Weaning from breast to cup depends on your baby's need to suck and his ability to drink from a cup. A baby is usually willing to wean between 9 and 18 months. If your baby is less than 9 months old, you should wean him to a bottle first. When your baby is 6 months old, you can start giving a cup, but wait to completely wean your baby until he is about 9 months old.
You can put breast milk that you have pumped and stored in the cup. You can also use formula in the cup. If your baby is over 12 months you can use regular whole milk.
If you use formula:
If your baby is taking a daily total of 16 to 20 oz. of milk by cup, in addition to 3 meals of solid food, he can be considered successfully weaned.
If your breasts become engorged because you are not nursing as much, allow your baby to suck 15 to 30 seconds from each breast to relieve your discomfort. Make sure that you don't nurse any longer, however, or you will trigger your breasts to produce more milk—and the engorgement will get worse.
Setbacks in weaning can be caused by many things, including stress, major changes in meal or bed times, or illness. If such setbacks occur, wait until the situation improves or the illness is over, and then continue the weaning process. Call your baby's healthcare provider if you have any questions or concerns.
If your child does have a sippy cup, use it only at the table or while your child is in the high chair. Children should not be allowed to walk around with a sippy cup. Carrying a sippy cup allows a child to get attached to it for comfort. Because calorie-rich drinks are usually in the sippy cup, the child learns that food means comfort. This is not a good idea. The sippy cup may be bad for teeth, both causing tooth decay and overbite of the upper teeth. Wean your child to an open-rimmed cup as soon as feasible.