What is the highest amount of vitamin c someone can take in one day without hurting their health?

Depends . . .: Everything depends, right? Well, 1st, it depends upon who you ask. 2nd., it depends upon age. 3rd, depends upon goal (are you trying to cure scurvy or prevent something?). Fda set a tolerable upper intake level of 2, 000mg/d back in 2000 (http://lpi.Oregonstate.Edu/infocenter/vitamins/vitaminc/index.Html#safety) for adult men & women. Also check out mayo clinic (http://goo.Gl/17fshu).