TL;DR The ideal amount of caffeine intake in a day boils down to 400 mg, which is equivalent to many different things depending on the food or drink you're taking. When you consume more than this amount, some adverse effects may take place like headache, anxiety, and insomnia.
So, which of these have you popped or downed today?
These products all contain varying amounts of caffeine, alongside others you wouldn't have thought to contain it. Ice cream, frozen yogurt, breakfast cereals, pudding, pain medications … even cocoa butter lotion apparently all have it! 
Do you like most (or all) of these products? Then you must be wondering how much caffeine you take in daily.
We've got you covered.
Keep reading to find out the safe amount to consume and what might happen if you get too caffeine-happy.
What's the safe amount of caffeine to consume in a day?
Let's start with a very important question:
How much is too much?
Studies have shown that caffeine remains in the safe zone when consumed in low-to-moderate amounts . But what exactly does “low-to-moderate” mean?
The most important figure to remember on this topic is...
400 milligrams (mg).
That’s the amount of caffeine that’s considered safe to consume in a day… at least for adults. 
If you’re wondering what 400 mg means, you can refer to image below:
Note that caffeine content varies in different products so don’t forget to check the label!
And if you’re wondering how much the “killer” amount is (literally), then USA Today reports it would “likely take anywhere from 50-100 cups of coffee,” or a teaspoon of pure powdered caffeine ingested at once. 
Now you must really love your caffeine to death if you take in that much!
What happens if you consume more than that?
Crossing the line, aka going beyond 400 mg or 1/16th teaspoon of pure powdered caffeine, may lead to the following adverse effects: [5, 6]
Drinking too much coffee or tea can cause withdrawal symptoms, caffeine rebound and medication rebound, which can all lead to migraine or the worse version of your typical headache. How this happens is covered in our article “Does caffeine cure or cause migraines?”
From modest doses [7, 8] to incredibly high intake (1,000 mg or more) a day [9, 10] caffeine could cause nervousness, rapid breathing, stress and mood swings. And studies say these adverse effects can take place regardless of how many times you have your caffeine – whether you’re a coffee-lover or just an occasional drinker. 
Caffeine can cause sleeplessness, especially when consumed beyond 3 PM. Studies show that having more than you’re supposed to can eat up on your sleeping time, especially among seniors. [12, 13]
Excessive caffeine intake can also cause rhabdomyolysis, which is a “serious syndrome due to a direct or indirect muscle injury. It results from the death of muscle fibers and release of their contents into the bloodstream.” [14, 15, 16, 17, 18]
One study cited a woman who guzzled a liter of coffee with 565 mg worth of caffeine and eventually suffered from symptoms of rhabdomyolysis, i.e. nausea, vomiting and dark urine. Don’t worry, she recovered after getting medical attention. 
High blood pressure
Caffeine as a stimulant has been observed to temporarily increase blood pressure among non-habitual coffee drinkers. [20, 21, 22, 23]
The same happens during exercise among healthy people and those with “mildly elevated blood pressure” alike. [24, 25]
Rapid heart rate
Stimulant overload can also alter the rhythm of your heartbeat, which was reported among young people who had gone overboard with their energy drinks. 
More trips to the toilet
Most research reports higher likelihood of frequent urination or inability to control urination with excessively high caffeine intake, especially among older people or those suffering from incontinence.
In some cases, high consumption may even likely develop incontinence among those with a healthy bladder. 
Who should and shouldn’t be having caffeine
While caffeine may be safe for adults, its effects could vary based on people’s tolerance. Research shows that genes may have something to do with it. That’s why some can have more cups of coffee over others without having any drawbacks. [28, 29]
Some people though should carefully watch their intake, especially the following:
Children and adolescents should limit consumption as they may be “particularly vulnerable to the negative effects of caffeine” 
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