My left breast is not producing milk.
Most women have one breast that produces more milk compared to the other. In some cases, particularly if a woman has had surgery on her breasts (breast implants, large biopsies, or breast reductions), one breast produces close to nothing. In most women, however, the body makes more or less milk based on demand. In the early phases of breastfeeding, some babies prefer one breast over the other and, based on that, some mothers feed more on one side. Therefore, the breast that is not "used" as much does not produce as much milk. If you are just starting to breastfeed your newborn, I recommend feeding on both sides evenly and then trying to pump in-between feedings, particularly on the side that is making less. More stimulation will increase demand and hopefully increase milk production. It may also be helpful for you to see a lactation consultant. They can be extremely helpful in helping with many breastfeeding issues.