Written by: Lana Adler
Updated March 10, 2021
Around 90% of American adults (1) drink some form of caffeine every day. There’s no doubt about it — it’s a popular stimulant. Caffeine can improve memory, concentration, and physical performance (2). However, too much caffeine can lead to uncomfortable and even dangerous side effects.
Many people know that caffeine appears in beverages like coffee, tea, and energy drinks, but it can also show up in less obvious places, like chocolate, soda, pain relievers (3), and other foods. Staying aware of your caffeine intake can be confusing, but it’s a vital step in knowing whether you’ve had too much.
How Much Caffeine Should You Have in a Day?
Most people can safely consume up to 400 milligrams of caffeine per day (4), and doses as low as 200 milligrams can produce the desired effects. That may not sound like much, but it can add up quickly depending on how often you visit your local coffee shop. The average person has 319 milligrams of caffeine (5) per day.
The following are a few examples of popular caffeinated beverages and the typical amount of caffeine they contain:
- An 8-ounce cup of brewed coffee can have 95 milligrams to 200 milligrams of caffeine.
- An 8-ounce cup of black tea can have 14 milligrams to 60 milligrams of caffeine.
- An 8-ounce energy drink can have 70 milligrams to 100 milligrams of caffeine.
- A 12-ounce can of soda may have 35 milligrams to 45 milligrams of caffeine.
- A 16-ounce coffee beverage can have up to 500 milligrams of caffeine.
Depending on the strength of your coffee, just two to four cups could hit the daily recommended caffeine intake — and that’s not accounting for any caffeine present in other foods or drinks that you consume. The line between just enough and too much caffeine can vary per person. In some people, doses of 500 milligrams, or about three to five 8-ounce cups of brewed coffee, can lead to symptoms like anxiety, shakiness, and increased heart rate.
What Are the Side Effects of Consuming Too Much Caffeine?
Common effects of safe caffeine consumption include an increase in energy, blood pressure, and a need to urinate. For some people, caffeine can also cause heartburn or an upset stomach.
Those are all normal effects of drinking or eating caffeine in safe amounts, below 400 milligrams. However, when you have too much caffeine, you may begin to experience unwanted side effects. These can include:
- Faster or irregular heartbeat
- Insomnia and difficulty sleeping
- Restlessness or shakiness
Can You Overdose on Caffeine?
Caffeine overdose can lead to death in rare cases. However, death from too much caffeine typically involves a medication that has caffeine as an ingredient, or when caffeine is mixed with drugs or alcohol.
Energy drink consumption, in particular, can increase your risk of caffeine overdose, whether you drink them daily or once in a while. Researchers have attributed a rise in caffeine-related visits to the emergency room to energy drinks and other highly concentrated caffeinated beverages.
How Can You Tell If You’ve Had Too Much Caffeine?
You may have had too much caffeine if you get a headache or start to feel jittery, anxious, or dizzy. Regularly consuming too much caffeine can also lead to dependency. You may find yourself needing to have more of it to maintain the same energy and performance benefits.
Prolonged caffeine use can also affect your vascular adenosine receptor system (6). Adenosine helps you fall asleep by binding to A1 receptors in your brain. Caffeine prevents that bond from happening, enabling you to stay awake and energized. The more often you have caffeine, especially in high amounts, the harder it is for your brain to counteract these effects and maintain a healthy sleep-wake cycle.
What Should You Do If You’ve Consumed Too Much Caffeine?
If you suspect that you’ve had too much caffeine, stop consuming it for the day. Drink water instead to stay hydrated. Caffeine is a diuretic and can dehydrate you. You can also eat something to slow the absorption of caffeine. If you’re feeling anxious, it may help to practice deep breathing, or go for a walk.
How Does Caffeine Impact Sleep?
Difficulty sleeping is a common side effect of having too much caffeine. People who regularly consume caffeine may have a tougher time falling asleep, wake up earlier than usual, and enjoy less restful sleep overall. Caffeine disrupts your sleep to varying extents, depending on how much you consumed, when you last had it, and your personal sensitivity to caffeine.
For example, having caffeine too close to bed can cause you to wake up during the night. One study found that people who had caffeine 3 hours before bed spent a total of 27 minutes awake during the night. Even those who last had caffeine 6 hours before bed found their sleep interrupted, spending a total of 8 minutes awake. Caffeine can also shorten your sleep by up to 30 minutes (7). Finally, caffeine can alter your sleep architecture, reducing the amount of time you spend in light and deep sleep.
Part of the varying effects can be attributed to what some researchers call a “coffee cycle." An estimated 90% of Americans drink coffee every day. Most of those people enjoy coffee during the daytime, followed by a period of caffeine withdrawal while they sleep. If they’re not careful about restoring their caffeine the following morning, they may experience the effects of sleep deprivation, which include decreased productivity, increased irritability, poor mood, and increased risk of work and car accidents. This, in turn, leads them to feel like they need caffeine to boost their energy, even though their reliance on caffeine may be exactly what’s sapping it.
The more caffeine you consume, the more havoc it may wreak on your sleep and energy levels. People who consume more caffeine are more likely to report having trouble sleeping at night (8) and staying awake (9) during the day.
How Long Should You Avoid Caffeine Before Bed?
Caffeine stays in your system for three to six hours. At a minimum, you’ll want to avoid having any for at least six hours before going to bed. However, since people’s sensitivity to caffeine can vary, some experts recommend avoiding caffeine for up to 11 hours before bedtime. For example, some studies have shown that caffeine consumed even six hours before bed can still disrupt sleep and shorten it by more than one hour.
Problematically, most people have caffeine within that time frame. Up to 90% of people consume caffeine between noon and 6 p.m., and nearly 70% consume it between 6 p.m. and midnight. Caffeine use later in the day is even more common among younger people, who are sensitive to caffeine. Over one-third report having their first caffeinated beverage of the day at 5 p.m. or later.
What Are Some Other Ways You Can Start Your Day Without Caffeine?
You can do plenty of things to boost your energy and focus in the morning without caffeine. For example, increasing your exposure to sunlight (10) will give you a natural energy boost and help reset your circadian rhythm. Pairing sunlight exposure with some morning exercise (11) outside can also help, whether it’s a walk or something more vigorous. You can also wake yourself up with energizing music, scents, and colors.
Because we have a cultural awareness of caffeine’s energy-boosting power, we expect it to improve our performance. However, some of those performance improvements may be due to a placebo effect. In one study, participants were given a dose of caffeine in the morning and a placebo 4 hours later. After the placebo, they continued to operate at peak cognitive performance (12) even though the effects of the initial caffeine dose had worn off.
Should You Avoid Caffeine?
Caffeine affects people in different ways. Some people may need several cups of coffee to feel alert, while one cup may cause side effects for others. However, people with the following conditions should take care to avoid caffeine as much as possible:
- Gastroesophageal reflux disease (GERD)
- Heart arrhythmias
- High blood pressure
Caffeine may also cause negative interactions with certain medications, including some antibiotics, and asthma and heart medications.
People who are pregnant or breastfeeding should also avoid caffeine, since caffeine can pass through the placenta or breast milk. The American Academy of Pediatrics recommends that children and adolescents avoid caffeine because of its effects on sleep and blood pressure (13). However, almost 75% of children (14) have caffeine daily. Soda, coffee, and energy drinks are the biggest culprits for childhood caffeine consumption.
Caffeine doses below the recommended maximum may be dangerous if you have a preexisting condition or take certain medications. If you are concerned about your caffeine intake, talk to your doctor.
What Are the Symptoms of Caffeine Withdrawal?
If you stop caffeine use abruptly, you may experience caffeine withdrawal, even if you’ve been staying within the daily recommended limits. Symptoms may include drowsiness, headaches, irritability, nausea, and trouble concentrating. Caffeine withdrawal can begin as soon as 12 hours after you last had it. However, symptoms usually go away on their own after a few days to a week.
If you decide to stop having caffeine, you may want to wean yourself off gradually to avoid the effects of caffeine withdrawal. Start by drinking one less cup of coffee a day, or switch to a less intense alternative like green tea, black tea, or decaffeinated coffee.
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- https://medlineplus.gov/caffeine.html Accessed on March 1, 2021.
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