Breastfeeding is not recommended for patients with hyperthyroidism who are taking antithyroid medications. Patients with hyperthyroidism who have stable thyroid hormone control and do not need to be treated with medications are usually allowed to breastfeed, and it is recommended that you consult your doctor. Patients with hyperthyroidism need to be treated with medications such as methimazole and propylthiouracil, which may cross the placental barrier and be secreted through breast milk, so breastfeeding is not recommended for patients with hyperthyroidism who are taking these medications. However, patients with hyperthyroidism whose thyroid hormones are within reasonable limits and who are not currently treated with antithyroid medications are generally able to breastfeed. It is recommended that patients with hyperthyroidism who are breastfeeding go to the hospital and consult with a medical professional to determine if they are able to breastfeed.