How much caffeine is too much caffeine?

Depends: At your age without any cardiac problems or pregnancy or thyroid problem, about 3 -4 cups a day would be safe. If you really like to drink more, then drink decaf.

Each person's unique: However, it would be a bad idea to go over 800mg/day for anyone more than very rarely. People who find no unpleasant effects might be okay with 500-600mgs but most would be happier at 300mg/day. A normal cup (not mug) is approx 100mg. Don't forget other sources in your diet count too! A big part is how you feel.

More than 2 cups/day: In smaller amounts, caffeine has actually been considered to have some health benefits. Up to two cups of coffee daily, for example, would be a safe and potentially beneficial amount to drink. Any more than that may cause you some trouble - stomach upset, bone loss, etcetera.

How much caffeine is too much varies from one person to another just like alcohol. There are people that cannot tolerate any caffeine ; and like alcohol eating and other things may affect how much caffeine an individual may be able to tolerate from time to time.