Potassium iodide

Iodine therapy for thyroid function

ATC code: H03CA01 (Potassium iodide)

Brand names – drugs

Iosat, Thyrosafe, ThyroShield

Brand names – supplements

Solgar Kelp

Supplements are not tested in clinical trials and are not registered as medications.

Mechanism of action

Potassium iodide is the standard preparation for stable iodine supplementation. Iodine is an essential substrate for thyroid hormone (T3, T4) synthesis. At physiological doses (100–200 µg), it corrects deficiency and supports normal hormone synthesis. At pharmacological doses (above 30 mg), it suppresses thyroid hormone secretion via the Wolff-Chaikoff effect and blocks thyroid uptake of radioactive iodine-131.

Indications

Iodine deficiency disorders

First line

Potassium iodide 100–200 µg daily is first-line prevention and treatment of iodine deficiency disorders. recommends universal salt iodisation as foundational population prevention. Individual supplementation is indicated in children, adolescents, and people not consuming iodised salt in regions of mild-to-moderate iodine endemicity. Russian Ministry of Health guidelines include potassium iodide as a required component of IDD prevention.

Sources

Iodine prophylaxis in pregnancy and lactation

First line

Potassium iodide 200 µg daily in pregnant and lactating women is first-line prevention of iodine deficiency, maternal hypothyroidism, and foetal neuropsychological developmental disorders. 2017 gives a level A recommendation for routine iodine supplementation in populations with sub-adequate intake. Russian clinical guidelines support routine supplementation in the country's mild-to-moderate iodine endemicity.

In baseline autoimmune thyroid disease (AIT with antibodies) or after radioactive iodine treatment, doses are individualised with an endocrinologist.

Sources

Thyroid radiation protection in nuclear emergencies

First line

Potassium iodide at high dose (130 mg adult, 65 mg children 3–18 years, 32 mg children 1 month – 3 years) as a single dose or repeated courses when radioactive iodine-131 enters the environment is the only specific intervention for thyroid protection. 2017 gives a clear protocol on doses and timing. Justified only on official authorities' direction during a nuclear emergency. Self-administered “prophylactic” use without an emergency is useless and dangerous.

Sources

Marketing claims without evidence base

The drug is promoted for these uses outside international guidelines. Each entry below is analyzed against AEMPS, FDA, EMA, Cochrane and major RCTs.

Anti-aging and longevity

Not recommended

Potassium iodide is a source of iodine prescribed for iodine deficiency prevention, hypothyroidism in iodine-deficient populations, and thyroid blockade in nuclear emergencies. In anti-aging communities, potassium iodide is sold to slow aging and extend life, often combined with other detox protocols. In areas with adequate iodine intake (most developed countries use iodized salt), additional iodine is unnecessary; international guidelines do not mention potassium iodide as an anti-aging agent. Iodine overdose causes iodine-induced hyperthyroidism (especially in older adults with nodular goiter) or, paradoxically, hypothyroidism (the Wolff-Chaikoff effect). If potassium iodide is being taken for longevity, consider seeking a second opinion.

Sources

ATA: Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum (2017)

Practical notes

Timing and administration

Take regardless of meals. Iodomarin and Iodbalance are 100 and 200 µg tablets for daily supplementation. Potassium iodide 130 mg (for radiation protection) – on official authorities' direction during a nuclear emergency.

Dose titration

Iodine RDA: children under 5 – 90 µg, 6–12 years – 120 µg, adults – 150 µg, pregnant and lactating – 200–250 µg. Prophylactic supplementation: 100–200 µg daily. Radiation protection: single 130 mg dose for adults. Upper tolerable intake level (UL): 1,100 µg daily.

Monitoring

No special monitoring is needed during long-term therapy at physiological doses. In patients with nodular goitre, autoimmune thyroiditis, or prior thyrotoxicosis, assess TSH, free T4, and thyroid ultrasound before starting supplementation. Long-term: TSH every 6–12 months. With hyperthyroid symptoms, immediate discontinuation and endocrinologist consultation.

Food and drinks

Dietary iodine sources: iodised salt (5 g salt = 150 µg iodine), marine fish, seafood, sea vegetables (kelp, nori). Iodised salt is the most effective population-level intervention. In regions with mass salt iodisation and daily iodised salt use, individual supplementation may not be required. In most Russians, dietary iodine intake is below recommended – supplementation at 100–200 µg daily is reasonable.

Common myths

Myth: “iodine should be taken in 2-month courses with breaks”. Fact: the thyroid uses iodine continuously. Cyclical use with breaks has no physiological basis. Supplementation is continuous or not at all.

Myth: “iodine drops on sugar – a folk method”. Fact: skin iodine grids and oral iodine drops are not effective iodine supplementation methods. Iodine dose in these approaches cannot be assessed. Use only certified preparations with a known dose.

Myth: “iodine panic – buy iodine urgently after nuclear accident news”. Fact: high-dose potassium iodide (130 mg) is used only on official authorities' direction with proven release of radioactive iodine-131. Without such direction, use is useless and dangerous – it causes iodine-induced hyperthyroidism in some patients.

Drug–nutrient interactions

Selenium

Selenium is a cofactor for iodothyronine deiodinase, the enzyme converting T4 to active T3. In combined iodine and selenium deficiency, iodine supplementation efficacy is reduced. In patients with autoimmune thyroiditis, additional selenium use is discussed with an endocrinologist.

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Official sources

Direct links to regulator labels. Open in a new tab.

FDA / DailyMed

FDA — DailyMed Drug Labels

Label dated: 05/28/2025

GRLS

Russian State Register of Medicines

Safety

Contraindications

Hyperthyroidism of any aetiology
Nodular and multinodular toxic goitre
Dermatitis herpetiformis (Duhring disease)
Pulmonary tuberculosis (at high doses)
Iodine hypersensitivity
Thyroid adenoma (for physiological doses – relative)

Serious adverse effects

Iodine-induced hyperthyroidism (Jod-Basedow phenomenon) in patients with latent thyroid disease
Development or worsening of autoimmune thyroiditis in predisposed patients
Anaphylactic reactions (very rare)

Common adverse effects

Metallic taste
Epigastric discomfort
Skin redness and itching

Uncommon adverse effects

Iodism: rhinitis, conjunctivitis, bronchitis at high doses
Acne
Skin rash

PregnancyFDA A

FDA category A at physiological doses. Supplementation at 200–250 µg daily during pregnancy and lactation is encouraged by international societies. High doses (above 500 µg daily) can cause foetal hypothyroidism and are not recommended.

Breastfeeding

Actively secreted into breast milk. Maternal supplementation at 250 µg daily ensures adequate infant iodine. High-dose potassium iodide for maternal radiation protection requires temporary breastfeeding cessation.

Calculate RID

Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.

Frequently asked

What is Potassium iodide used for?

Potassium iodide is evaluated for the following indications with varying evidence strength: Thyroid radiation protection in nuclear emergencies (evidence tier A), Iodine prophylaxis in pregnancy and lactation (evidence tier A), Iodine deficiency disorders (evidence tier A). See the full indication matrix with dosing and citations above on this page.

What are the side effects of Potassium iodide?

Common side effects of Potassium iodide (≥ 1 in 100): Metallic taste, Epigastric discomfort, Skin redness and itching. See the Safety section for uncommon and serious reactions.

Is Potassium iodide safe during pregnancy?

FDA category A. FDA category A at physiological doses. Supplementation at 200–250 µg daily during pregnancy and lactation is encouraged by international societies. High doses (above 500 µg daily) can cause foetal hypothyroidism and are not recommended.

Is Potassium iodide compatible with breastfeeding?

Who should not take Potassium iodide?

Potassium iodide is contraindicated in: Hyperthyroidism of any aetiology; Nodular and multinodular toxic goitre; Dermatitis herpetiformis (Duhring disease); Pulmonary tuberculosis (at high doses); Iodine hypersensitivity. Full list in the Safety section.

“iodine should be taken in 2-month courses with breaks”

the thyroid uses iodine continuously. Cyclical use with breaks has no physiological basis. Supplementation is continuous or not at all.

“iodine drops on sugar – a folk method”

skin iodine grids and oral iodine drops are not effective iodine supplementation methods. Iodine dose in these approaches cannot be assessed. Use only certified preparations with a known dose.

“iodine panic – buy iodine urgently after nuclear accident news”

high-dose potassium iodide (130 mg) is used only on official authorities' direction with proven release of radioactive iodine-131. Without such direction, use is useless and dangerous – it causes iodine-induced hyperthyroidism in some patients.

Mechanism of action

Practical notes

Timing and administration

Dose titration

Monitoring

Food and drinks

Common myths

Safety

Contraindications

Hyperthyroidism of any aetiology
Nodular and multinodular toxic goitre
Dermatitis herpetiformis (Duhring disease)
Pulmonary tuberculosis (at high doses)
Iodine hypersensitivity
Thyroid adenoma (for physiological doses – relative)

Serious adverse effects

Iodine-induced hyperthyroidism (Jod-Basedow phenomenon) in patients with latent thyroid disease
Development or worsening of autoimmune thyroiditis in predisposed patients
Anaphylactic reactions (very rare)

Common adverse effects

Metallic taste
Epigastric discomfort
Skin redness and itching

Uncommon adverse effects

Iodism: rhinitis, conjunctivitis, bronchitis at high doses
Acne
Skin rash

PregnancyFDA A

Breastfeeding

Calculate RID

Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.

Frequently asked

What is Potassium iodide used for?

What are the side effects of Potassium iodide?

Common side effects of Potassium iodide (≥ 1 in 100): Metallic taste, Epigastric discomfort, Skin redness and itching. See the Safety section for uncommon and serious reactions.

Is Potassium iodide safe during pregnancy?

Is Potassium iodide compatible with breastfeeding?

Who should not take Potassium iodide?

“iodine should be taken in 2-month courses with breaks”

the thyroid uses iodine continuously. Cyclical use with breaks has no physiological basis. Supplementation is continuous or not at all.

“iodine drops on sugar – a folk method”

skin iodine grids and oral iodine drops are not effective iodine supplementation methods. Iodine dose in these approaches cannot be assessed. Use only certified preparations with a known dose.

“iodine panic – buy iodine urgently after nuclear accident news”