If you are consistently producing more milk than baby needs, try nursing on only one breast per feeding. If baby is already taking only one breast per feeding, try using only one breast per four-hour period. (For example: left breast from 8 to 12 a.m., right breast from 12 to 4 p.m., and so on.) This “block feeding” can signal your body to slow down milk production a tad. If one of your breasts becomes uncomfortably full during this experiment, express just enough milk to relieve the pressure. You should notice a reduction in milk supply within a few days to a week. As soon as you notice your milk supply getting under control, resume breastfeeding as usual. (Remember to let baby nurse on the first breast as long as he wants before switching. You may not need to feed from both breasts at every feeding.)
Peppermint is also said to ease your milk supply. So sipping mint tea or popping Altoids might help. Sage capsules (available at health food stores) have been helpful in reducing milk supply for weaning. But talk to a doctor or lactation consultant before taking any herbal supplements to reduce your supply.