How much iodine do you need during pregnancy?
The World Health Organization recommends 250 mcg of iodine a day in pregnancy and while breastfeeding. The US target is 220 mcg in pregnancy and 290 mcg while breastfeeding. The American Thyroid Association advises a daily supplement with 150 mcg of iodine (as potassium iodide), plus iodized salt at home. Many prenatals contain no iodine, so check your label.
On this page
The numbers
| Who says | Pregnancy | Breastfeeding |
|---|---|---|
| World Health Organization | 250 mcg a day | 250 mcg a day |
| US recommended amount | 220 mcg a day | 290 mcg a day |
| American Thyroid Association | 150 mcg supplement daily (as potassium iodide), also when planning | 150 mcg supplement daily |
| American Academy of Pediatrics | At least 150 mcg supplement, plus iodized salt | At least 150 mcg supplement, plus iodized salt |
For comparison, other adults need 150 mcg. So your need rises by a lot. WHO notes there's no added benefit above 500 mcg a day, and the safe upper limit for adults is 1,100 mcg a day (900 mcg for pregnant teens under 19). The goal is enough, not more.
Why the baby's brain depends on your iodine
Iodine is part of thyroid hormone, and thyroid hormone is needed for the baby's brain and nervous system to develop. Early in pregnancy, your baby can't make its own thyroid hormone yet and depends entirely on yours. In the first trimester, your iodine is your baby's iodine.
WHO staff have called iodine deficiency "the world's greatest single cause of preventable brain damage in childhood." Severe deficiency is rare in North America. The open question is what a mild shortfall does.
In the UK's ALSPAC study, 67% of 1,040 pregnant women had low iodine in early pregnancy, and low iodine was linked with their children being more likely to score in the bottom quarter for verbal IQ at age 8 (odds ratio 1.58) and for reading at age 9 (odds ratio 1.69). That's a link, not proof. A randomized trial that gave iodine supplements to 832 mildly low pregnant women in India and Thailand found no difference in their children's IQ at age 5 to 6, so aim for enough iodine rather than expecting a pill to raise IQ.
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Are you getting enough?
Maybe not. In US national surveys, the typical iodine level in pregnant women's urine fell from 181 mcg/L in 2003-2004 to 144 mcg/L in 2007-2014. WHO calls 150 to 249 mcg/L adequate in pregnancy. The typical pregnant woman now sits right at the line.
Dairy matters more than most people realize. Pregnant women who'd had no dairy in the past 24 hours had a typical urine level of just 100 mcg/L. Soy and almond drinks contain only small amounts of iodine, so if you've switched to plant milk, pay extra attention. Location doesn't protect you either. The UK's NHS pregnancy vitamin advice doesn't recommend an iodine supplement, yet two-thirds of the ALSPAC mothers were low. Wherever you live, don't assume someone has already checked your iodine.
The sea-salt trap. Sea salt, pink Himalayan salt and kosher salt are usually not iodized. And most of the salt Americans eat comes from processed foods, which almost always use non-iodized salt. So eating salty food doesn't mean you're getting iodine. The fix isn't more salt: keep a shaker of iodized salt for the salt you already add at home. A quarter teaspoon has about 78 mcg.
Iodine foods at a glance
| Food | Serving | Iodine (mcg) |
|---|---|---|
| Cod, baked | 3 oz | 146 |
| Greek yogurt, plain nonfat | 3/4 cup | 87 |
| Nonfat milk | 1 cup | 84 |
| Iodized table salt | 1/4 tsp | 78 |
| Egg, hard-boiled | 1 large | 31 |
| Tuna, canned in water | 3 oz | 7 |
Some US bread is made with an iodate dough conditioner, and two slices can carry about 296 mcg. Check the ingredients for "iodate" or "iodized salt." Eggs add a little iodine along with their choline; see eggs in pregnancy.
Go easy on seaweed. Commercial seaweeds range from 16 to 2,984 mcg of iodine per gram, so one gram of the strongest kind can carry more than twice the adult upper limit. Too much iodine can make the thyroid slow down or speed up. A sprinkle of nori or a cooked or veggie sushi roll is fine (see sushi in pregnancy). Skip kelp supplements and kelp powders unless your doctor says otherwise.
Check your prenatal
Many prenatals have no iodine. In a look at 59 best-selling US prenatals, only 34 (about 58%) contained it. In a 2025 lab test of 47 US prenatals, 53% listed iodine, and only 4 of those actually contained the amount on the label. Turn your bottle over and look for "iodine (as potassium iodide)." Our prenatal label checklist covers the other lines worth checking.
If yours has none, ask your doctor what to do. This matters most if you have a thyroid condition, because people with thyroid disease can react to iodine amounts that are fine for others.
Start early if you can
Your thyroid stores iodine and seems to like a slow fill. In a study of 433 pregnant women in Sicily, women who had used iodized salt for more than two years before pregnancy were much less likely to have low thyroid hormone. Women who started a 150 mcg supplement only in early pregnancy were also protected, but many had a temporary jump in TSH. The authors advised starting iodine several months before conception. If you're already pregnant, start now; it's still the right move.
Do this
- Swap your kitchen salt for iodized salt, and use it for the salt you already add.
- Check your prenatal for "iodine (as potassium iodide)" and note the amount.
- Keep dairy, eggs or low-mercury fish like cod in your week if you eat them.
- Skip kelp supplements and kelp powders unless your doctor recommends them.
- Ask your doctor about iodine if your prenatal has none or you have a thyroid condition.
When to ask your doctor
Check with your doctor or midwife first if…
- You have a thyroid condition or take thyroid medicine.
- You're thinking about kelp or seaweed supplements.
- You're under 19, since the safe upper limit is lower (900 mcg a day).
Call your doctor now if…
- You can't keep food or fluids down for 24 hours.
- You have vaginal bleeding, fluid leaking or severe belly pain (call your doctor or 911 now).
- You have a racing or pounding heartbeat or chest pain (call your doctor or 911 now).
This page is general information, not medical advice. Every pregnancy and every child is different. Ask your doctor, midwife or pediatrician before changing supplements, diet or care.
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In the book: Chapter 7: First Trimester: The Foundation Weeks
Chapter 7 explains why your thyroid runs the baby's early brain work, with the full iodine food list, the seaweed limits and a label check, and The Prenatal Label Decoder puts every brain nutrient's target on one page.
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People also ask
Does sea salt have iodine?
Usually not. Sea salt, pink Himalayan salt and kosher salt are usually not iodized. Iodized table salt is. Keep an iodized shaker for the salt you add at home; a quarter teaspoon has about 78 mcg of iodine. You don't need to eat more salt.
Can you get too much iodine in pregnancy?
Yes. The safe upper limit for adults is 1,100 mcg a day, and WHO sees no extra benefit above 500 mcg. Seaweed is the usual culprit, since some kinds carry thousands of micrograms per gram. Skip kelp supplements unless your doctor says otherwise.
Do I need iodine if I eat dairy?
Dairy helps a lot: a cup of nonfat milk has about 84 mcg. But US surveys show the typical pregnant woman sits right at the edge of enough. The American Thyroid Association still advises a 150 mcg supplement daily in pregnancy. Ask your doctor what's right for you.
Does iodine affect my baby's brain?
Yes. Your baby's brain needs thyroid hormone, and early in pregnancy your baby relies entirely on yours, which your thyroid makes from iodine. Low iodine in pregnancy is linked to lower verbal and reading scores in children. The goal is enough, not more: WHO sees no extra benefit above 500 mcg a day.