Sage
This is best used only if you are in the process of weaning, though it may also be used in extreme cases of oversupply when the usual measures are not effective. Be careful with this if you are not in the weaning process! Don’t overdo it once you’re seeing some results.
To use dried sage (Salvia officinalis) for reducing milk supply, take 1/4 teaspoon of sage 3x per day for 1-3 days. You can mix the sage in vegetable juice (for example, V-8), but it won’t mix well into other juices. You can also mix it into other foods or a broth. If you don’t like the taste of sage, try putting it into a tiny piece of sandwich and swallowing it whole – peanut butter or something else a bit sticky seems to work best for holding the sage in place. Tear off the corner of the sandwich containing the sage (it should be a very small section) and swallow it without chewing (that’s why you need a very small section).
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To use sage tea for decreasing milk supply, infuse 1 tablespoon of dried sage in 1 cup of boiling water. Steep for 5-15 minutes. Drink 1 cup, 2 – 6 times per day.
You can use a tincture of sage instead: 30-60 drops of tincture, 3-6 times a day. Do not use sage essential oil – it should not be taken internally.
Cabbage
Green cabbage leaves can also be used topically on the breast to reduce milk supply. Again, be careful with this if you are not in the weaning process.
Jasmine
Another effective treatment is to apply fresh, crushed jasmine flowers (Jasminum sambac) to the breasts to decrease milk flow. A study has shown this to be effective: Shrivastav P, George K, Balasubramaniam N, Jasper MP, Thomas M, Kanagasabhapathy AS. Suppression of puerperal lactation using jasmine flowers (Jasminum sambac). Aust N Z J Obstet Gynaecol. 1988 Feb;28(1):68-71.
Other herbs
Other herbs that can decrease milk supply: Peppermint (Mentha piperita), Spearmint, Parsley (Petroselinum crispum), Chickweed, Black Walnut, stinging nettles (not nettle – that increases milk supply), Yarrow, Herb Robert (Geranium robertianum), Lemon Balm, Oregano, Periwinkle Herb (Vinca minor), Sorrel (Rumex acetosa).
Sage, peppermint, spearmint, lemon balm, oregano, and cabbage leaves can all be incorporated into a pressed oil (cold pressed or hot) to make massage oils for milk suppression.
Peppermint essential oil has been used traditionally for decreasing milk supply. Peppermint tea is a very weak form of peppermint and only large amounts (quarts) would be expected to decrease milk supply. Some women have successfully used the strong peppermint candies (for example, Altoids® Curiously Strong Peppermints) for decreasing milk supply (a few per day aren’t likely to affect supply, though).
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Comfort measures for mom during weaning
Birth control pills are well known for decreasing milk supply, particularly the ones that contain estrogen.
Sudafed (a decongestant) can also decrease milk supply, particularly with regular use.