Caffeine: How Much Is Too Much?

Many coffee drinkers enjoy their morning cup of joe.

Some also enjoy a mid-morning coffee. And maybe an afternoon espresso.

So how much is too much?

If you have too much caffeine, you can experience negative side effects.

These include anxiety, restlessness, sleep disruptions, and heart problems such as palpitations.

In general, keeping caffeine intake between 400 and 600 milligrams per day is not linked with side effects in most people.

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How much caffeine is too much?

A study was done where participants were consuming 400 milligrams or more of caffeine per day. Researchers found that these participants were statistically significantly twice as high risk for five different symptoms. These included the following:

  • Headaches (tension-type or migraine headache)

  • Panic or terror spells

  • A feeling of being caught or trapped

  • Over worrying

  • Feelings of worthlessness

The Food and Drug Administration says that 400 milligrams per day is a safe amount for healthy adults. This shouldn’t lead to negative side effects. To give you an idea of what 400 milligrams is, it is about four or five eight-ounce cups of brewed coffee. Or it’s about five shots of espresso. In terms of energy drinks, that’s about two tops.

If you go over this amount of caffeine content, you will be more likely to experience negative side effects. Drinking coffee and tea in moderate amounts can have great benefits. This includes preventing certain chronic diseases, such as cancer, diabetes, liver disease, and cardiovascular disease.

Caffeine is helpful with cognitive function, athletic abilities, and energy levels. It can improve response time and exercise performance. Since caffeine improves concentration and accuracy, it can also enhance physical as well as mental tasks. Research shows that caffeine intake is potentially related to weight loss too.

9 side effects of too much caffeine

Depending upon the dose, caffeine can cause harmful side effects. This is why it’s essential to keep an eye on your caffeine intake. Be aware of the different foods and beverages that contain caffeine. Don’t forget that it’s not just tea and coffee that contains caffeine. Soft drinks and energy drinks contain caffeine as well. There are also some foods and dietary supplements that contain caffeine. Chocolate, candies, and some chewing gums contain caffeine as well. It’s also important to take a look at the caffeine content of your medications. For example, some over-the-counter pain relievers such as Excedrin also contain caffeine.

Increases heart rate

If you have excess caffeine, you are more susceptible to heart palpitations. This is especially true if you have any underlying medical conditions. Since caffeine has stimulant properties, it can increase your heart rate.

Increases blood pressure

For the average person, caffeine doesn’t increase the risk of heart disease or stroke. But since caffeine does have stimulant properties, it can raise blood pressure.

High blood pressure is a risk factor for heart attack and stroke. This is because having high blood pressure can lead to blood vessel damage over time. This can restrict blood flow to your heart and brain over time.

The good news is that caffeine’s effects on blood pressure appear to be temporary in nature.

Muscle breakdown

There is a rare condition called rhabdomyolysis. This is a very serious condition where damaged muscle fibers enter the bloodstream. This can lead to kidney failure, as well as other problems. Causes of rhabdomyolysis include trauma, muscle strain, snake bites, infection, and drug abuse. However, there have been several reports saying that excessive caffeine intake can lead to rhabdomyolysis.

In one example, a woman drank 565 milligrams of caffeine and then developed nausea, vomiting, and dark urine. She was able to recover after medication treatment and fluid intake. 565 milligrams is a large dose for someone who is not used to coffee consumption to have in a short period of time. This is why it’s important to limit your caffeine intake to less than 250 milligrams per day unless you are used to having more than this.

Frequent urination and incontinence

You may have noticed yourself that high caffeine intake can lead to higher urination frequency. This is because caffeine has stimulatory effects on the bladder. One study looked at 12 people with overactive bladders. They consumed two milligrams of caffeine per pound of body weight per day. They experienced significant increases in urinary frequency and urgency.


Caffeine can potentially become habit-forming. One research review said that even though caffeine may trigger brain chemicals in a similar way to cocaine or amphetamines, it doesn’t cause addiction in the same way.

But at high doses, it can lead to physical or psychological dependency. One study looked at 16 people who regularly consumed either no caffeine, moderate caffeine, or high caffeine levels. They performed a word test after going without caffeine. Results showed that high caffeine users had a bias towards caffeine-related words and had strong caffeine cravings. The other groups did not.

The frequency of caffeine intake appears to play a role in dependency. In another study, 213 caffeine users went 16 hours without added caffeine. They then filled out a questionnaire. Daily caffeine drinkers had more headaches, fatigue, and other caffeine withdrawal symptoms compared to others.

Although caffeine may not be an addiction, it certainly has the potential for dependency.


Of course, caffeine boosts your energy levels. However, it can have the opposite effect as well. This is because of rebound fatigue. Once the caffeine leaves your body, it can make you feel even more tired.

One research review looked at 41 studies. They found that even though caffeinated energy drinks increased alertness for several hours, participants were more tired the following day.

So how do you avoid this? You can continue to drink caffeine throughout the day. The downside of this is that it can affect your ability to sleep.

Upset stomach

Coffee can lead to diarrhea, heartburn, and indigestion. Coffee also has laxative effects. This is because coffee leads to the release of gastrin. Gastrin is a hormone that the stomach produces to speed up the activity of the colon. Even decaf coffee seems to produce the same response.

Caffeine itself can stimulate bowel movements by increasing peristalsis. Peristalsis is the contractions in your gastrointestinal tract that help to move food through. This is why large doses of caffeine can lead to loose stools or diarrhea in some people.

Studies show that caffeine can make acid reflux worse in some people. This is especially true for coffee in particular. One small study looked at five healthy adults. They drank a caffeinated beverage. Upon doing so, their lower esophageal sphincter relaxed. This helps to keep the contents of the stomach from coming upwards into the esophagus.


High caffeine intake can make it hard to get sufficient amounts of restorative sleep. Studies show that higher caffeine intake increases the amount of time it takes to fall asleep. Caffeine can also decrease total sleeping time. This is especially true in the elderly population.

The amount of caffeine you’re able to consume without affecting your sleep will depend upon your genetics as well as some other factors. It takes anywhere from 90 minutes to nine hours for caffeine to leave your system. This is why if you consume caffeine later in the day, you may negatively impact your sleep.

In one study, researchers gave 12 healthy adults 400 milligrams of caffeine either at bedtime, three hours before, or six hours before. The amount of time to fall asleep and the amount of time spent awake went up significantly. Researchers concluded that it’s important to monitor the amount and timing of caffeine to optimize your sleep.

Mood disturbances

Too much caffeine can actually lead to certain symptoms similar to those of mental illness. Caffeine overconsumption can lead to the following mood-related symptoms:

  • Terror or panic spells

  • Feeling of being caught or trapped

  • Over worrying

  • Having feelings of worthlessness

  • Anxiety

  • Nervousness

  • Jumpy, feeling alarmed (this is called the jitters)

  • Irritability

These symptoms can happen in part because caffeine blocks the effects of adenosine. Adenosine is a brain chemical that makes you feel tired. Caffeine also triggers the release of adrenaline, which is your “fight or flight” hormone. At higher doses of caffeine, these effects can be more pronounced, leading to anxiety and nervousness.

Caffeine-induced anxiety disorder is actually one of the four caffeine-related syndromes in the Diagnostic and Statistical Manual of Mental Disorders (the DSM). This is a publication from the American Psychiatric Association.

Extreme caffeine intake above 1000 milligrams can cause nervousness and jitters in most people. Even just a moderate caffeine intake can cause these symptoms in people who have caffeine sensitivity or low caffeine tolerance.

One study looked at 25 healthy men. They found that the men who drank 300 milligrams of caffeine had more than double the stress levels of those who took a placebo. The effects were similar between those who drank coffee regularly and those who did not.

Caffeine overdose

You can avoid caffeine overdose symptoms by staying within the recommended limit of 400 milligrams per day. According to the Food and Drug Administration, the dangerous effects of caffeine intoxication can happen at a dose of 1200 milligrams in one day. Be wary of pure caffeine powders and caffeine pills that deliver a high dose of caffeine quickly. Look out for certain workout dietary supplements that may contain high amounts of caffeine as well.

In general, unpleasant side effects of too much caffeine can resolve on their own. This usually happens after four to six hours. However, if you have irregular heartbeat, dizziness, or feel faint, then it’s a good idea to call your doctor or go to the emergency room.

If you feel like you’ve had a bit too much caffeine, drink lots of water and electrolytes. This is especially important if you are having diarrhea or vomiting. Do some deep breathing and go for a walk. This can help to burn extra energy and help to manage the anxiety that may come with too much caffeine.

Please note that it is also important to minimize your caffeine intake if you are pregnant. This is because pregnant women who consume more than 200 milligrams of caffeine per day may increase their risk of miscarriage.

Tips for reducing caffeine intake

You may not want to quit caffeine cold turkey since this can lead to withdrawal symptoms.

One good way to ease into kicking your caffeine habit is to mix caffeinated drinks with decaf versions.

Instead of coffee, why don’t you try switching to tea? Or switch from caffeinated coffee to decaffeinated coffee. If that seems too hard to start off with, then you can try alternating between decaf coffee and regular coffee every other day.

Don’t just think about cutting out coffee, though. Keep in mind that soft drinks and energy drinks often contain caffeine too. You may want to consider cutting back on these as well.

Try changing to herbal teas like yerba mate or chicory root. Keep track of how much caffeine you’re consuming. This can help you to make a plan as you eventually cut back.

As you can see, not all caffeine intake is bad. In fact, caffeine can have beneficial effects on your health. It’s all about knowing what your body can handle and keeping caffeine intake moderate.


  1. Jahrami, H; Al-Mutarid, M; Penson, PE; Faris, MA; Saif, Z & Hammad, L. (2020). Intake of caffeine and its association with physical and mental health status among University students in Bahrain. Foods. 9 (4), 473.
  2.  McKim, EM & McKim, WA. (1993). Caffeine: how much is too much?. Can Nurse. 89 (11), 19-22.

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