Limited evidenceVitamins & minerals

Lugol's Iodine Solution

A concentrated iodine-iodide solution that delivers milligram doses, far beyond nutritional needs. Correcting genuine iodine deficiency helps, but self-dosing Lugol's is a well-documented way to trigger thyroid dysfunction.

Evidence last reviewed: August 2026

What the science says

Correcting deficiency benefits thyroid function Moderate evidence
A systematic review and meta-analysis of iodine supplementation in mildly-to-moderately iodine-deficient pregnant women found improvements in maternal thyroid function markers, though child neurodevelopment outcomes were not clearly improved. The benefit applies to deficiency, at microgram doses.
Excess iodine causes thyroid dysfunction Strong evidence
Reviews of excess iodine intake document both iodine-induced hypothyroidism and hyperthyroidism, with risk rising sharply above the tolerable upper intake of about 1,100 µg/day in adults. A single drop of Lugol's can exceed that many times over.
Excess in pregnancy is a documented problem Moderate evidence
A systematic review and meta-analysis of excessive iodine intake in pregnancy found associations with maternal thyroid abnormalities. More is not better in this population.

Dosage & safety

Studied doseNutritional requirement is 150 µg/day for adults and 220–290 µg/day in pregnancy and lactation. Lugol's 5% supplies roughly 6 mg of iodine per drop, so it is a pharmaceutical-strength preparation and should only be used at doses set by a clinician.

SafetyCan precipitate hypothyroidism, hyperthyroidism or thyroiditis, particularly in people with nodular goitre, Hashimoto's or Graves' disease. Also causes iodine acne, metallic taste, gastrointestinal upset and, rarely, hypersensitivity. Do not self-treat thyroid conditions with it; avoid in pregnancy other than under medical supervision, and note the interaction with lithium and amiodarone.

Scientific references

Excess iodine intake: sources, assessment, and effects on thyroid function
Farebrother J, Zimmermann MB, Andersson M — Ann N Y Acad Sci, 2019
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 — Am J Clin Nutr, 2020
Prevalence of Excessive Iodine Intake in Pregnancy and Its Health Consequences: Systematic Review and Meta-analysis
Candido AC, Vieira AA, de Souza Ferreira E — Biol Trace Elem Res, 2023

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