How Much Solution Should Be Added Per Botox Vial?

This is a matter of personal preference. The package insert for Botox cosmetic recommends 2.5 cc but physicians inject anywhere from 1 to 10cc according to their own treatment protocols.

There are only 100 units per vial, the recommended dilution is 2.5 cc of sterile saline.  Atlanta Plastic  Surgeon, Dr. Z