Hi kat421,Thanks for your question. Some physicians charge by the area and some by the unit. At our clinic, we charge by the unit for most area as it seems fairer to charge for the amount of botox actually required to achieve the desired result. Patient A may need 20 units to relax the muscles around the outer eye area (crow's feet), whereas Patient B may require 30 units. As the medicament has a cost per unit, it makes more sense to charge patient A less than Patient B. However, for certain areas that require very few units, we charge by the area as there is a minimum charge for the act of injecting. In this case, the patient would only be treating that 1 small area requiring very few units (i.e., chin, gummy smile, nose, horizontal forehead lines). However if the small area requiring very few units was part of a more comprehensive BOTOX treatment, we would charge by the unit. Hope this helps. Best, Manish Khanna, MD FRCPC