Trace minerals
Iodine
Thyroid hormones
Thyroid hormone (T3/T4) synthesis.
Upper-limit caution
The Tolerable Upper Intake Level for Iodine is 1100 mcg per day. Routine intakes above this level — counting food + supplements — raise the risk of adverse effects. Multivitamins, fortified foods, and standalone supplements stack faster than people expect.
What Iodine does
Iodine has one job in humans — synthesis of the thyroid hormones T3 and T4 — and its absence causes the most preventable cause of intellectual disability worldwide. Universal salt iodization eliminated endemic goiter and cretinism in most developed countries by the mid-20th century. Two trends in wealthy countries are quietly reintroducing risk: artisan/sea/Himalayan salts that aren't iodized, and dairy reduction (milk is a major source through iodophor sanitization residues and iodine-supplemented animal feed).
Food sources of Iodine
Approximate Iodine content per serving. Whole-food intake counts toward your daily total alongside any supplemental dose.
| Food | Serving | Iodine |
|---|---|---|
| Kelp (dried) | 1 g | 15–3,000 mcg (highly variable) |
| Cod (cooked) | 3 oz | 100 mcg |
| Iodized salt | 1/4 tsp | 75 mcg |
| Milk | 1 cup | 85 mcg |
| Egg (whole) | 1 large | 25 mcg |
| Plain yogurt | 1 cup | 75 mcg |
Signs of Iodine deficiency
- ●Goiter (visible thyroid enlargement)
- ●Hypothyroidism: fatigue, weight gain, cold intolerance, dry skin, hair loss
- ●In pregnancy: maternal hypothyroidism, intellectual disability and cretinism in offspring
- ●Children: growth and cognitive delay
Who needs more Iodine
Groups and situations where Iodine requirements rise or status commonly runs low:
- ●Pregnancy and lactation — RDA rises to 220 and 290 mcg
- ●Vegan and dairy-free diets without iodized salt or sea vegetables
- ●Habitual use of artisan, kosher, sea, or pink salts (most are not iodized)
- ●Living in iodine-deficient regions (mountainous, glaciated soil)
How Iodine appears on labels
Supplement labels list Iodine under several names depending on the chemical form used. Any of these on an ingredients panel counts toward your Iodine intake:
- iodine
- potassium iodide
- kelp
Best supplements for Iodine
Top-scoring supplements in our catalog that list Iodine on the label. Each product is graded on Formulate's ingredient-level rubric — dose accuracy, form, transparency, and third-party testing.
Deep dive
For mechanism of action, dosing protocols, evidence grade, and interaction warnings on Iodine, see the full encyclopedia entry:
Bladderwrack encyclopedia entry →Guides covering Iodine
Long-form articles in our guide library that go deeper on Iodine — comparisons, protocols, and reviews.
Frequently asked questions
What is the daily target for Iodine?
What foods are highest in Iodine?
What is the best form of Iodine to supplement?
What are the signs of Iodine deficiency?
Who is most at risk for low Iodine?
Related trace minerals
Track your full intake
Formulate's free web app aggregates Iodine (and ~40 other nutrients) across every supplement in your stack — flagging underdoses, overlaps, and upper-limit overshoots in one view.
Track your intake free →Medical disclaimer. This page is educational and does not replace advice from a qualified healthcare provider. Targets and upper limits are general adult reference values; individual needs vary by age, sex, pregnancy status, and clinical context.