She's really little for being 6# at birth and definitely a slow grower. I'm surprised the DR has waited till now to start pushing formula. What does mom think? I'm assuming she's coming to you for help. I think the first basic thing anyone is usually told, at least what I was told was bf baby, pump, and then offer whatever mom got w/ the pump (a GOOD pump). Or sometimes the baby can't wait once they learn to recognize hunger cues and I gave whatever I had in the fridge or formula and then pumped. There are also many herbs out there to help w/ milk supply also, MOBI has a great list. W/ Ilana she was a happy to starve baby w/ a weak suck so everything was going against her. We started supplementing at 4 mos old while working on milk supply and she gained a # in the first week. She still was never big (until right before she turned 1 and then she hit 50%), but it was obvious she needed more food, she had just never learned to cry about it or something, who knows. She lets me know now, lol. We did have to keep supplementing till she weaned, but I've had to do that w/ all of them. I'm hoping for better this time.