Karen, I don't have an answer to the amount of milk that must be ingested in order to obtain an accurate PKU but here in Maryland it seems to be moot point. The same test covers many other inborn errors of metabolism that are not affected by milk intake and must be done prior to infant discharge. The pediatricians do a repeat PKU (maybe repeat of the other tests too, I don't know) in the office, usually at the first visit. Carla