How much caffeine is too much?

So many people have caffeine on a daily basis, whether it's sipping a cup of coffee first thing, drinking an iced tea at lunch, or noshing on some dark chocolate after dinner. But if you've ever had too much caffeine, you know it — the jittery feeling, rapid heart rate and insomnia can be a lot to deal with.

That naturally leads us to ask: How much caffeine is too much? Like so many things in life, there’s no one-size-fits-all answer. Still, there are some general guidelines to follow.

Here's what you need to know about caffeine and how to make sure you don't overdo it.

What is caffeine, exactly?

You probably have some idea of what caffeine is, but it never hurts to review. Caffeine is a bitter substance found in more than 60 plants, including coffee beans, tea leaves, kola nuts (which are used to flavor colas) and cacao pods (which are used to make chocolate), according to the National Library of Medicine.

Caffeine can also be synthetic and added to some medicines, foods and drinks, like certain pain relievers, cold medicines and energy drinks. But most people have caffeine in the form of drinks like coffee, soda and tea, and the amount in each can vary. Here’s a breakdown, per the National Library of Medicine:

• An 8-ounce cup of coffee: 95 to 200 mg

• A 12-ounce can of cola: 35 to 45 mg

• An 8-ounce energy drink: 70 to 100 mg

• An 8-ounce cup of tea: 14 to 60 mg

How does caffeine impact the body?

Caffeine is a stimulant, which means that it speeds up the messaging between the brain and the body, Dr. Jamie Alan, associate professor of pharmacology and toxicology at Michigan State University, tells Yahoo Life. “It will increase heart rate, open up the lungs and increase wakefulness,” Alan says.

Caffeine can affect your nervous system, cardiovascular system, endocrine system and gastrointestinal system, Dana Hunnes, senior dietitian at the Ronald Reagan-UCLA Medical Center, tells Yahoo Life. “Caffeine is absorbed in the GI tract and is metabolized by the liver,” says Hunnes. The drug affects different people differently, depending on how quickly they metabolize it, she explains. “As for the nervous system, caffeine stimulates excitatory neurotransmitters, which increases alertness,” Hunnes adds.

Video: 5 ways to curb your caffeine addiction

The pros and cons of caffeine

There are pros and cons to using caffeine. “Some people find it makes them feel more alert and studies have even shown that it can boost athletic performance,” New York-based dietitian Jessica Cording, author of The Little Book of Game Changers, tells Yahoo Life. "Caffeine has also been shown to have positive effects on mood, energy and response times," Alan says.

Caffeine even has medical uses: It can help with pain, including headaches, and also stimulates smooth muscles in your body and can help with constipation, Hunnes says.

But there can be a definite downside to using caffeine. Too much of it can cause the following side effects, according to the Food and Drug Administration (FDA):

• insomnia

• jitters

• anxiety

• increased heart rate

• upset stomach

• nausea

• headache

• a feeling of unhappiness

How much caffeine is too much?

In general, the FDA recommends that you have no more than 400 milligrams of caffeine a day, the equivalent of four or five cups of coffee. But, the FDA says, there is a wide variation in how sensitive people are to the effects of caffeine and how fast they metabolize it.

Recommendations are slightly different depending on any underlying health conditions you may have. For example, the American College of Obstetricians and Gynecologists (ACOG) recommends that pregnant women have no more than 200 milligrams of caffeine a day.

“Everyone has a unique metabolism and even certain medications can influence how your body processes caffeine,” Cording says. “Starting with less is definitely better. It’s a hard cycle to break if you get into too much.”

But in general, the majority of healthy adults can drink 400 milligrams worth of caffeine a day and be fine, Hunnes says. “More than that should probably not be consumed,” she adds.

Why is too much caffeine bad for your health?

If you have too much caffeine in too short a time (such as consuming 1,200 milligrams), you can have seizures and even die, according to the FDA. “There are reports of caffeine toxicity from abusing energy drinks, especially in the male adolescent population, and this increased between 2004 and 2010,” Hunnes says. “Many different brands of caffeinated energy drinks exist and can contain as much as 500 milligrams of caffeine per can or bottle.”

Alan says that “some of the most serious effects would be cardiac effects,” adding: “Caffeine can certainly also mask sleep deprivation.” Meaning, you could not be getting enough sleep every night but may not realize you’re struggling because you’re relying on caffeine to stay alert. In addition, caffeine can affect your ability to fall sleep. “Caffeine can also be irritating to your stomach and your stomach lining,” Alan says.

People can even develop a dependency on caffeine where, if they don't have enough, they “find it hard to function and may develop flu-like symptoms,” Cording says.

If you’re unsure about your caffeine intake and think it might be too high, Cording recommends talking to your health care provider about ways to slowly cut back. Even regular coffee drinkers can experience withdrawal headaches when they suddenly, rather than gradually, stop drinking caffeinated beverages. “Sometimes it’s not realistic to go completely cold turkey,” Cording says. “But there are lots of approaches that can help, and help you actually stick to it.”

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