Siobhan, for the most part the meds you take replace what your body isn’t producing, so there really shouldn’t be any excess of the hormones in the milk your baby would drink. But, the milk production does drain energy, so you’ll want to pay closer attention to how you feel, and make sure you’re getting enough of the medicine, as well as a generally healthy diet, making sure to replace the calcium lost in the milk. I don’t know if they have it where you’re from but mustard greens are supposed to be extremely high in calcium.