Iodine is a mineral your body uses to make thyroid hormones. In pregnancy, those hormones help your baby’s brain and nervous system develop, and early on your baby depends entirely on your supply. Some pregnant women in the U.S. may not get quite enough, and not every prenatal vitamin includes iodine.

The short version

  • How much: 220 micrograms (mcg) a day during pregnancy and 290 mcg while breastfeeding, up from 150 mcg before pregnancy, according to the NIH.
  • Where it comes from: iodized salt, dairy, eggs, and seafood. Fruits, vegetables, rice, and beans have little or none.
  • Prenatal vitamins: the American Thyroid Association recommends a daily supplement with 150 mcg of iodine for women who are pregnant, planning a pregnancy, or breastfeeding, and the American Academy of Pediatrics recommends at least 150 mcg. Check your label, because many prenatals leave it out.
  • More isn’t better: the upper limit is 1,100 mcg a day (900 mcg for teens). Kelp and some iodine-only supplements can go well above it.
  • Thyroid conditions: if you have one, ask your provider before taking an iodine supplement.

What iodine does in pregnancy

Iodine is part of the thyroid hormones T4 and T3. They control how your body uses energy, and they’re needed for normal bone and nervous system development in a fetus and an infant, according to the NIH. In early pregnancy, before your baby’s own thyroid is fully formed, your baby relies on your thyroid hormone. Your body makes about 50% more of it during pregnancy, which takes more iodine.

What happens if you don’t get enough

  • Severe deficiency is rare in the U.S. When it happens in pregnancy, it can cause major problems with a baby’s brain development and growth, and it raises the risk of miscarriage and stillbirth.
  • Mild to moderate shortfalls are the more common concern. A combined analysis of 6,180 mothers and children from three European studies found lower verbal IQ scores in children whose mothers had lower iodine levels in the first trimester. One study also linked mild to moderate deficiency to a higher risk of ADHD in children.
  • What isn’t settled: two randomized trials gave women 150 or 200 mcg of iodine a day from early pregnancy and found no effect on their children’s thinking, language, or movement scores at ages 1.5 to 2. The NIH calls the evidence on iodine supplements for child development inconclusive.

So the link between low iodine and development is real, but we don’t yet know how much a shortfall in a U.S. pregnancy matters, or how much a supplement changes the outcome.

How much you need

These amounts come from the NIH and count iodine from food, drinks, and supplements together.

Stage Daily need Upper limit
Women 19 and older, not pregnant 150 mcg 1,100 mcg
Teens 14 to 18, not pregnant 150 mcg 900 mcg
Pregnant 220 mcg 1,100 mcg (900 mcg for ages 14–18)
Breastfeeding 290 mcg 1,100 mcg (900 mcg for ages 14–18)

The World Health Organization recommends a slightly higher 250 mcg a day for pregnancy and breastfeeding.

Do women get enough?

Pregnant women in the U.S. get a median of about 216 mcg of iodine a day from food, according to national survey data from 2017 to 2020. With supplements counted, the median rises to 235 mcg, and about 1 in 10 still falls below the average requirement. Urine tests show a bigger gap:

  • In those surveys, pregnant women had a median urine iodine level of 131 mcg/L, and 63% were below 150 mcg/L, the level the World Health Organization considers adequate in pregnancy.
  • In earlier survey data, pregnant women who ate no dairy in the past day had a median of 100 mcg/L, compared with 163 for women who did.
  • Women who limit their salt also tend to have lower iodine levels.

The NIH notes that the effect of this shortfall on babies isn’t known. It also says urine tests are meant to describe groups of people, so they aren’t a reliable way to check one woman’s iodine status.

Where to get it

Food

These amounts come from the NIH. The Daily Value for iodine is 150 mcg.

Food and serving Iodine (mcg)
Cod, baked, 3 ounces 146
Seaweed (nori), dried, 2 tablespoons flaked 116
Oysters, cooked, 3 ounces 93
Greek yogurt, plain, nonfat, ¾ cup 87
Milk, nonfat, 1 cup 84
Iodized table salt, ¼ teaspoon 78
Fish sticks, cooked, 3 ounces 57
Egg, hard-boiled, 1 large 31
Ice cream, chocolate, ⅔ cup 28
Cheddar cheese, 1 ounce 14
Shrimp, cooked, 3 ounces 13
Tuna, canned in water, 3 ounces 7
Chicken breast, 3 ounces 1
Banana, broccoli, rice, green peas, or lima beans 0

A few details that change the numbers:

  • Milk varies a lot. One study of nonfat milk found 38 to 160 mcg per cup, depending on how the dairy was run.
  • Bread depends on the brand. Some bread is made with a dough conditioner that contains iodine, which can add nearly 300 mcg in 2 slices. Only about 20% of bread products list it, and most bread has almost none. The Nutrition Facts label doesn’t have to show it.
  • Soy and other plant drinks have very little iodine. A cup of soy drink has about 3 mcg.
  • Seaweed ranges from 16 to nearly 3,000 mcg per gram, depending on the type, so it’s hard to know how much you’re getting.

Iodized salt

Iodized salt is a main source. Table salt labeled “iodized” has about 45 mcg of iodine per gram. But most of the salt in packaged and restaurant food isn’t iodized, and sea salt, kosher salt, and Himalayan salt usually aren’t either. Check that the salt you cook with says “iodized.”

Putting a day together

A day Iodine
1 cup nonfat milk, ¾ cup Greek yogurt, 1 egg, and ¼ teaspoon iodized salt 280 mcg
The same day with non-iodized salt 202 mcg
Mostly plant foods with no seaweed or iodized salt Close to 0

The first day clears the 220 mcg target. The second falls just short, which is how a healthy diet can still come up low. If you limit your salt, dairy, eggs, and fish matter more, and so does a prenatal with iodine.

Prenatal vitamins and iodine

The American Thyroid Association recommends that women who are planning a pregnancy, pregnant, or breastfeeding take 150 mcg of iodine a day as potassium iodide. The American Academy of Pediatrics recommends at least 150 mcg a day plus iodized salt. Both recommendations are summarized by the NIH.

Prenatal vitamins don’t always follow that advice:

  • In a 2021 review of 188 prenatal vitamins on the U.S. market, 76% contained iodine, with a median of 150 mcg per serving. That leaves about 1 in 4 with none.
  • In national survey data from 2011 to 2014, only about 1 in 6 pregnant women who took any supplement took one with iodine.

Look for “iodine” or “potassium iodide” on the Supplement Facts panel, with an amount near 150 mcg. See Prenatal Vitamin Questions, Answered.

Too much iodine, thyroid conditions, and medicines

Too much can cause the same problems as too little. High intakes can cause goiter (an enlarged thyroid), an underactive thyroid, an overactive thyroid, and thyroid inflammation, according to the NIH. Some people, including those with autoimmune thyroid disease, can have problems at amounts that are safe for most people.

Stick with the usual dose. In one Spanish study, pregnant women who took 200 mcg or more of supplemental iodine a day were more likely to have a high TSH level (a sign the thyroid is struggling) than women who took less than 100 mcg. The NIH says more research is needed, and notes that both low and high iodine intakes in pregnancy have been linked to developmental problems in children. That’s one reason not to go above the amount your prenatal contains.

Be careful with kelp. Seaweed and kelp supplements vary enormously in iodine, and iodine-only supplements sometimes contain more than the upper limit. Ask your provider before taking either.

Tell your provider about your thyroid and your medicines. If you have a thyroid condition, ask before taking any iodine supplement. High doses can also interact with antithyroid medicines such as methimazole, and potassium iodide can raise potassium levels when taken with ACE inhibitors or potassium-sparing diuretics, according to the NIH.

If you eat seafood, ACOG advises avoiding raw or undercooked fish and shellfish during pregnancy. Cooked cod, shrimp, and fish sticks all count toward your iodine.

What to do now

  • Check your prenatal vitamin for iodine, ideally about 150 mcg as potassium iodide.
  • Check that the salt you cook with says “iodized.”
  • Add iodine foods you already like: milk, yogurt, eggs, or cooked fish.
  • If you eat little or no dairy, eggs, or seafood, ask your provider whether your prenatal has enough.
  • Skip kelp supplements unless your provider recommends them.
  • If you have a thyroid condition, ask your provider about iodine before changing anything.

Related reading

Sources

Updated November 2026. This article is for general information and is not a substitute for advice from your health care provider.