TL;DR While caffeine has various health benefits, having too much has its downsides too. This article lists down various signs and symptoms that you may be having one too many cups of joe.
Do you find yourself heading to the coffee-maker straight from bed? Then you’re one of 62% Americans who drink coffee every single day.  Call it a morning ritual or a habit that can’t be shaken, but it’s pure unadulterated java love.
Some, however, call it caffeine addiction.
Of the American adults who take caffeine daily, half or more of them are subject to caffeine withdrawal symptoms when they don’t get a fix (more on this later).
When you have your daily caffeine fix for a long period (we’re talking about years here), your brain chemistry and receptiveness to the stimulant changes.  What happens is that because caffeine mimics adenosine, your brain tries to keep up with the additional “adenosine” by creating more receptors. As a result, your brain tells your body to “want” more caffeine to fill up these vacant receptors - a.k.a. you wanting more caffeine.
And if you suddenly halt your caffeine intake, then you’re in for some adventure... an unpleasant one at that.
Quitting cold turkey is like signing up for seemingly eternal feelings of tiredness, and other symptoms of caffeine withdrawal. 
Related article: What are caffeine withdrawal symptoms and how to reduce them
Caffeine withdrawal symptoms may strike people who have doses as low as 100 milligrams a day. That’s equal to about 6 ounces of brewed coffee or two cans of soda. Experiments have shown that about half regular drinkers of coffee or consumers of caffeine in other products get withdrawal headaches when they abstain.
“When all withdrawal symptoms are considered, the incidence of caffeine withdrawal is higher,” the Johns Hopkins states. “In a population-based random digit dial telephone survey study, 40 to 70% of individuals who tried to quit caffeine use reported experiencing withdrawal symptoms.
While caffeine has various health benefits, having too much has its downsides too.
You know when you’ve gone overboard when: first, you’ve had more than the required daily intake. Here’s how much caffeine you should have in a day.
Second sign? When you start getting symptoms of caffeine addiction, like the following: 
Johns Hopkins Medicine’s Behavioral Pharmacology Research Unit calls caffeine the most common mood-altering substance used in the world: 
The mood-altering effects of caffeine depend on the amount of caffeine consumed and whether the individual is physically dependent on or tolerant to caffeine. In caffeine non-users or intermittent users, low dietary doses of caffeine (20-200 mg) generally produce positive mood effects such as increased well-being, happiness, energetic arousal, alertness, and sociability. Among daily caffeine consumers, much of the positive mood effect experienced with consumption of caffeine in the morning after overnight abstinence is due to suppression of low-grade withdrawal symptoms such as sleepiness and lethargy (see section on Caffeine Withdrawal). Large caffeine doses (200 mg or greater) may produce negative mood effects. Although generally mild and brief, these effects include increased anxiety, nervousness, jitteriness, and upset stomach. However, individual differences in sensitivity and tolerance affect the severity and likelihood of experiencing negative effects.
People who consume caffeine may be unaware of their physical dependence on the chemical because they get caffeine every day. Also, low doses, as little as 25 mg, can prevent withdrawal symptoms from occurring. So a caffeine “addict” may forego his usual three cups of coffee but get enough caffeine from a chocolate bar or energy bar to forestall the worst symptoms.
“Thus, some people may report never experiencing withdrawal because they unknowingly consumed small amounts of caffeine on days they thought they had been caffeine free. Finally, caffeine withdrawal symptoms (e.g., headache, nausea, muscle aches) may be misattributed to other causes or ailments (e.g., viral infection),” Johns Hopkins states.
Viter Energy doesn’t want to seem alarmist about caffeine. We love it.
Some believe it's more of dependence than an addiction, though.
According to WebMD, caffeine only causes a mild physical dependence.  To be termed as addictive, it must pose a threat to your physical, social, occupational, or economic health.
Caffeine is a stimulant to the central nervous system, and regular use of caffeine does cause mild physical dependence. But caffeine doesn’t threaten your physical, social, or economic health the way addictive drugs do. (Although after seeing your monthly spending at the coffee shop, you might disagree!)
If you stop taking caffeine abruptly, you may have symptoms for a day or more, especially if you consume two or more cups of coffee a day. …
No doubt, caffeine withdrawal can make for a few bad days. However, caffeine does not cause the severity of withdrawal or harmful drug-seeking behaviors as street drugs or alcohol. For this reason, most experts don’t consider caffeine dependence a serious addiction.
The good news is caffeine does not threaten consumers’ health as far as cancer, heart disease or reproductive problems, though some types of coffee have lipids that may raise cholesterol. Also there may be a link between taking large amounts of caffeine and delayed conception and lower weight of babies at birth.
People may want to try to quit caffeine for several reasons. Some don’t want to have to be tied to a routine where they must get their two or three cups of java, tea or soda at certain times of the day. Others may balk at being classified as an addict of any kind. Still, others may be pregnant and don’t want to risk their baby being underweight at birth.
If you want to cut the caffeine out of your diet, CaffeineInformer.com has some tips on getting off of it: 
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Is there a big difference between synthetic and natural caffeine? Which gives a stronger jolt? Does it even matter?
Natural caffeine in coffee, tea, and chocolate is much less common than the synthetic caffeine found in so many other products.
Caffeine is found in plant species such as the more popular ones like Coffea arabica and Coffea robusta, as well as tea leaves, kola nuts, cacao beans, Yerba mate and guarana berries.
Not only does naturally-occurring caffeine from said plants keep your cognitive functions at their peak, but it also contains antioxidants that help you fight illnesses like cancer and Alzheimer’s.
Caffeine is NOT addictive, but it sure is habit-forming. You don’t hear about coffee addicts robbing stores and hijacking motorists to get money for a fix. That’s because while caffeine does cause dependence, it isn’t in the same category as opiates or alcohol.