Most newborns (2-3-week-old baby) that are formula-fed or breast-fed should be fed every 2 to 3 hours. As they grow older and their tummies can comparatively hold more milk, they usually demand consumption of it every 3 to 4 hours. And if the baby is very young, or is facing problems gaining weight, you should never go too long without feeding, even if it requires waking your baby. In such a condition, seek your doctor's help, talk to him about how often your baby should be fed. Feed them right so that they can grow both physically and mentally in their upcoming life.