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More than 400 milligrams (about 4 cups) of caffeine is too much. Drink lots of water, take a walk, practice deep breathing and wait it out. If you experience an irregular heartbeat or feel dizzy or faint after caffeine, go to the emergency room.
- Practice Deep Breathing
You might find it helpful to record yourself talking through...
- Practice Deep Breathing
Jun 7, 2024 · How much is too much caffeine? There are no guidelines in the UK specifically, but the European Food Safety Authority EFSA advises healthy people to drink no more than 400mg per day, and no more...
Aug 7, 2020 · The general rule of thumb is to stick to 200 mg of caffeine if you are a slow metabolizer (that's 2 cups of coffee) and consider taking up to 400 mg of caffeine if you are a fast metabolizer (equivalent to about 4 cups of coffee).
- Overview
- 1. Anxiety
- 2. Insomnia
- 3. Digestive issues
- 4. Muscle breakdown
- 5. Addiction
- 6. High blood pressure
- 7. Rapid heart rate
- 8. Fatigue
- 9. Frequent urination and urgency
Although caffeine is generally safe in low-to-moderate amounts, high levels of consumption can cause unpleasant and even dangerous side effects.
Coffee and tea are incredibly healthy beverages.
Most types contain caffeine, a substance that may boost your mood, metabolism and mental and physical performance (1, 2, 3).
Studies have also shown that it’s safe for most people when consumed in low-to-moderate amounts (4).
However, high doses of caffeine may have unpleasant and even dangerous side effects.
Research has shown that your genes have a major influence on your tolerance to it. Some can consume much more caffeine than others without experiencing negative effects (5, 6).
Caffeine is known to increase alertness.
It works by blocking the effects of adenosine, a brain chemical that makes you feel tired. At the same time, it triggers the release of adrenaline, the “fight-or-flight” hormone associated with increased energy (8).
However, at higher doses, these effects may become more pronounced, leading to anxiety and nervousness.
In fact, caffeine-induced anxiety disorder is one of four caffeine-related syndromes listed in the Diagnostic and Statistical Manual of Mental Disorders (DSM), which is published by the American Psychiatric Association.
Extremely high daily intakes of 1,000 mg or more per day have been reported to cause nervousness, jitteriness and similar symptoms in most people, whereas even a moderate intake may lead to similar effects in caffeine-sensitive individuals (9, 10).
Additionally, modest doses have been shown to cause rapid breathing and increase stress levels when consumed in one sitting (11, 12).
Caffeine’s ability to help people stay awake is one of its most prized qualities.
On the other hand, too much caffeine can make it difficult to get enough restorative sleep.
Studies have found that higher caffeine intake appears to increase the amount of time it takes to fall asleep. It may also decrease total sleeping time, especially in the elderly (13, 14).
By contrast, low or moderate amounts of caffeine don’t seem to affect sleep very much in people considered “good sleepers,” or even those with self-reported insomnia (15).
You may not realize that too much caffeine is interfering with your sleep if you underestimate the amount of caffeine you’re taking in.
Although coffee and tea are the most concentrated sources of caffeine, it is also found in soda, cocoa, energy drinks and several types of medication.
Many people find that a morning cup of coffee helps get their bowels moving.
Coffee’s laxative effect has been attributed to the release of gastrin, a hormone the stomach produces that speeds up activity in the colon. What’s more, decaffeinated coffee has been shown to produce a similar response (19, 20, 21).
Given this effect, it’s not surprising that large doses of caffeine may lead to loose stools or even diarrhea in some people.
Although for many years coffee was believed to cause stomach ulcers, a large study of more than 8,000 people didn’t find any link between the two (22).
On the other hand, some studies suggest that caffeinated beverages may worsen gastroesophageal reflux disease (GERD) in some people. This seems to be especially true of coffee (23, 24, 25).
In a small study, when five healthy adults drank caffeinated water, they experienced a relaxation of the muscle that keeps stomach contents from moving up into the throat — the hallmark of GERD (25).
Rhabdomyolysis is a very serious condition in which damaged muscle fibers enter the bloodstream, leading to kidney failure and other problems.
Common causes of rhabdomyolysis include trauma, infection, drug abuse, muscle strain and bites from poisonous snakes or insects.
In addition, there have been several reports of rhabdomyolysis related to excessive caffeine intake, although this is relatively rare (26, 27, 28, 29).
In one case, a woman developed nausea, vomiting and dark urine after drinking 32 ounces (1 liter) of coffee containing roughly 565 mg of caffeine. Fortunately, she recovered after being treated with medication and fluids (29).
Importantly, this is a large dosage of caffeine to consume within a short period of time, especially for someone who isn’t used to it or is highly sensitive to its effects.
In order to reduce the risk of rhabdomyolysis, it’s best to limit your intake to about 400 mg of caffeine per day, unless you’re used to consuming more.
Despite all of caffeine’s health benefits, there’s no denying that it may become habit-forming.
A detailed review suggests that although caffeine triggers certain brain chemicals similarly to the way cocaine and amphetamines do, it does not cause classic addiction the way these drugs do (30).
However, it may lead to psychological or physical dependency, especially at high dosages.
In one study, 16 people who typically consumed high, moderate or no caffeine took part in a word test after going without caffeine overnight. Only high caffeine users showed a bias for caffeine-related words and had strong caffeine cravings (31).
Additionally, the frequency of caffeine intake seems to play a role in dependency.
In another study, 213 caffeine users completed questionnaires after going 16 hours without consuming it. Daily users had greater increases in headaches, fatigue and other withdrawal symptoms than non-daily users (32).
Overall, caffeine doesn’t seem to increase the risk of heart disease or stroke in most people.
However, it has been shown to raise blood pressure in several studies due to its stimulatory effect on the nervous system (33, 34, 35, 36).
Elevated blood pressure is a risk factor for heart attack and stroke because it may damage arteries over time, restricting the flow of blood to your heart and brain.
Fortunately, caffeine’s effect on blood pressure seems to be temporary. Also, it seems to have the strongest impact on people who aren’t used to consuming it. (35, 36)
High caffeine intake has also been shown to raise blood pressure during exercise in healthy people, as well as in those with mildly elevated blood pressure (37, 38).
Therefore, paying attention to the dosage and timing of caffeine is important, especially if you already have high blood pressure.
The stimulatory effects of high caffeine intake may cause your heart to beat faster.
It may also lead to altered heartbeat rhythm, called atrial fibrillation, which has been reported in young people who consumed energy drinks containing extremely high doses of caffeine (39).
In one case study, a woman who took a massive dose of caffeine powder and tablets in an attempted suicide developed a very rapid heart rate, kidney failure and other serious health issues (40).
However, this effect doesn’t seem to occur in everyone. Indeed, even some people with heart problems may be able to tolerate large amounts of caffeine without any adverse effects.
In one controlled study, when 51 heart failure patients consumed 100 mg of caffeine per hour for five hours, their heart rates and rhythms remained normal (41).
Regardless of the mixed study results, if you notice any changes in your heart rate or rhythm after drinking caffeinated beverages, consider decreasing your intake.
Coffee, tea and other caffeinated beverages are known to boost energy levels.
However, they can also have the opposite effect by leading to rebound fatigue after the caffeine leaves your system.
One review of 41 studies found that although caffeinated energy drinks increased alertness and improved mood for several hours, participants were often more tired than usual the following day (42).
To maximize caffeine’s benefits on energy and avoid rebound fatigue, consume it in moderate rather than high doses.
Summary
Although caffeine provides energy, it can indirectly lead to fatigue when its effects wear off. Aim for moderate caffeine intake to help minimize rebound fatigue.
Increased urination is a common side effect of high caffeine intake due to the compound’s stimulatory effects on the bladder.
You may have noticed that you need to urinate frequently when you drink more coffee or tea than usual.
Most research looking at the compound’s effects on urinary frequency has focused on older people and those with overactive bladders or incontinence (43, 44, 45).
In one study, 12 young to middle-aged people with overactive bladders who consumed 2 mg of caffeine per pound (4.5 mg per kilogram) of body weight daily experienced significant increases in urinary frequency and urgency (44).
For someone weighing 150 pounds (68 kg), this would equate to about 300 mg of caffeine per day.
In addition, high intake may increase the likelihood of developing incontinence in people with healthy bladders.
- Franziska Spritzler
Oct 16, 2020 · How to counteract caffeine. The best way to deal with too much caffeine, unfortunately, is to just wait it out, integrative medicine doctor Bindiya Gandhi, M.D., tells mbg. According to one study, it can take anywhere from three to 10 hours for caffeine to fully flush out 1 of someone's system.
May 11, 2023 · Dehydration and fatigue. Once the caffeine leaves your system, you can experience an energy slump, as the NHS explains. Caffeine also stimulates the bladder, so increased urination is a...
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Mar 19, 2020 · Common signs of a caffeine crash include headaches, tiredness, difficulty concentrating, and irritability. This can be caused by lack of sleep or drinking too much coffee.
