Protocols › Iodine

Iodine in pregnancy

Goal: What trials and guidelines used to meet the higher need for iodine in pregnancy and breastfeeding.

Each protocol describes what studies used, for one goal or for one group of people. It is not advice for you: talk to a doctor before you start a supplement.

Updated 10 Nov 2026
Dose

150 to 225 µg of iodine a day in trials of pregnant women.[1][2] The American Thyroid Association advises 150 µg a day.[1]

Form

Potassium iodide tablets.[1][2]

How long

From early pregnancy until delivery.[1] In one trial, from before week 12 until 8 weeks after the birth.[2]

What studies found

In women with mild to moderate deficiency, iodine lowered thyroglobulin in most trials and in 3 trials limited the growth of the mother's thyroid. In 2 trials that tested the children, it did not change thinking, language or movement scores.[3] A 2021 review of 14 trials pooled 5 of them and found no effect on size at birth.[4] A 2017 Cochrane review found too few data for firm conclusions.[5]

Ask a doctor first

The US upper limit in pregnancy and when breastfeeding is 1,100 µg a day from all sources.[1] In a Spanish study, pregnant women who took 200 µg a day or more had a higher risk of a raised TSH.[1] In one small trial, more women had digestive problems with iodine.[5]

Ask a doctor or pharmacist first if you have a thyroid disease or take an antithyroid medicine.[1]

References

  1. Iodine: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements. ods.od.nih.gov
  2. The Effects of Iodine Supplementation in Pregnancy on Iodine Status, Thyroglobulin Levels and Thyroid Function Parameters: Results from a Randomized Controlled Clinical Trial in a Mild-to-Moderate Iodine Deficiency Area. Censi S, Watutantrige-Fernando S, Groccia G, Manso J, Plebani M, Faggian D, et al. Nutrients, 2019. PMID 31689890
  3. Systematic review and meta-analysis of the effects of iodine supplementation on thyroid function and child neurodevelopment in mildly-to-moderately iodine-deficient pregnant women. Dineva M, Fishpool H, Rayman MP, Mendis J, Bath SC Am J Clin Nutr, 2020. PMID 32320029
  4. Effects of iodine supplementation during pregnancy on pregnant women and their offspring: a systematic review and meta-analysis of trials over the past 3 decades. Nazeri P, Shariat M, Azizi F Eur J Endocrinol, 2021. PMID 33112293
  5. Iodine supplementation for women during the preconception, pregnancy and postpartum period. Harding KB, Peña-Rosas JP, Webster AC, Yap CM, Payne BA, Ota E, et al. Cochrane Database Syst Rev, 2017. PMID 28260263