5 week old won’t finish bottle

Lesley

My little one usually drinks between 2-3oz every 2 hours. Which I feel isn’t enough for his age and would love to increase. He’s currently on a preemie flow nipple in avent bottles. I’m wondering if I should up the nipple size or if this is just a phase.

He’s currently drinking 1 oz-2oz every 45 mins to an hour right now.