Caffeine: How much is too much?
Medically reviewed on March 8, 2017
If you rely on caffeine to wake you up and keep you going, you aren't alone. Caffeine is used daily by millions of people to increase wakefulness, alleviate fatigue, and improve concentration and focus.
How much is too much?
Up to 400 milligrams (mg) of caffeine a day appears to be safe for most healthy adults. That's roughly the amount of caffeine in four cups of brewed coffee, 10 cans of cola or two "energy shot" drinks. Keep in mind that the actual caffeine content in beverages varies widely, especially among energy drinks.
Although caffeine use may be safe for adults, it's not a good idea for children. Adolescents should limit caffeine consumption. Avoid mixing caffeine with other substances, such as alcohol.
Even among adults, heavy caffeine use can cause unpleasant side effects. And caffeine may not be a good choice for people who are highly sensitive to its effects or who take certain medications.
Women who are pregnant or who are trying to become pregnant and those who are breastfeeding should talk with their doctors about limiting caffeine use.
Read on to see if you may need to curb your caffeine routine.
You drink more than 4 cups of coffee a day
You may want to cut back if you're drinking more than 4 cups of caffeinated coffee a day (or the equivalent) and you're experiencing side effects such as:
- Migraine headache
- Frequent urination or inability to control urination
- Stomach upset
- Fast heartbeat
- Muscle tremors
Even a little makes you jittery
Some people are more sensitive to caffeine than are others. If you're susceptible to the effects of caffeine, just small amounts — even one cup of coffee or tea — may prompt unwanted effects, such as restlessness and sleep problems.
How you react to caffeine may be determined in part by how much caffeine you're used to drinking. People who don't regularly drink caffeine tend to be more sensitive to its negative effects. Other factors may include genetics, body mass, age, medication use and health conditions, such as anxiety disorders.
You're not getting enough sleep
Most adults need seven to eight hours of sleep each night. But caffeine, even in the afternoon, can interfere with this much-needed sleep.
Chronically losing sleep — whether it's from work, travel, stress or too much caffeine — results in sleep deprivation. Sleep loss is cumulative, and even small nightly decreases can add up and disturb your daytime alertness and performance.
Using caffeine to mask sleep deprivation can create an unwelcome cycle. For example, you may drink caffeinated beverages because you have trouble staying awake during the day. But the caffeine keeps you from falling asleep at night, shortening the length of time you sleep.
You're taking medications or supplements
Certain medications and herbal supplements may interact with caffeine. Examples include:
- Ephedrine. Mixing caffeine with this medication — which is used in decongestants — might increase your risk of high blood pressure, heart attack, stroke or seizure.
- Theophylline (Theo-24, Elixophyllin, others). This medication, used to open up bronchial airways, tends to have some caffeine-like effects. So taking it with caffeine might increase the adverse effects of caffeine, such as nausea and heart palpitations.
- Echinacea. This herbal supplement, which is sometimes used to prevent colds or other infections, may increase the concentration of caffeine in your blood and may increase caffeine's unpleasant effects.
Talk to your doctor or pharmacist about whether caffeine might affect your medications.
Curbing your caffeine habit
Whether it's for one of the reasons above — or because you want to trim your spending on coffee drinks — cutting back on caffeine can be challenging. An abrupt decrease in caffeine may cause withdrawal symptoms, such as headaches, fatigue, irritability and difficulty focusing on tasks. Fortunately, these symptoms are usually mild and resolve after a few days.
To change your caffeine habit, try these tips:
- Keep tabs. Start paying attention to how much caffeine you're getting from foods and beverages, including energy drinks. Read labels carefully. But remember that your estimate may be a little low because some foods or drinks that contain caffeine don't list it.
- Cut back gradually. For example, drink one fewer can of soda or drink a smaller cup of coffee each day. Or avoid drinking caffeinated beverages late in the day. This will help your body get used to the lower levels of caffeine and lessen potential withdrawal effects.
- Go decaf. Most decaffeinated beverages look and taste the same as their caffeinated counterparts.
- Shorten the brew time or go herbal. When making tea, brew it for less time. This cuts down on its caffeine content. Or choose herbal teas that don't have caffeine.
- Check the bottle. Some over-the-counter pain relievers contain caffeine — as much as 130 mg of caffeine in one dose. Look for caffeine-free pain relievers instead.
The bottom line
If you're like most adults, caffeine is a part of your daily routine. And most often it doesn't pose a health problem. But be mindful of those situations in which you need to curtail your caffeine habit.