Too much supplementation means baby is getting less of the parent’s own milk, and eventually less milk production for the parent. Too little supplementation means baby is not fed enough. So how to find that juuuuust right amount? Or even to determine whether supplementation is really necessary? And, when necessary, how to supplement in a way that preserves long-term breast/chestfeeding outcomes? This presentation can serve a guide for if, when, how and how much to supplement direct breast/chestfeeding with additional human milk or infant formula.