Caffeine Overdose Symptoms and Potential Health Issues

When looking for a quick boost of energy, you may be tempted to reach for a caffeinated drink.

However, drinking too much caffeine can affect your health, and learning to watch for the signs of an overdose is essential for anyone who regularly consumes the substance.

Our guide helps you understand the dangers of a caffeine overdose, how to prevent it from happening, and what taking too much of the compound can do to your health.

The most common sources of caffeine are energy drinks, coffee, tea, and sodas.

While the health benefits of moderate and occasional intake are known, we also understand a great deal about the impact of chronic and habitual caffeine use, which may be damaging to your body.

Keep reading to learn more about the risks of too much caffeine, how to protect yourself from an overdose, and the best substitutes you can consume if you want more energy healthily.


Understanding Caffeine Overdose

Caffeine, while natural, is a potent drug that can stimulate your central nervous system.

It is, in fact, classified as a psychoactive drug, and its effects on your body include raising your heart rate, increasing your alertness, and changing the signals that allow your body and brain to communicate with each other.

While these effects can sometimes be meaningful, as we will discuss below, in large amounts, they can be dangerous.

Caffeine stays in your system for many hours, sometimes as many as six, and can affect different people differently; research provides conflicting information about the effect of caffeine on many body systems, including blood pressure, hormone balance, blood sugar, moods, and brain activity.

These varying data point to a great variability in how this drug affects each person who consumes it.


How Much Caffeine is Too Much?

Caffeine is naturally found in many beverages and added to others.

Common sources of caffeine include:

  • Many soft drinks
  • Tea, including black, green, and white varieties
  • Chocolate
  • Coffee, and all beverages containing coffee
  • Many over-the-counter stimulants designed to keep you awake
  • Many energy drinks
  • Some supplements and drugs designed to promote weight loss or performance enhancement

Most people get their caffeine from coffee, as this is the second most common beverage in the world, after water.

Drinking too much caffeine can cause irritability, nervousness, and sleep problems in many people.

In others, drinking too much can interfere with hormone regulation, and cause other health issues.

What qualifies as too much caffeine for one person may have no effect on someone else.

Your individual tolerance will dictate how the substance affects you, and how much you should consume.

When researching the health benefits of this drug, which we will discuss below, the maximum amount studied that seems to provide any benefit to the average person is 500 milligrams each day.

This is the equivalent of drinking about five cups of regular coffee that you brew at home.

However, most doctors agree that drinking more than 360 milligrams of caffeine per day exceeds a safe amount for the average person.

This is the same amount found in one medium (grande) Starbucks coffee.

If you are pregnant, your recommended daily allowance should not exceed 200 milligrams per day.

Those who are most likely to overdose on caffeine are not just everyday coffee drinkers, though.

You would have to drink a lot of coffee or very strong coffee to reach an overdose amount, but when you consume energy drinks, diet pills, and other supplements containing caffeine, your levels can rise significantly and quickly.

Those who are diagnosed with an overdose tend to be people trying to lose weight or stay awake, and they thus take too many substances containing the drug.

Whether you ever reach an “overdose” level of caffeine depends largely on you, individually.

Some people feel no symptoms after 500 milligrams, while others are clearly ill and need medical assistance at that dosage.

The Food and Drug Administration (FDA) considers consumption of over ten grams of caffeine per day for an adult to be a toxic dose.

That is the equivalent of between 50-100 cups of regular, home-brewed coffee.

So, by drinking coffee alone, it would be hard to overdose on caffeine.

But some beverages and supplements contain much more of this substance than a regular cup of coffee.

For example, here are the drug’s quantities in some common foods and drinks:

  • One Ten-Hour Energy Shot – 422 milligrams of caffeine
  • One 16-ounce iced coffee from McDonald’s – 200 milligrams of caffeine
  • One Five-Hour Energy Shot – 200 milligrams of caffeine
  • One 16-ounce Iced Espresso from Starbucks – 225 milligrams of caffeine
  • One Monster Energy Drink – 160 milligrams of caffeine
  • One serving of black tea, iced or hot – 55 milligrams of caffeine
  • 12 ounces of Mountain Dew soda – 55 milligrams of caffeine
  • One serving of chai tea – 47 milligrams of caffeine

Even 16 ounces of decaffeinated coffee from Starbucks still contains 25 milligrams of caffeine, which is equivalent to a serving of white, oolong, or jasmine tea.


Symptoms of a Caffeine Overdose

Caffeine intoxication, also known as caffeine overdose, is officially diagnosed when you are exhibiting five of the following symptoms (1):

  • Restlessness
  • Excitement
  • Nervousness
  • Showing a flushed face
  • Insomnia
  • Frequent urination
  • Muscle twitching
  • Digestive problems, including diarrhea or an upset stomach
  • Difficulty composing sensible thoughts or speech
  • Cardiac arrhythmia or tachycardia
  • Inability to become tired
  • Agitation

Even if you don’t reach this level of intoxication, you can still feel symptoms from consuming too much.

Other symptoms that may tell you that you have had too much caffeine include:

  • Difficulty breathing
  • Feeling hyper-alert or wired
  • Irritability
  • Fever
  • Feeling confused
  • Excessive thirst
  • Sweating
  • Racing or rapid heartbeat
  • Hallucinations
  • Fainting, or feeling dizzy

For some people, even a small amount of caffeine can cause negative effects, such as feeling nervous or experiencing headaches or the inability to sit still.

Those with a lower tolerance for this drug usually manifest anxiety, digestive disorders, decreased immunity, cardiac problems, or other illnesses that the substance can exacerbate (3).

Here are the most common health concerns either that caffeine consumption can cause or to which it can contribute.


Health Concerns Related to Caffeine Consumption


Heightened Anxiety

If you already experience anxiety or anxious thoughts, caffeine can worsen these symptoms.

Research suggests that anxiety is a natural biological response to this drug’s consumption in some people.

If you are already stressed, nervous, or otherwise feeling overwhelmed, too much of this substance can contribute to making you feel overly anxious; thus, you should avoid consuming caffeine and other stimulants, including sugar, to see if this helps your symptoms.

Those living with chronic stress, high levels of stress, or nervousness may feel the effects of caffeine more strongly and be more susceptible to an overdose, as well.

Researchers have found that people who have been diagnosed with General Anxiety Disorder (GAD), panic disorders, phobias, and other mental health issues experience the stimulant’s activity more than those without these diagnoses (4).

Caffeine can, therefore, exacerbate the symptoms of anxiety, including fear, nervousness, tremors, and other physical reactions to anxiety.

For those with these types of disorders, it would be suggested to avoid or limit caffeine intake.

It is important to remember that this substance is found in many products, not just coffee.

Energy drinks, tea, sodas, yerba maté, and other beverages also contain caffeine, as do many foods formulated for weight loss.

Even some pain medications contain the drug, so you should always read labels before purchasing.

Don’t think you are safe if you opt for a decaffeinated coffee, because this drink still will contain a small amount of caffeine.

Chocolate is another sometimes-overlooked source of the stimulant, so limit your consumption of this, as well.


Increased Dependency

Because it is a psychoactive drug, caffeine can be addictive.

When you drink or ingest it over a long period, you can build up a tolerance for the drug, which means you need to take more to have the same effect.

Anyone who regularly drinks coffee and suddenly is not able to get their daily dose knows what caffeine withdrawal can feel like.

Decreasing your intake gradually can thus be a better option than quitting cold turkey.

If you decrease your intake of or stop using caffeine altogether, you will likely experience withdrawal symptoms.

These can range from mild to serious, depending on your previous level of consumption.

The most common symptoms of caffeine withdrawal include a headache, irritability, difficulty concentrating, anxiety, changes in your appetite, fatigue, and digestive problems.

These will decrease over time, but the first few days can be difficult, as you try to wean your body off this addictive substance.

When you consume caffeine regularly, you will likely need more over time to give you the same amount of energy.

Your body and brain build up a tolerance for this drug, causing you to need more over time if you want the same results.

Using caffeine habitually to supply energy can mask other health problems, as well.


Sleep Disruptions

As a stimulant, caffeine naturally disrupts sleep.

If you have insomnia or other sleep-related disorders, consuming this drug can make your symptoms worse; additionally, it can cause changes to the hormones that regulate your body’s natural sleep-wake cycle, which can change how well you sleep or how long you are able to stay asleep.

When you have poor sleep, you tend to consume more caffeine to supply you with the needed energy, which in turn contributes to your inability to get a good night’s rest.

If caffeine is interfering with your ability to sleep well at night, there are several measures you can take.

You can eliminate your intake of the drug altogether.

If this seems too extreme a step, try cutting back on how much of it you take in, and do not consume anything with the substance afternoon each day.

Because it takes up to six hours for caffeine to leave your system, you want to leave plenty of time for your body’s natural sleep hormones to kick in.

If you are having trouble sleeping, often eliminating or cutting back on caffeine can help your problems quickly.

If you want to minimize withdrawal symptoms, though, be sure to lower your intake gradually.


Digestive Issues

Among the many reasons people drink coffee in the morning is to stimulate their bowels.

When you drink this beverage, it triggers the release of gastrin in your system, a hormone that speeds up colonic activity.

It may not necessarily be the caffeine that causes this, but we don’t know this at this time.

Caffeine does, however, stimulate peristalsis, which is the contractions in your digestive tract that move material through your system.

When taken in excess, though, this same stimulating effect may lead to diarrhea or loose stools in some.

If you suffer from a gastrointestinal disorder that makes you more likely to have diarrhea, caffeine can worsen your symptoms (5).

The same is true for those with gastroesophageal reflux disease, also known as GERD.

Those with GERD who consume caffeine are more likely to experience symptoms of their disorder, including heartburn, reflux, and other digestive problems (6).


Potential Elevation of Blood Pressure

Research on caffeine’s impact on blood pressure is unclear, but there is a reason for caution, especially in those who are already hypertensive.

Because it is a stimulant, it automatically should be used with caution by anyone whose blood pressure is consistently above normal; for others, the regular use of the drug could elevate an otherwise normal blood pressure, at least temporarily.

In a meta-analysis of research on caffeine and coffee consumption, it was noted that studies on caffeine intake show increased blood pressure levels fairly consistently, while coffee intake does not produce the same results (7).

This could be because coffee, in addition to containing caffeine, also provides beneficial antioxidants, which could mitigate the blood-pressure-raising effects of the caffeine.

Overall, a lot depends on your individual tolerance.

For many who consume caffeine regularly, when you build up a tolerance, you also may see less impact from it on your overall blood pressure levels.

Overall, the best advice is to watch your consumption, monitor how it makes you feel, and if you notice a significant change in your blood pressure, cut back or eliminate it in order to protect your heart.


Increased Heart Rate

Because it is a stimulant, high doses of caffeine can also increase your heart rate or worsen symptoms of arrhythmia.

Those who drink a lot of energy drinks have reported irregular heartbeat, known as atrial fibrillation (8).

Not everyone will experience this effect, though.

Even though with diagnosed heart issues don’t always see a change due to caffeine’s stimulating nature.

As with all things related to caffeine, the effects vary widely per person.

If you consume caffeine and notice a change in your heart rate or pattern, you should decrease your intake, or stop consuming it entirely to see if your heart irregularity resolves.

If not, you should talk with your doctor.


Dehydration and Nutrient Depletion

Caffeine is a natural diuretic, which means, if you consume it, you urinate more frequently.

While it would take a lot of it really to dehydrate you, drinking coffee is not as hydrating as water or other decaffeinated beverages.

Drinking coffee in the evening or at night can also cause you to need to urinate during the night, which may interrupt your sleep.

Further, caffeine can deplete your levels of essential nutrients, such as Vitamins B and C, calcium, zinc, magnesium, and potassium.

To avoid nutritional deficiencies, keep your intake low, and eat a healthy, well-balanced diet.


Hormone Imbalances

When you consume caffeine, it triggers your adrenal glands to produce epinephrine and norepinephrine.

Over time, this can lead to adrenal fatigue, especially in those living with high stress.

Caffeine can also contribute to higher levels of estradiol and testosterone, which can create potential problems and hormone imbalances in some people.


Increases Effects of Other Ingredients

Many caffeinated beverages not only contain the stimulant caffeine, but also are high in sugar, additives, and other ingredients that can produce negative health effects.

When combined, these ingredients can have an even more magnified impact than when they are consumed on their own.

When you consume high amounts of sugar, refined dairy, and other additives found in most coffee drinks or energy drinks, you are raising your levels of inflammation and blood sugar, and influencing other metabolic functions.

These, combined with the effects of caffeine, may cause major health problems.


The Good News about Caffeine in Moderation

After all the scary information about caffeine overdose, it may be hard to imagine that consuming smaller amounts of caffeine can be good for your health, but it is true.

A word of caution about these benefits, though.

Most research that shows benefits from this drug is based on the consumption of coffee, specifically, not caffeine in general, so you cannot apply these results to all forms of caffeine, in most cases.

Also, drinking caffeine daily will still lead to dependency and tolerance, so use with caution.

The following are known benefits of drinking coffee.


Reduce the Risk of Dementia

Researchers have discovered that people in their 40s and 50s who drink several cups of caffeinated coffee per day are less likely to develop Alzheimer’s and other forms of dementia in their 70s.

The reduction was by as much as 70 percent, marking a significant impact on age-related cognition (9).

Additional studies support this result, showing that drinking coffee regularly slows the rate of cognitive decline as we age.


Reduce the Risk of Suicide

As a stimulant that also impacts mood, coffee has the potential to lower your risk for suicide.

A 2013 study at Harvard confirmed that those who regularly drink coffee show a suicide rate of nearly one half of those who do not (10).


Decrease Risk for Stroke

Both older men and women can benefit from drinking a cup of coffee per day.

Three separate studies in Sweden confirmed that older men and women who drink coffee regularly experience as much as a one-quarter decreased risk for having a stroke (11, 12).



Caffeine is a stimulant that affects each of us differently.

In moderate to small doses, this drug, and its vehicle of coffee, in particular, can positively affect your health, but when you consume too much you may notice some negative effects.

Consuming too much caffeine can lead to problems such as insomnia, anxiety, high blood pressure, dependency on it, arrhythmia, dehydration, hormone imbalances, and digestive problems.

To avoid these, you should consume the substance in small doses, and avoid drinking caffeinated beverages daily.

Caffeine is an addictive drug.

If you want to stop using it, you should taper your consumption gradually, to avoid withdrawal symptoms.

Caffeine withdrawal can cause headaches, anxiety, irritability, and other uncomfortable symptoms, so be aware that quitting this drug abruptly can lead to such symptoms.

As each person reacts differently to caffeine, you should pay attention to its effect on your body and monitor this accordingly.

Some people show little tolerance for this stimulant, while others experience little or no impact from consuming it.

Always use your own health and symptoms as a guideline.

Some of the benefits of drinking coffee regularly include a reduction in the risk of stroke and suicide, as well as improvements in age-related cognition.

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