Caffeine comparison

Type of coffee, 6–ounce cup	Milligrams of caffeine per serving*
Brewed, drip method	115
Brewed, percolator method	80
Instant, 1 rounded teaspoon	65
Decaffeinated	2
Flavored, regular and sugar–free	25–75
Espresso (1.5 to 2 oz.)	100

*Amounts can vary
Not a benign brew
Coffee isn’t harmless, though, depending on how sensitive you are to caffeine, even a couple of cups of coffee can affect your.
Nervous system
Too much caffeine can make you nervous, restless, anxious and irritable. It can also increase your heart rate, make panic attacks worse and cause insomnia.
Digestive system
Caffeine causes the band of muscle separating your esophagus and stomach to relax. This allows stomach acids to back up into your esophagus, producing heartburn. Caffeine may also irritate existing stomach ulcers by increasing stomach acid secretion, and cause constipation, diarrhea and gastrointestinal upset.
Bladder
Caffeine’s been known to cause bladder irritation in some people. It’s also a mild diuretic, causing you to urinate more.