Iodine
Also known as: Potassium iodide, Kelp-derived iodine
Iodine is an essential nutrient required for normal thyroid function, and in many places it is supplied through iodized salt, dairy, and seafood. It is genuinely essential, but it has a notably narrow window: both insufficient and excessive intakes can affect the thyroid. For this reason, iodine supplementation, thyroid conditions, and thyroid medications are closely intertwined, and decisions here are best made with a qualified healthcare professional rather than self-directed.
Snapshot
What this page can tell you: NIH ODS figures for iodine's upper limit, that both too little and too much affect the thyroid, and its medication interactions.
What it cannot: That iodine treats a thyroid condition, or your personal need — both deficiency and excess affect the thyroid. Informational only.
🧩 Stack insights — how this fits into a schedule
Thyroid — both too little and too much — NIH ODS: both too little and too much iodine can affect the thyroid — high intakes can cause goiter and thyroid inflammation. The adult upper limit is 1,100 mcg/day. If you have a thyroid condition, review iodine with a clinician; this is not a thyroid treatment.
No thyroid treatment or effect is claimed here.
Antithyroid drugs; ACE inhibitors / K-sparing diuretics — NIH ODS: iodine may interact with antithyroid drugs (e.g. methimazole), and potassium iodide with ACE inhibitors or potassium-sparing diuretics can raise blood potassium. Worth reviewing with a clinician or pharmacist if any apply.
Relationship insights are informational only — they describe what is commonly discussed or studied, not what you should take. Not medical advice; review your routine with a clinician or pharmacist.
🧭 How iodine caution scales with the amount
| Amount | Caution level | Note |
|---|---|---|
| Common label amount (~150 mcg) | Low–Moderate | Around the adult daily need; kelp products can be highly variable. |
| At/above the upper limit (1,100 mcg/day) | High | NIH ODS adult UL; high intakes can cause goiter and thyroid inflammation. |
Both too little and too much affect the thyroid. Official figures, not a personal recommendation.
🕒 Timing
When: With a meal
Food: With food
Commonly taken with food; timing is otherwise flexible.
💊 Common use range
150 mcg
A commonly cited adult upper limit is around 1,100 mcg/day from all sources — verify this figure; kelp-based products can deliver highly variable, sometimes excessive amounts.
Ranges are informational, not a recommended dose. Talk to a professional about what is right for you.
🤔 Worth considering?
Evidence vs. effort: Moderate evidence relative to burden
Essential in the right amount, but both too little and too much can affect the thyroid. People with thyroid conditions or on thyroid medication should be especially careful and discuss iodine with a healthcare professional.
A general summary, not a recommendation. Whether something fits your situation is worth discussing with a healthcare professional.
⚠️ Commonly noted interactions (supplements)
None listed.
Often about absorption or timing rather than danger — separating doses is common. This list is not exhaustive.
🧭 Caution level
Ask a clinician or pharmacist before use.
- Thyroid caution category
- Pregnancy / breastfeeding caution
- Mineral spacing considerations
- Narrow margin — easy to exceed the upper limit at higher doses
- Higher caution if you take thyroid medication (space doses apart)
- Higher caution if you have a thyroid condition
Caution level is an informational summary of commonly discussed caution categories and doses — not a safety rating, approval, or medical advice. Low caution does not mean safe for you.
🩺 Medication caution categories
- Thyroid medication
- Thyroid conditions (health condition)
- Pregnancy or nursing (health condition)
🏥 Surgery & procedure caution
Not a well-established surgical concern; share your full supplement list with your care team.
If you have a procedure scheduled, bring your full supplement list to your surgical and anesthesia team. Do not stop prescribed medication unless your clinician tells you to. Do not start or stop supplements based only on this app.
✅ Quality checklist
- Prefer products with third-party testing or a certificate of analysis (COA) — commonly recommended for this ingredient.
- Commonly discussed quality checks: Heavy metals, Label accuracy.
- Check the label for the exact form and the elemental or active amount per serving.
🧩 Commonly paired with
🔁 Alternatives
🗣️ Questions for a professional
- Given my thyroid health or medication, is supplemental iodine safe, and at what amount?
🛡️ Safety notes (source-reviewed)
- NIH ODS adult upper limit: 1,100 mcg/day.
- Both deficiency and excess can affect the thyroid (goiter, inflammation).
- Interactions: antithyroid drugs (methimazole); potassium iodide with ACE inhibitors or potassium-sparing diuretics can raise blood potassium.
⚖️ Evidence limitations
- Kelp/seaweed iodine content is highly variable; this page makes no thyroid-treatment claim.
❓ Frequently asked
Can you take too much iodine?
Yes. NIH ODS sets a 1,100 mcg/day adult upper limit, and high intakes can cause goiter and thyroid inflammation — the same direction as deficiency in some ways. If you have a thyroid condition, review iodine with a clinician.
Does iodine interact with medications?
NIH ODS notes interactions with antithyroid drugs, and potassium iodide with ACE inhibitors or potassium-sparing diuretics can raise blood potassium. A pharmacist can confirm.
🔬 Evidence snapshot
An essential nutrient for thyroid function. Supplementation clearly benefits iodine-deficient people; evidence for supplementing when intake is already adequate is inconclusive.
🚦 Commonly noted cautions (auto)
Thyroid caution category. This item carries a thyroid caution category. If you have a thyroid condition or take thyroid medication, consider discussing it with a healthcare professional. This is a general caution, not a diagnosis or medical instruction.
Pregnancy / nursing caution category. This item carries a pregnancy/nursing caution category. If you are pregnant, nursing, or planning pregnancy, consider discussing it with a healthcare professional. This is a general caution, not a diagnosis or medical instruction.
🧪 Forms & quality
Kelp/seaweed-derived iodine varies widely in actual iodine content and can carry heavy metals such as arsenic; third-party testing statements are commonly recommended.
See the supplement glossary for what form names like "L-", chelated, or standardized extract mean.
📏 Dose & monitoring
NIH ODS sets an adult UL of 1,100 mcg per day (ages 19+) from food and supplements.
Evidence vs. burden: Moderate evidence relative to burden
Labs that may be worth discussing: Thyroid
Thyroid measures may be worth discussing with a healthcare professional before and during long-term iodine use.
These are discussion prompts, not required tests. A healthcare professional can advise what makes sense for you.
😐 Commonly reported side effects
- Both low and high intakes can affect thyroid function
- Digestive upset at high doses
Non-exhaustive and individual.
🔄 Cycling & breaks
No established cycling pattern.
📅 Daily use notes
Because both too little and too much iodine affect the thyroid, anyone with a thyroid condition or on thyroid medication should discuss iodine with a professional before supplementing.
📋 Source review status
Source-reviewed — last reviewed 2026-07-02
Placeholder — verify with NIH ODS iodine fact sheet and MedlinePlus before publishing; note that kelp and seaweed-derived iodine content is highly variable and such products can carry heavy-metal or contamination concerns.
Research backlog (queries to verify):
- iodine intake thyroid function too much too little
- kelp seaweed iodine content variability contamination
- iodine thyroid medication interaction caution
📚 References
- NIH ODS — Iodine (Health Professional Fact Sheet)NIH ODS — Verified UL, bidirectional thyroid effects, and interactions (antithyroid meds; potassium iodide with ACE inhibitors/potassium-sparing diuretics).
- NIH ODS — Iodine (Consumer Fact Sheet)NIH ODS — Full text reviewed 2026-07-03. Verified: adult UL 1,100 mcg; high iodine can cause goiter, thyroid inflammation, and thyroid cancer (same-direction as deficiency); interacts with antithyroid drugs (methimazole), and potassium iodide with ACE inhibitors / potassium-sparing diuretics can raise blood potassium; pregnancy needs are higher.
Verified against the source shown. See the research-status page for how review works.
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