If your newborn is not gaining weight well (usually about an ounce a day in the early months), your doctor may suggest supplementing with formula. However, even if supplements are necessary short-term, it is important to find out why a baby is not gaining properly. There are often easy adjustments that you can make to improve baby's weight gain and restore exclusive breastfeeding. For example, a baby may need to breastfeed more times per day. If you're working, you may need to pump more often. If baby is nursing ineffectively, there may be an anatomical issue, such as tongue tie, which can be fixed to improve her breastfeeding. Find the cause of the slow weight gain to find the right solution.