You do not need to switch to Stage 2 formula the exact day your baby turns 6 months; you can finish your current tin of Stage 1 first. When you are ready, it is best to introduce the new stage gradually by replacing one feed at a time over a few days to monitor for any digestive discomfort, though many babies transition without issues. Always follow the specific mixing ratios provided on your formula’s packaging rather than standardizing based on internet advice, as density and scoop sizes vary significantly by brand.