What Is a Caffeine Overdose?

Whether you’re a coffee lover, tea aficionado, or energy drink enthusiast, chances are you’ve had the caffeine jitters before. But there’s a difference between having the occasional one cup too many versus ingesting a dangerous dose. Find out how much caffeine is too much, hidden sources of caffeine, and symptoms of a caffeine overdose.

What Is Caffeine?

Caffeine is a compound found in the seeds, leaves, and fruits of various species of plants, and acts as a central nervous system stimulant when consumed. It works on various regions of the brain, both stimulating the autonomic nervous system as well as blocking the drowsiness-inducing actions of a molecule known as adenosine.

Caffeine is the most commonly consumed psychoactive drug of the methylxanthine class, with intakes from coffee alone averaging over 2.25 billion cups worldwide each day (1). Aside from coffee, other natural sources of caffeine include tea, cacao, kola nut, guayusa, and more. Caffeine is also synthetically produced, which is the most common form used in soft drinks, caffeine supplements, pain medication, and energy drinks.

An 8-ounce cup of black coffee typically contains approximately 95-165 milligrams (mg) of caffeine, but the caffeine content really depends on the type of bean, preparation method, and other factors. Average caffeine content of other common sources (2) includes:

  • Decaf coffee 12-15 mg
  • Black tea 25-48 mg
  • Green tea 25-29 mg
  • Soft drinks 24-46 mg
  • Energy drinks 27-164 mg
  • Hot chocolate 9 mg
  • Espresso (1 ounce) 47-64 mg
  • Energy shots (1 ounce) 30-450 mg
  • Caffeine supplements 30-400 mg
  • Pain medications 20-45 mg

Benefits and drawbacks of caffeine consumption are highly individualized, with differences in caffeine metabolism affecting the stimulatory effect caffeine has on one person versus the next.

There are countless studies showcasing the benefits and drawbacks of caffeine consumption, with some of the most beneficial pros being: enhanced alertness, cognition, recall, agility, improved physical ability, improved insulin response, and reduction in risks for imbalances regarding blood sugar, heart, and liver health.

Since caffeine has diuretic properties, excessive loss of fluids and electrolytes may result if consumed in large amounts. High caffeine intake has also been linked to increased heart rate, blood pressure, nausea, and vomiting. Additionally, being that caffeine is a drug, withdrawal symptoms may result in headache, lethargy, and altered mood (3).

How Much Caffeine Is Too Much?

The recommended daily intake of caffeine for a healthy adult is between 360-400 milligrams, which equates to about three to four cups of coffee per day. Pregnant and nursing women should consult with their doctors before consuming caffeine, however, approximately 200 milligrams or less may be suitable (4). The health benefits associated with caffeine consumption tap out at about 500 milligrams, with more than 10 cups per day showing negative health consequences (5).

Caffeine takes an average of 6 to 8 hours to be fully processed by the body, and therefore it is best to consume caffeinated products earlier, rather than later in the day to avoid restlessness.

According to the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders, caffeine intoxication occurs when any five of the following symptoms are present: diuresis, excitement, flushed face, gastrointestinal disturbance, inexhaustibility, insomnia, muscle twitching, nervousness, psychomotor agitation, rambling speech, restlessness, rambling flow of thought and speech, or tachycardia (5).

Outside of these symptoms, any intake of 10 grams (10,000 milligrams) or more has been established as the toxic dose. While there a few fatalities associated with caffeine overdose, health risks do exist in regards to high intakes. Anything above 500 milligrams may result in negative health consequences, including insomnia, rapid heart rate, uncontrolled muscle spasms, dehydration, nausea/vomiting, and more (5).

Since it would take anywhere between 50-100 cups of coffee to trigger a true overdose, concerns surrounding higher than recommended caffeine intakes primarily lie within the “hidden” sources of caffeine, outside of just coffee alone.

By drinking several cups of coffee per day, in addition to energy drinks, caffeinated teas, nutritional supplements, pain medications, diuretics, and foods with caffeine, an individual’s caffeine “bucket” can fill up without one realizing it. These are the most common cases where caffeine overdose is seen, as well as in those who are extremely sensitive to caffeine metabolism due to biological reasons (genetics, gender, medication interactions, etc). That is why it is important to become cognizant of the hidden sources of caffeine you may be consuming on a daily basis, just to err on the safe side and avoid any potential drawbacks.

Symptoms of a Caffeine Overdose

As previously noted, symptoms of caffeine overdose greatly vary from person to person. Underlying medical conditions, genetic/biological characteristics, weight, gender, and more can all affect one’s ability to breakdown caffeine, and therefore symptoms may range from mild to severe depending on the individual.

Mild symptoms, which should signal the individual to stop intake of any additional source of caffeine, include:

  • Anxiety
  • Frequent urination
  • Headache
  • Increased heartbeat
  • Increased thirst
  • Insomnia
  • Sweating

Severe symptoms, which require immediate medical attention, include:

  • Chest pain
  • Confusion
  • Convulsions
  • Dizziness
  • Fever
  • Hallucinations
  • Heart palpitations/irregular heartbeat
  • Muscle twitching
  • Nausea/vomiting

Symptoms act as the body’s warning system. If you think that you have over-consumed caffeine to the point that it will adversely affect your health, or are experiencing any symptom that is affecting your normal functions, it is always advised to seek immediate medical attention.

Treatment of caffeine overdose is similar to other poisoning cases, with activated charcoal often being administered to absorb excessive amounts of caffeine in the body. Additionally, laxatives or gastric lavage may be used if the caffeine has already made it into the GI tract, and monitoring of heart rate and breathing may be initiated.

Overdose of caffeine can be prevented by paying attention to the amount of caffeine you consume each day, understanding adverse interactions caffeine may have with medications or medical diagnoses, obtaining proper rest each night to avoid needs for exogenous stimulation, and opting for non-caffeinated alternatives (6).

Other Caffeine Risk Factors

In moderate amounts (under 400 milligrams/day), caffeine is generally recognized as safe. That being said, individual characteristics will determine the appropriate level of caffeine one can and should consume each day.  Therefore, it is always best to pay attention to how your body reacts.

Side effects of consuming high intakes on a regular basis include caffeine addiction, insomnia, irritability, withdrawal symptoms, increased stomach acid production, elevated blood pressure, and more.

Health risks associated with long-term high intakes of caffeine include decreased reproductive abilities, lowered birth weights in babies, sleep imbalances, GI issues/ulcers, issues surrounding bone metabolism, and increased risks surrounding cardiovascular and hepatic health (7).


Are you trying to reduce your caffeine intake? Let us know in the comments below!


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