It depends on the child's age, weight, and other health factors. However, many experts recommend starting rice cereal in a bottle at around 6 months old. If your 1 month old infant is taking regular breast milk or formula, then you can begin slowly transitioning them to rice cereal by mixing a small amount of the cereal with their milk or formula each day. Alternatively, you can give them a full serving of rice cereal every day straight from the bottle. Just be sure to watch your baby closely for any negative side effects (such as constipation) that may occur as they transition from breast feeding or consuming formula exclusively to drinking large amounts of rice cereal every day.