Up to 400 milligrams (mg) of caffeine a day appears to be safe for most healthy adults. That's roughly the amount of caffeine in four cups of brewed coffee, 10 cans of cola or two "energy shot" drinks. Keep in mind that the actual caffeine content in beverages varies widely, especially among energy drinks.
You drink more than 4 cups of coffee a day
You may want to cut back if you're drinking more than 4 cups of caffeinated coffee a day (or the equivalent) and you have side effects such as:
- Headache
- Insomnia
- Nervousness
- Irritability
- Frequent urination or inability to control urination
- Fast heartbeat
- Muscle tremors
