Boston had gastro at 2 weeks of age and I was told to give nothing but Gastrolites for 2 days. I wasn't happy with this so rang the pead who suggested a lactose free formula made at half strength for 24 hours then to continue with the lactose free formula for a few days until I was happy and then swap back to my normal formula. The lactose free definatly helped his tummy and he was great after that. Hope this helps.