Did you now that approximately 75 to 80 percent of the total world population drinks caffeine regularly?  And that in the United States, about 90 percent consume caffeine in one form or another?
It may not be totally surprising given the benefits it brings, not to mention the amazing taste and aroma you may be looking for every morning. And it’s not totally a newsflash that a lot of people have formed a habit around coffee. In fact, studies say that over a quarter of those consuming caffeine fall under the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) Substance Dependence list. 
If you’re one of the coffee lovers wondering whether they may be having too much coffee, here are 5 signs that tell you it may be time to take it easy:
#1 You feel moody and grumpy before your first cup of joe.
Based on a review conducted by A. Nehlig, having 75 mg of caffeine (a cup of joe) every 4 hours can lead to a “pattern of sustained improvement of mood over the day.” It can increase alertness and well-being, help concentration, improve mood and limit depression. 
But too much of this good thing can get you hooked!
According to Dana Hunnes, Ph.D., M.P.H., R.D., senior dietician at UCLA Medical Center and adjunct assistant professor at the Fielding School of Public Health, caffeine “stimulates the dopamine receptors in our brain, kind of like cocaine and other certain drugs, just not nearly to the same extent." 
Because it affects your mind this way, too much coffee may lead to dependence. Because the coffee euphoria feels good, you may find yourself reaching out for another cup.
And if the next time you’re feeling moody and grumpy, check yourself. Do you feel the need to get another caffeine fix? Do you feel like a cup can get you more emotionally stable and back in a great mood again? If you said yes and yes, then it’s your body telling you to chill and take it easy on your coffee.
Plus, if you often find yourself grumpy and just a plain zombie right after getting out of bed, then it may be another sign that you may have developed a tolerance for the positive mood-altering effects of coffee.
#2 You feel immune to the benefits of coffee.
In the coffee junkie’s world, this is called caffeine tolerance.
Drinking too much coffee every day may lead to tolerance, prompting your system to get more than your usual fix to get the same benefits.
An article on Caffeine Informer talks about caffeine tolerance.  It says that a first-time coffee drinker (or someone who has been off caffeine for a long time) has zero-tolerance. And these people get the most bang for the cup – euphoria, alertness, good mood, and increased energy and motivation.
But having too much may increase the tolerance, and hence wean off caffeine’s benefits. If you notice that your usual cup or two don’t perk you up anymore, it may be a sign that you’ve developed a tolerance for caffeine.
If after a cup or two you feel jittery and anxious – instead of being perky and alert – then you may have gone overboard with coffee.
Loading up on caffeine may lead to high anxiety and even panic attacks, especially for those who have mental health disorders. If you’re starting to notice yourself being high-strung and on the edge often, then it may be time to wean off your caffeine intake.
#4 You suffer from headache when you don’t get your caffeine fix.
Did you know that caffeine helps ease migraine headaches? In fact, it helps pain relievers and headache meds work more effectively.
Moments before migraine strikes, blood vessels start to enlarge. What makes caffeine an effective pain reliever is its vasoconstrictive properties that restrict blood flow, narrowing the blood vessels and eventually helping ease the pain.
But having too much caffeine can create the opposite result – it could lead to headaches. There are two reasons why:
Withdrawals. Loading up on caffeine a little too much can result in tremors, nervousness, and sleep interruptions. When you develop caffeine dependence, trying to get rid of it, even having less than your usual fix, can cause a headache. This is a clear symptom of withdrawals.
Based on research done at the John Hopkins Medicine Behavioral Pharmacology Research Unit, approximately 50 percent of coffee drinkers suffer from withdrawal headaches after skipping their caffeine fix for a day. 
Medication rebound can also take place, triggered by heavy dependence on pain relievers. With medication rebound, a headache with even more intense pain may start to form when the effects of pain medicine wear off.
#5 It’s hard to concentrate
Aside from perking you up, caffeine can also help you concentrate and become more productive?
If, during mind-numbing, brain-wracking moments, you want to feel like Popeye going for a whole can of spinach, just reach out for the coffee-maker and you’re likely to feel the same.
But too much caffeine may negate this. If you’re wondering how much is too much, the magic number is 400 mg. If you want to know more how many cups of coffee or cans of cola 400 mg represents, then check out this article: How much caffeine should you have in a day?
There are supplements that can give you that caffeine fix while ensuring that you benefit from well-oiled cognitive functions.
Erectile dysfunction. In combination, those are two of the ugliest words known to man. But can caffeine help you get it up?
Science hasn't found the definitive answer to this question, but one study concluded that fewer men who consume caffeine have problems performing. The study said:
Caffeine intake reduced the odds of prevalent ED, especially an intake equivalent to approximately 2-3 daily cups of coffee (170-375 mg/day). This reduction was also observed among overweight/obese and hypertensive, but not among diabetic men. Yet, these associations are warranted to be investigated in prospective studies