Your breast milk production can best be described as a supply and demand relationship. The more you nurse, the more milk your body will produce. It often feels like a teeter totter that can easily be thrown off balance if you're not conscious about maintaining (and not over-producing) your milk supply. Although a genuine low milk supply is rare, many moms try to increase their milk supply for a variety of reasons. But just how long does it take to increase your milk supply? The answer depends largely on how often you're nursing or pumping and your body's response to the milk making hormones.
According to Healthy Children, it can take a little while for your milk supply to fully establish itself after giving birth. So if you're concerned that you're not making enough milk right at the beginning, don't worry — things will balance out as your nursing schedule stabilizes. Later on though, if you're not diligent with nursing often, not supplementing with other liquids, and pumping if you need to or want to, your milk supply can suffer.
Your body is more intuitive than you may realize. According to La Leche League International (LLLI), a mother's body will know how much milk to produce after six weeks if she's nursing consistently. As your body adjusts, your breasts won't feel constantly full, like they once did, but this doesn't mean you have a low supply, it simply, as the LLLI article states, means you and your baby have developed a healthy routine.
If you truly are wanting to increase your supply though, increasing the length of your nursing sessions, adding a pumping session or two, and eating foods thought to boost your milk supply can help. For some women it may take only a few days, and for others it might be a few weeks to get things back in balance, but luckily, the supply and demand of nursing means that your supply can be adjusted if need be.