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⚠ Pregnant woman using non-iodized salt (sea salt, Himalayan) — check iodine intake and supplement if needed [8]
⚠ Patient on kelp supplements with new thyroid dysfunction — check UIC and discontinue kelp [5]
⚠ Vegan patient without iodized salt or seaweed — at significant risk of deficiency [1]
⚠ Amiodarone patient with thyroid symptoms — amiodarone contains ~37% iodine by weight [2]
⚠ Child with goiter and low IQ in an iodine-deficient region — irreversible damage may have occurred; supplement and assess [3]
🥗 Food first — build your daily 150 mcg; 220 mcg pregnancy
Check the foods you regularly eat — the bar fills toward your daily target.
Seaweed (nori, 1 sheet)16 mcg
Cod (85g)99 mcg
Iodized salt (¼ tsp)71 mcg
Milk (1 cup)56 mcg
Yogurt (1 cup)75 mcg
Shrimp (85g)35 mcg
Egg (1 large)24 mcg
Cheddar cheese (28g)12 mcg
Check your regular foods above
☑ Risk checker
Residence in iodine-depleted regions (mountainous, flood-prone soils) [3]
Non-use of iodized salt (sea salt, Himalayan salt, kosher salt) [1]
Vegan diet without iodized salt or seaweed (no dairy, no seafood) [1]
Pregnancy and lactation (increased requirements) [3]
Exclusive breastfeeding by iodine-deficient mother [3]
High goitrogen consumption (cassava, millet) in iodine-marginal areas [2]
Use of non-iodized salt in processed food manufacturing [4]
Select factors
🔬 Lab interpreter
Recommended test
Urinary iodine concentration (UIC)
Urinary iodine concentration (UIC)
Reference range / target
100–199 µg/L (population median is adequate)
100–199 µg/L (population median is adequate)
When to test
Population-level surveillance. Spot UIC is unreliable for individuals due to day-to-day variation [3].
Population-level surveillance. Spot UIC is unreliable for individuals due to day-to-day variation [3].
UIC reflects recent iodine intake (past 24–48 hours). Not a useful individual marker — use median of ≥10 samples per person or use Tg [3].
Full lab monitoring ↓⚕ For professionals — confirm ranges against your local laboratory.
Clinical verdict
Iodine deficiency remains the world's most common preventable cause of intellectual disability. Universal salt iodization is the most cost-effective public health intervention. Pregnant women need 220 µg/day — the ATA recommends prenatal supplements with 150 µg iodine. Kelp supplements are dangerous due to unpredictable iodine content. Both deficiency AND excess cause thyroid dysfunction [3] [4] [5].
1 Am I deficient?
South Asia36%
Sub-Saharan Africa40%
Central Asia30%
Eastern Mediterranean25%
Europe (mild in some countries)15%
Australia / NZ (pre-fortification)12%
US (general)5%
Vegans (no iodized salt users)25%
What happens as status declines
Mild deficiency
Median UIC 50–99 µg/L (population). Subclinical hypothyroidism. Thyroid enlargement may be palpable. Cognitive impacts in children may be subtle but measurable [3].
Moderate deficiency
Median UIC 20–49 µg/L. Visible goiter. Hypothyroidism. Reduced IQ (meta-analysis: 12.5 IQ points lower in deficient vs. sufficient populations). Impaired school performance in children [3].
Severe deficiency
Median UIC <20 µg/L. Endemic goiter (>30% of population). Cretinism in offspring: irreversible intellectual disability, deaf-mutism, motor spasticity [3].
Excess iodine
UIC >300 µg/L. Paradoxical thyroid dysfunction: Jod-Basedow (iodine-induced hyperthyroidism) or Wolff-Chaikoff (iodine-induced hypothyroidism). Thyroiditis. Most common from kelp supplements, amiodarone, or contrast media [2].
Risk factors
• Residence in iodine-depleted regions (mountainous, flood-prone soils) [3]
• Non-use of iodized salt (sea salt, Himalayan salt, kosher salt) [1]
• Vegan diet without iodized salt or seaweed (no dairy, no seafood) [1]
• Pregnancy and lactation (increased requirements) [3]
• Exclusive breastfeeding by iodine-deficient mother [3]
• High goitrogen consumption (cassava, millet) in iodine-marginal areas [2]
• Use of non-iodized salt in processed food manufacturing [4]
🧬 How Iodine works ▼
2 How much do I need?
👤 Adults: Specific dosage data under clinical review
👴 Elderly: Specific dosage data under clinical review
🤰 Pregnancy: Specific dosage data under clinical review
👦 Pediatric: See guidance
Infants 0–6 months: 110 µg/day AI; children 1–3 years: 90 µg/day; 4–8 years: 90 µg/day; 9–13 years: 120 µg/day [1]. Breast milk iodine content depends on maternal status — supplementatio
🏃 Athletes: Standard dose
⚖️ Obesity: Standard dose
Fat-soluble compounds may require dose adjustment in obesity.
🩺 Renal: Consult specialist
Dose adjustment may be needed in renal impairment.
🌱 Vegan: Specific dosage data under clinical review
How to take
🍽 Timing: Can be taken at any time. Iodized salt provides consistent iodine through the day [1].
💊 With food: No specific requirement. Iodine from food and salt is well absorbed (>90%) [1].
3 Which form?
| Form | Bioavailability | Vegan | Cost |
|---|---|---|---|
| ['Potassium iodide', 'common', 'The most common supplemental form. Used in iodized salt (typically 20–40 mg KI per kg salt). Also used for thyroid protection in nuclear emergencies [1].'] | Standard | Check label | |
| ['Sodium iodide', '', 'Alternative salt form. Used in some supplements and in the Wolff-Chaikoff block protocol [2].'] | Standard | Check label | |
| ['Kelp / seaweed extracts', '', 'Natural source of iodine. Content varies enormously (16–8,165 µg per gram depending on species and origin). Kombu can contain >2,000 µg per gram — risk of excess [5]. Standardization is poor.'] | Standard | Check label | |
| ['Povidone-iodine', '', 'Topical antiseptic (not a nutritional supplement). Systemic absorption can occur through mucous membranes and large wounds — relevant in neonates and pregnancy [2].'] | Standard | Check label |
4 Common questions
Is iodized salt enough? ▼
For most people, yes. Just ½ teaspoon (3 g) of iodized salt provides approximately 100 µg of iodine — two-thirds of the adult RDA [1]. However, many people now use non-iodized salts (sea salt, Himalayan, kosher), and processed foods typically use non-iodized salt. Pregnant women may need an additional 150 µg supplement [8].
Are kelp supplements safe? ▼
Kelp iodine content is highly variable — a single capsule can contain 500–8,000+ µg, far exceeding the UL of 1,100 µg/day [5]. This can cause thyroid dysfunction. Standardized iodine supplements (potassium iodide) are much safer and more predictable. Kelp should not be used for iodine supplementation [5].
Do cruciferous vegetables cause thyroid problems? ▼
Goitrogens in cruciferous vegetables (broccoli, kale, cabbage) and soy mildly inhibit thyroid peroxidase, but this is clinically significant only in the context of concurrent iodine deficiency and massive consumption. Normal dietary amounts are safe and should not be avoided [2].
Why is iodine so critical in pregnancy? ▼
Thyroid hormones are essential for fetal brain development, especially during the first trimester when the fetus depends entirely on maternal T4. Even mild-to-moderate maternal iodine deficiency is associated with measurable IQ reduction in offspring. Severe deficiency causes cretinism — irreversible intellectual disability [3].
5 Clinical evidence
Strong
Prevention of goiter and iodine deficiency disorders through iodized salt: the most cost-effective public health intervention, eliminating endemic goiter in dozens of countries [4]. Prevention of cretinism: iodine supplementation before or during early pregnancy prevents irreversible intellectual disability in offspring [3]. Treatment of hypothyroidism caused by iodine deficiency [2]. HIGH
Moderate
Thyroid protection in nuclear emergencies: potassium iodide (130 mg for adults) saturates the thyroid, blocking radioactive iodine-131 uptake by >95% [6]. Fibrocystic breast disease: molecular iodine (I₂) at 3–6 mg/day reduced breast pain and nodularity in a randomized trial (n = 111) [7]. MODERATE
Insufficient
Cancer prevention: some ecological data link iodine intake to reduced breast and stomach cancer, but causal evidence is insufficient [2]. Cognitive enhancement in iodine-replete children: supplementation does not improve IQ beyond correcting deficiency [3]. Detox protocols involving high-dose iodine (Lugol's solution): no evidence of benefit and significant risk of thyroid dysfunction [2]. LOW
6 Safety, toxicity & adverse events
Absolute contraindications
✕ Dermatitis herpetiformis — iodine triggers flares in this gluten-sensitive skin condition
Relative
⚠ Hashimoto thyroiditis — excess iodine can worsen autoimmune thyroid destruction
⚠ Multinodular goiter — iodine excess may trigger thyrotoxicosis (Jod-Basedow effect)
⚠ Concurrent amiodarone therapy — amiodarone contains 75 mg iodine per 200 mg tablet
🚩 Red flags
● Patient taking kelp supplements with new thyroid symptoms — check TSH and discontinue kelp [5]
● Pregnant woman on non-iodized salt and no dairy — high risk of iodine deficiency affecting fetal brain [3]
● Amiodarone patient with weight loss, tremor, and tachycardia — amiodarone-induced thyrotoxicosis [2]
● Patient on 'iodine detox' protocol with Lugol's solution — excess iodine causing thyroid dysfunction [2]
● Child with goiter in an iodine-deficient region — assess and treat, but recognize cognitive damage may be irreversible [3]
7 Interactions
Drug interactions
Antithyroid drugs (methimazole, PTU) Major
Mechanism: Excess iodine can interfere with antithyroid drug efficacy by providing substrate for thyroid hormone synthesis despite enzyme blockade (escape phenomenon). [2]
Effect: Unpredictable thyroid hormone levels. Difficulty achieving euthyroid state. [2]
Action: Avoid iodine supplements and high-iodine foods during antithyroid therapy. Maintain consistent, moderate iodine intake [2].
Lithium Major
Mechanism: Both lithium and excess iodine independently inhibit thyroid hormone release. Combined use has an additive suppressive effect. [2]
Effect: Increased risk of hypothyroidism and goiter (up to 50% of lithium-treated patients develop goiter). [2]
Action: Monitor TSH every 6 months in lithium-treated patients. Avoid excess iodine supplementation [2].
Amiodarone Major
Mechanism: Amiodarone is 37% iodine by weight. A standard 200 mg daily dose delivers ~75 mg iodine — 500× the RDA. Causes both amiodarone-induced thyrotoxicosis (AIT) and hypothyroidism (AIH). [2]
Effect: AIT Type 1 (excess iodine in abnormal gland) or AIT Type 2 (destructive thyroiditis). AIH in up to 20% of patients. [2]
Action: Monitor TSH before and every 6 months during amiodarone therapy. Endocrinology referral for thyroid dysfunction [2].
ACE inhibitors (with potassium iodide) Moderate
Mechanism: Potassium from KI supplements combined with ACE inhibitor-induced potassium retention. [2]
Effect: Hyperkalemia risk, especially in renal impairment. [2]
Action: Monitor serum potassium when using KI supplements in patients on ACE inhibitors or ARBs [2].
Supplement synergies
Selenium · 55–200 µg/day selenium
Selenium is essential for thyroid deiodinase enzymes (T4→T3 conversion) and for GPx protection of the thyroid from peroxide damage. In combined deficiency, correct iodine first, then selenium [2].
Selenium is essential for thyroid deiodinase enzymes (T4→T3 conversion) and for GPx protection of the thyroid from peroxide damage. In combined deficiency, correct iodine first, then selenium [2].
Iron · As per deficiency protocol
Iron is a cofactor for thyroid peroxidase. Iron deficiency impairs thyroid hormone synthesis even when iodine is adequate [2].
Iron is a cofactor for thyroid peroxidase. Iron deficiency impairs thyroid hormone synthesis even when iodine is adequate [2].
Vitamin D · 600–2,000 IU/day
Vitamin D deficiency is associated with higher rates of autoimmune thyroid disease. Co-supplementation supports overall thyroid health [2].
Vitamin D deficiency is associated with higher rates of autoimmune thyroid disease. Co-supplementation supports overall thyroid health [2].
8 Laboratory monitoring
Urinary iodine concentration (UIC) Primary
Target: 100–199 µg/L (population median is adequate) · Population-level surveillance. Spot UIC is unreliable for individuals due to day-to-day variation [3].
Thyroglobulin (Tg) Secondary
Target: <40 µg/L in iodine-sufficient individuals
TSH and free T4 Secondary
Target: TSH 0.4–4.0 mIU/L; free T4 per lab reference
Thyroid ultrasound Secondary
Target: Normal thyroid volume for age and sex
9 Regulatory
United States (FDA): Classified as a dietary supplement. Iodized salt is voluntary (not mandatory) in the US. FDA recommends iodized salt use. UL: 1,100 µg/day [1].
European Union (EFSA): Authorized health claims for thyroid function, cognitive function, energy metabolism, nervous system function, and skin maintenance [9]. Salt iodization policies vary by country (mandatory in some, voluntary in others).
Japan (MHLW): Unique situation: high dietary iodine from seaweed (estimated 1,000–3,000 µg/day). Tolerable upper limit: 3,000 µg/day. Japanese population appears adapted to high iodine intake [2].
South Korea (MFDS): Registered health functional food ingredient. High seaweed consumption similar to Japan. Approved claims: thyroid function.
10 US supplement products
1,591
on-market products containing Iodine (NIH DSLD)
Brands carrying Iodine (424)
Click a brand to see its Iodine products.
11 Frequently paired with
12 References (9)
[1]Institute of Medicine. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academies Press; 2001. doi:10.17226/10026 REVIEW Accessed: 2026-05-29
[2]National Institutes of Health, Office of Dietary Supplements. Iodine — Fact sheet for health professionals. Updated 2024. ods.od.nih.gov REVIEW Accessed: 2026-05-29
[3]Zimmermann MB. Iodine deficiency. Endocr Rev. 2009;30(4):376-408. doi:10.1210/er.2009-0011 REVIEW Accessed: 2026-05-29
[4]World Health Organization. Salt reduction and iodine fortification strategies in public health. WHO; 2014. www.who.int GOVERNMENT Accessed: 2026-05-29
[5]U.S. Department of Agriculture. FoodData Central. fdc.nal.usda.gov GOVERNMENT Accessed: 2026-05-29
[6]Zanzonico PB, Becker DV. Effects of time of administration and dietary iodine levels on potassium iodide (KI) blockade of thyroid irradiation by 131I from radioactive fallout. Health Phys. 2000;78(6):660-667. doi:10.1097/00004032-200006000-00008 REVIEW Accessed: 2026-05-29
[7]Kessler JH. The effect of supraphysiologic levels of iodine on patients with cyclic mastalgia. Breast J. 2004;10(4):328-336. doi:10.1111/j.1075-122X.2004.21341.x REVIEW Accessed: 2026-05-29
[8]Alexander EK, et al. 2017 Guidelines of the American Thyroid Association for the diagnosis and management of thyroid disease during pregnancy and the postpartum. Thyroid. 2017;27(3):315-389. doi:10.1089/thy.2016.0457 GUIDELINES Accessed: 2026-05-29
[9]EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific opinion on the substantiation of health claims related to iodine. EFSA J. 2009;7(9):1214. doi:10.2903/j.efsa.2009.1214 GOVERNMENT Accessed: 2026-05-29
13 Related articles
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14 Cite this page
Vancouver: Pkhakadze G. Iodine — safety profile [Internet]. Tbilisi: PHIG; 2026 [cited 2026 Jun 02]. Available from: https://supplement.ge/ingredients/iodine/
APA 7th: Pkhakadze, G. (2026). Iodine — Safety profile. Public Health Institute of Georgia. https://supplement.ge/ingredients/iodine/
📋 Editorial information
Author: Prof. G. Pkhakadze, MD, MPH, PhD
Institution: Public Health Institute of Georgia (PHIG)
Affiliation: David Tvildiani Medical University (DTMU)
First published: January 2026
Last reviewed: 2026-05-29
Next review: December 2026
References: 9 cited sources
COI: SupplementIndex receives no funding from supplement manufacturers. All content independently authored by PHIG.
Process: Systematic literature review
📄 License & reuse
Published under Creative Commons Attribution 4.0 International (CC BY 4.0). You may share and adapt for any purpose with attribution.
Pkhakadze G. "Iodine — Safety Profile." SupplementIndex, PHIG, 2026. https://supplement.ge/ingredients/iodine/ CC BY 4.0.
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Educational and public health purposes. CC BY 4.0. Consult your healthcare provider before starting any supplement. Corrections: info@accreditation.ge. Publisher: PHIG