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Iodine
An essential trace mineral, and the raw material your thyroid uses to make its hormones. It carries five authorised EU health claims, one of them for normal thyroid function. We serve it in a single blood-test formula for the thyroid, at 150 µg, which is exactly the NRV. Our own file on it is still a minimal one, and its full review is pending.
WHAT WE ARE ALLOWED TO SAY
Five claims. All of them authorised.
These are the wordings on the EU register for iodine, and we do not paraphrase them into something that sounds stronger. All five carry the same condition: the product has to be at least a source of iodine under Regulation (EC) 1924/2006. Functional thyroid serves 150 µg, which is 100% of the NRV.These are the wordings on the EU register for iodine, and we do not paraphrase them. All five need the product to be at least a source of iodine. Functional thyroid serves 100% of the NRV.
None of the five is a claim about your TSH, about goitre or about any thyroid disease. Normal thyroid function is as far as the wording goes. The claim is what we are allowed to say; your blood test is the reason the formula that carries iodine goes on a plan.
WHY POTASSIUM IODIDE
The claims do not change. Knowing the exact dose does.
The five claims attach to iodine, not to a particular form, so the form is not a claim argument and we do not use it as one. Our regulatory file names two acceptable sources: potassium iodide or standardised seaweed. We use potassium iodide. Our files mark it as dissolving in water, stable in liquid and neutral in taste, and our notes record 92 to 100% of it as absorbed.
Kelp and kombu are natural sources of iodine, but our kombu file records anything from 1,500 to 8,000 µg of iodine in a single gram. With a spread like that you cannot know what a dose holds, so we do not use raw seaweed.
A seaweed extract standardised to a known amount of iodine. Our regulatory file accepts it alongside potassium iodide, and kombu is on our list of candidates in that form only. It is not what we use today.
A simple salt of iodine. It dissolves in water, stays stable in liquid and has a neutral taste, which suits a liquid system. Our notes record it at 92–100% absorbed.
High absorption is what our notes record, not an authorised claim, so you will not read it on a label. Our files also mark potassium iodide as sensitive to light. And there are open points we would rather write down: our notes put iodine at around 80 days in thyroid tissue, but we have not found a half-life in your blood yet, and the formula record does not yet name the form of iodine it carries.High absorption is not an authorised claim. Potassium iodide is sensitive to light, and we have no half-life for iodine in your blood on file yet.
WHERE IT APPEARS
One of the twenty-nine carries iodine.
Functional thyroid is a blood-test formula for a TSH drifting up with no sign of autoimmunity, and it is pending clinical validation. It runs 12 weeks, every morning before breakfast, and ends with a new test. If your TSH is back in range, it comes out and Energy & vitality, or simply your diet with iodised salt, takes over. Iodine is not in any CORE or BOOST formula today.
THE CEILING
600 µg a day, and your diet counts.
The EFSA upper limit for iodine is 600 µg a day for adults, four times the NRV. France's ANSES works to the same 600 µg, counting food and supplements together, and our files count iodised salt and the rest of your diet as part of that total. Germany's BfR suggests no more than 100 µg a day in a food supplement, the most conservative reference in the EU, and Functional thyroid, at 150 µg, is above it.The limit covers your total iodine, iodised salt and the rest of your diet included. Functional thyroid serves a quarter of it.
Functional thyroid runs 84 days at 150 µg every morning, then your TSH and free T4 are tested again. Our file sets no fixed pause and no yearly cap: at this dose iodine stays under its EFSA upper limit, which is what allows continuous use. How many cycles you get depends on your TSH, test by test.
Our kombu file asks for all iodine to be added up, with a total of no more than 600 µg a day: potassium iodide, seaweed and the iodised salt in your diet. That rule is written in a file; there is no engine rule for iodine yet, because only one formula carries it.
Contraindicated if you are hypersensitive to iodine. With autoimmune thyroid disease, Hashimoto's or Graves', talk to a healthcare professional before you start. Functional thyroid, the formula that carries it, is ruled out in pregnancy, with overt hyperthyroidism and with thyroid nodules still being investigated. Because of the other ingredients in it, it is also not given with liver disease or with vitamin K antagonist anticoagulants such as warfarin or acenocoumarol. It is meant for a thyroid with no sign of autoimmunity: if your TPO antibodies come back positive, you move to Autoimmune thyroid instead. Do not exceed the daily dose, or 600 µg of iodine a day in total. A food supplement is not a substitute for a varied and balanced diet. Keep it out of the reach of young children. Our file records none of the fourteen allergens that must be declared in the EU, and no known intolerance or dietary restriction.
WHAT IT REACTS WITH
No documented pairs yet. A few flags.
Iodine is one of the 140 ingredients in our library, so it has 139 possible partners. None of its pairs has been entered in our interaction tables yet, out of the 443 pairs on file, and it has no entry in our medication matrix. What follows comes from the files of the ingredients around it and from the formula that carries it.
Our selenium file rates iodine as a favourable partner: selenium is a cofactor of the enzymes that turn T4 into T3, and a lack of it compromises how your body uses iodine. That is why the two are formulated together in Functional thyroid. It is a note on mechanism, not a documented pair yet.
Our kombu file rates other iodine supplements, potassium iodide included, as a major pair, because iodine adds up and the total has to stay under 600 µg a day. Our ashwagandha file flags seaweed with iodine as adding to its effect on the thyroid, a moderate pair. Maca and broccoli sprout extract list iodine as offsetting a theoretical effect of their compounds on the thyroid at high doses, and our soy isoflavone file asks for care when iodine is low.
If you take levothyroxine, Functional thyroid is kept at least 4 hours away from it. Our kombu file also rates levothyroxine and antithyroid drugs such as methimazole and PTU as a major interaction for iodine from seaweed, because it can unsettle your TSH, and lists lithium and amiodarone, which brings its own iodine, as moderate. None of these is in our medication matrix for iodine yet. If you take any of them, ask your doctor before starting.
443 of the 9,730 possible pairs in our library are documented, which is 4.55%. The rest are not "safe", they are simply unchecked, and we would rather write that down than let the number look like a badge.443 of the 9,730 possible pairs in our library are documented, which is 4.55%. The rest are not safe, they are simply unchecked, and we would rather write that down than let the number look like a badge.
SOURCES
Everything on this page, with its reference.
Reviewed by VION nutrition team · last reviewed 16 September 2026Read the introduction to Potassium Iodide →
140 INGREDIENTS · 64 IN USE TODAY
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What it is, what we are allowed to say about it, which formulas carry it, what it reacts with and where each of those statements comes from. No proprietary blends, no hidden amounts.