If someone were to take 6 500mg of amoxicillin at once, what would happen?

Large dose: That's quite a large dose of amoxicillin - although not really harmful. You might have some GI symptoms - nausea or cramps. The good thing, however, is the medication is not very toxic AND it has a very short half-life which means it would wash out of your system quite quickly. It is important to know more about the CIRCUMSTANCES of this incident -so I hope you would talk to a doctor right away.