I started using HiPP for my son when he was 4 months old, I stopped producing breastmilk due to extreme stress. My son had a very easy time switching to this formula, as it was gentle on his tummy. He seemed to enjoy it immediately to. He has just turned 1 and no longer needs formula, so he had his very last bottle tonight, full belly, empty container. He has never been underweight, and this formula helped him gain weight at a very healthy pace.we used formulas 1-3. I highly recommend this formula to all my mommy friends, especially since we have had the formula shortage, ive never had to worry about HiPP being in stock. If my husband and i decide to have another baby and i have trouble producing breastmilk again i wil 100% use HiPP again! Thank you for feeding my baby!