Iodine

Iodine supplementation · Potassium Iodide · Molecular Iodine

Snapshot

Indications	Contraindications
Iodine deficiency¹ Childhood cognition² Hypothyroidism prevention in children² Fibrocystic breast symptoms¹ Radiation thyroid protection¹	Potassium-sparing diuretics¹ Autoimmune thyroid disease¹

Iodine is a trace element used to make thyroid hormones, which regulate metabolism and fetal and infant nervous system development¹. Supplementation is used to prevent deficiency, which causes goiter, hypothyroidism, and impaired neurodevelopment, and to meet higher needs in pregnancy and lactation¹. It is also used for childhood cognition and, with thinner support, fibrocystic breast symptoms and immune function¹. Vegans and people avoiding dairy, seafood, and eggs face the lowest intake^3–5.

In pregnancy, a Cochrane review found too little data to judge routine supplementation. In a 2024 prospective cohort of pregnant women, child cognitive and language scores were lowest at both low and high maternal iodine intakes, with supplements driving the high intakes⁶. Products list iodine mostly as potassium iodide, sodium iodide, or kelp; see Form comparison¹.

The most consequential caution is thyroid dysfunction, because people with autoimmune thyroid disease or past deficiency can react to intakes considered safe for others¹. Per the National Institutes of Health fact sheet, people taking certain medications regularly are asked to discuss iodine intake with their health care providers¹.

Last updated October 16, 2026. Read how we make monographs.

In the full monograph

72 sources, 59 studies

When to useThe situations practitioners use it for, each with the reason and the study behind it.
SafetyWho should avoid it, who needs extra care, and the side effects reported in studies.
InteractionsThe medicines and supplements it interacts with, the effect of each, and what labeling says to watch.
Protocol notesThe doses used in studies, how and when they were taken, and how the forms on the market compare.
How it worksWhat it is and how it works in the body, in plain terms.
Published studiesThe studies behind each use, popular claims checked against them, and trials still under way.
Word of mouthWhat patients and practitioners report online, kept separate from the clinical evidence.
Clinical perspectiveA closing read of where the evidence is solid, where it is thin, and what has not been studied.

Snapshot

In the full monograph

Sources