Noni- The box says 4months but the boys were 3 months and My cousins sons were 6wks and 8wks. I did it with Olivia cause I didnt want to increase her bottles but she seemed to me like she wanted more only on occasion. I am also starting her on water at the end of this week. For myself as a rule I always try new stuff like feeding foods and medicine at the begining of the day cause that way if they have a reaction to it, it is a lot easier to deal with it (like going to the doctors or hospital) during the day then late at night also during the day I can watch them more closely.