Too much caffeine causes unwanted negative side effects that outweigh the otherwise positive benefits of caffeine. Like other stimulant drugs, caffeine can lead to difficulty sleeping, restlessness, and anxiety. As with all drugs, people's sensitivity to caffeine will vary. For sensitive individuals, any caffeine may be too much, while others may tolerate or even enjoy a good deal of caffeine. Ultimately, it is up to each individual to determine how much caffeine causes enough negative side effects to make it unpleasant or no longer enjoyable.
The best way for an individual to determine how much caffeine is too much is to know how much caffeine is in various beverages and which side effects a person is most likely to experience. Caffeine content is usually measured in milligrams (mg). Caffeinated sodas usually contain about 50 mg of caffeine. A cup of coffee usually contains about 200 mg, a shot of espresso about 200 mg, and tea 50 to 100 mg. Keeping track of caffeine intake will help determine when a person has had too much.
One of the best known caffeine side effects is insomnia, which often occurs when a person drinks caffeine too close to a scheduled bedtime. People can determine when they've had too much caffeine by whether or not it keeps them up at night. For some, this is any caffeine in the evening, while others may tolerate caffeine until bedtime.
Another common side effect of consuming too much caffeine is known as the caffeine jitters. Symptoms include trembling and nervousness, as well as difficulty concentrating or keeping still. The amount of caffeine it takes to produce this condition needs to be determined by observing one's own caffeine intake, including all sources. People who are naturally anxious may find that even small amounts of caffeine are enough to make them feel jittery. In such individuals, too much caffeine can cause anxiety or even panic attacks.
Large amounts of caffeine can cause a number of other undesirable effects associated with stimulants. Some of these effects include a pounding or rapid heartbeat, diarrhea, and dizziness. Too much caffeine can be lethal when taken in a pill form like diet pills, but this takes thousands of milligrams of caffeine.
Consuming too much caffeine can lead to a state of dependence, which is sometimes informally referred to as caffeine addiction. Signs of dependence include being irritable, depressed, or unable to concentrate without caffeine. Physical symptoms such as headaches and excessive fatigue are also indications of dependence. Symptoms of dependence usually clear up after an individual cuts down or stops using as much caffeine. All sources of caffeine, including soda, can produce dependence.