Premature babies need to take preterm formula. Preterm babies on preterm formula usually need to wait until the preterm baby reaches the weight of a normal full-term newborn before the intake of preterm formula can be stopped. This process can be as short as a few days or as long as a few months. Preterm formula is categorized into inpatient preterm formula, and post-discharge preterm formula. The former is intended for the early, rapid catch-up growth of preterm babies during hospitalization, while the latter is mainly for post-discharge preterm babies. There are many differences between the two in terms of calories, nutrient ratios, and osmolality. But both formulas need to be eaten as required until the preterm baby reaches the same weight as a full-term newborn before it is recommended to stop. The time it takes for each baby to reach this standard when formula fed to a preterm baby varies greatly, so regular pediatric evaluation is required for as little as a few days or as long as a few months. It is important to intensify the pediatric check-ups of premature babies, in order to obtain timely and useful information on parenting, as well as to detect problems early and, if necessary, to start treatment as soon as possible.