said, if you need a jolt of caffeine, but want to still be able to get a good night's rest, sleep experts often recommend beverages that contain L-theanine, a compound primarily found in green tea which can potentially help your brain relax by reducing stress-related hormones and neuron excitement (when consumed hours before bedtime).

3. Digestion irritation

Due to the high acidic content of the beverage and its laxative properties, coffee (and the caffeine in it) can also heavily impact your gut. This can lead to additional digestion-related symptoms such as heartburn, cramping, indigestion, nausea, and diarrhea, to name a few.

Of course, for most folks, it's no secret that a cup of hot coffee can make you poop. Will Bulsiewicz, MD, a board-certified gastroenterologist and the author of Fiber Fueled, tells Well+Good that this is due to heightened stimulation of the colon, which keeps things moving along in your digestive tract. “The reason this happens is that both regular and decaffeinated coffee increase the activity of the colon, leading to more pressure waves,” he says.

4. Frequent urination

Caffeine can act as a mild diuretic, which means that it can cause dehydration. If you're having a cup of coffee, Dr. Schwartz suggests eating a snack beforehand or with the beverage to slow the fluid's movement through your body. Keep in mind hydration and digestive function go hand in hand. As such, it's important to stay well-hydrated, especially when you've had one too many cups of coffee. Remember that dehydration is also associated with many other negative health outcomes and side effects, including joint pain, muscle cramps, compromised skin health, decreased immunity, and decreased cognitive function.

5. Headaches

While moderate caffeine consumption can sometimes help relieve a headache (it's a common ingredient in many over-the-counter headache medications), extreme consumption can result in lasting headaches—one of the common signs of drinking too much coffee regularly.

How does the caffeine content in coffee compare to tea or soda?

According to Dr. Schwartz, if you feel yourself experiencing any of the symptoms above, there are ways to limit your caffeine intake slowly to suppress or avoid feeling withdrawal repercussions. She suggests "swapping a cup of coffee with a caffeine-free tea," (or one with less caffeine at first), opting for decaf later in the day, and logging your daily consumption so you can keep track of where and when any troubles arise. Keep in mind, however, how much caffeine there is in decaf coffee. Although minimal, there's still some trace amounts in it.

Of course, if going cold turkey on caffeine isn't an option, you can always try other lower caffeine drinks, such as tea or soda. For context, most popular carbonated drinks that contain caffeine range from 33 to 55 milligrams per 12-ounce can. Meanwhile, black tea contains the highest amount of caffeine, ranging between 64 and 112 milligrams milligrams, green tea ranges between 24 to 39 milligrams, and white tea is between 32 and 37 milligrams, per eight-ounce serving.

Matcha, on the other hand, has about 19 to 44 milligrams of caffeine per gram of tea (it's recommended to use about two grams of matcha for an eight-ounce cup). And decaffeinated teas will typically have less than 12 grams per eight-ounce serving. Herbal teas, on the other hand, won't have caffeine.

What to do if you've had too much caffeine

POV: You've already had excessive amounts of coffee for the day, and you're in the midst of a jittery downhill spiral. What can you do, you may be wondering at this point? Registered dietitian Melissa Nieves, RD says there's unfortunately not much you can do to counteract coffee overdoses. "There's not much to do once caffeine is in your body except wait for it to be metabolized," Nieves says. Although the best way to rid yourself of too much caffeine is by simply waiting it out, the dietitian shared a few tips to help soothe some of the symptoms you're experiencing, and potentially expedite the process.

This includes:

  • Drinking water, which can help replenish any fluids lost while drinking excessive amounts of caffeine (due to its diuretic effects)
  • Going for a walk, which can help stabilize the jitteriness while boosting digestion and brain health
  • Practicing breathing exercises to help regulate the body and lower anxiety
  • Engaging in meditation to help reduce stress

Of course, when in doubt or if you suspect that you may have an intolerance or sensitivity to caffeinated drinks, it may be best to avoid these beverages or limit them. In fact, one of the caffeine habits of some of the longest-living people in the world is diluting coffee (ideally with water rather than sugary creamers), which can help stretch out the length of time that it takes all of the stimulating effects to hit your system.

(And on that note... how long does coffee creamer last?)

The benefits of drinking coffee (in moderation), explained by a dietitian:


Well+Good articles reference scientific, reliable, recent, robust studies to back up the information we share. You can trust us along your wellness journey.
  1. Rao, Theertham P et al. “In Search of a Safe Natural Sleep Aid.” Journal of the American College of Nutrition vol. 34,5 (2015): 436-47. doi:10.1080/07315724.2014.926153
  2. Nehlig, Astrid. “Effects of Coffee on the Gastro-Intestinal Tract: A Narrative Review and Literature Update.” Nutrients vol. 14,2 399. 17 Jan. 2022, doi:10.3390/nu14020399
  3. Chou, K-H, and L N Bell. “Caffeine content of prepackaged national-brand and private-label carbonated beverages.” Journal of food science vol. 72,6 (2007): C337-42. doi:10.1111/j.1750-3841.2007.00414.x

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