Breastfeeding and Hyperthyroidism

Hispanic mother breastfeeding newborn baby in a hospital
MNPhotoStudios / Getty Images

When it comes to nourishing a newborn, no one would argue that for most moms and their babies, breastfeeding is best. A mother's milk is naturally flowing with all of the nutrients an infant needs to grow and flourish, and nursing can help a woman's recently-pregnant body return to "normal" more quickly and easily.

In some cases, however, breastfeeding can cause a new mom's thyroid gland to produce too much thyroid hormone, condition hyperthyroidism. Symptoms of an overactive thyroid include weight loss (more than is healthy for adequate milk production); anxiety; increased heart rate or palpitations; insomnia; feeling over warm; and sweating.

Hyperthyroidism While Breastfeeding

If you were being treated for Graves disease or a hyperthyroid condition before you became pregnant, you should continue to see your doctor for monitoring throughout your pregnancy and while you're breastfeeding. Your thyroid levels may change as your body changes, so your doctor may need to adjust your medication during and after your pregnancy.

If you have not had any thyroid issues in the past, thyroid symptoms can begin after you give birth. Some women develop mild hyperthyroidism followed by hypothyroidism in the months after the birth of their baby. This is called postpartum thyroiditis. The overactive phase of postpartum thyroiditis usually resolves itself within a few weeks and doesn't necessarily require treatment. However, if the symptoms of hyperthyroidism are severe or last longer than a few months, your doctor may put you on a low dose of medication and carefully monitor both you and your baby.

Breastfeeding with hyperthyroidism can be challenging. In addition to typical symptoms, an overactive thyroid may cause a slow or difficult let-down reflex and an overabundant supply of breast milk.


There are several ways to diagnose an overactive thyroid, including blood tests, ultrasound, and/or needle biopsy of the thyroid. All are safe for you and your baby while you're breastfeeding.

Another diagnostic technique, a thyroid scan, involves using radioactive iodine and is not a safe way to check thyroid function for a nursing mom. If for some reason your doctor wants to do a thyroid scan anyway, do not breastfeed your baby for 48 hours after you drink the radioactive iodine. During that time pump and dump your breast milk so your breasts don't become engorged and your milk production doesn't slow down.

Sometimes radioactive iodine is used to treat hyperthyroidism. If this turns out to be the only option for you, you'll need to wean your baby before you begin. You can pump and dump your milk during this time if you'd like to start breastfeeding again after you're no longer taking the iodine. Just keep in mind that it will take weeks or even months, depending on your dose, before all traces of the medication are out of your body.

Tips for Breastfeeding With Hyperthyroidism

There's rarely any reason to completely abandon breastfeeding when you've been diagnosed with an overactive thyroid. As long as you see your doctor for regular monitoring and follow the advice that follows, you and your baby should be able to enjoy the benefits of breastfeeding.

  • Your doctor may you on an antithyroid medication such as PTU (propylthiouracil) or Tapazole (methimazole), both of which work by helping your body make less thyroid hormone. These drugs are safe to take while nursing because very little of the active ingredients in them pass into breast milk. Even so, time your doses for after you feed your baby.
  • Smoking isn't safe or healthy in any situation, but for someone with hyperthyroidism lighting up can make symptoms worse. The only real option here if you're nursing is to kick the habit.
  • Stress also can increase symptoms of an overactive thyroid. To counter stress, be sure to eat well, get plenty of rest, and try relaxing activities like meditation, yoga, or a hobby.
  • Until your hyperthyroidism is under control, your body may produce more milk than your baby needs, leading your breasts to become engorged. Wear a supportive nursing bra, pump and save any milk your baby doesn't empty from your breasts after each feeding, and use cold compresses on your breasts if they becoming swollen or painful. Your doctor also may give you the go-ahead to treat discomfort with Tylenol (acetaminophen) or Motrin (ibuprofen).
  • If your doctor feels it's necessary to remove some or all of your thyroid, a procedure called a thyroidectomy, you will need to be away from your child during the surgery, of course, but once it's over and you feel up to it, you can begin breastfeeding again.
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  • American Academy of Pediatrics. "The Transfer of Drugs and Therapeutics Into Human Breast Milk: An Update on Selected Topics." Pediatrics. 2013. 132(3): e796-e809.

  • Glatstein M. M., Garcia-Bournissen F., Giglio N., Finkelstein Y. and Koren G. "Pharmacologic Treatment of Hyperthyroidism During Lactation." Canadian Family Physician. 2009. 55(8): 797-798.
  • Lawrence, Ruth A., MD, Lawrence, Robert M., MD. Breastfeeding: A Guide For The Medical Profession. 6th Edition. Mosby. 2005.

By Donna Murray, RN, BSN
Donna Murray, RN, BSN has a Bachelor of Science in Nursing from Rutgers University and is a current member of Sigma Theta Tau, the Honor Society of Nursing.