Healthy adults can safely have a moderate amount of caffeine daily or about 200 to 300 milligrams (mg), which amounts to 2 to 4 cups of brewed coffee a day.
Pregnant women and lactating mothers may want to skip caffeine altogether.
The Mayo Clinic says that consuming heavy amounts of caffeine each day (more than four cups a day) may lead to muscle tremors, insomnia, irritability, fast heartbeat or frequent urination.