Our 6 week old is bottle fed (breastfeeding is not an option on this case for medical reasons). She’s now regularly downing the ~4.4oz bottles (4 oz water plus powder). Not every feeding but most times. She would keep going but the bottle is taken away.

However she only very rarely (maybe twice so far in a week and a half) seems still hungry after finishing it. And the 9 oz bottles seem so big for such a little thing.

Does finishing the bottle mean we should try offering more in a bigger bottle? Or wait for her to demand more? How do you know when to move up?