If One Unit of Botox is Derived from a Lethal Mouse Dose How Many Units Would Kill a Human?

The mice used to test Botox weigh around 25g or 1/20th of a pound, sometimes less.  The LD50 or dose required to cause death in half of mice injected with Botox is where the unit of Botox is derived.  1 unit kills half of mice injected after 3-4 days.  Transferring this to humans, you'd need around 3000 units to kill an average sized person, or 30 100unit vials.  Since the average cosmetic Botox injection is only around 30-50 units, you have virtually no chance of an adverse event such as death. You are much more likely to have an allergic reaction or not respond at all, both of which are also uncommon.

It would be next to impossible to run into problems with using quality cosmetic-grade Botox (e.g. made by Allergan). You would require at minimum 25 full vials of Botox injected in to you to have any problems, and this would never happen unless you had a death-wish.