define pg/ml
It means picograms per milliliter (pg/ml). The picograms would refer to some type of substance dissolved in a solution which is represented by the milliliters. This is referred to as a concentration. For example, it could be the measure of the amount of a drug in the blood stream. Picograms are 1 gram x 10 raised to the -12........a very very small number. Milliliters is 1/1000 of a liter. Whatever it is referring to, it is in a very low concentration. I would go to another vet for a second opinion if I were you.