Iodine
Iodine supplements in tablets, capsules and liquid drops, from potassium iodide to seaweed sources. We explain how the forms differ, why an exact dose per serving matters and who genuinely needs to top up.Read more →
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Iodine forms, doses and who needs a supplement
What iodine does in the body
Iodine is a trace mineral your body cannot make itself. The thyroid, a small gland in the neck, uses iodine to build the hormones T3 and T4. Iodine contributes to the normal production of thyroid hormones and to normal thyroid function. It also contributes to normal cognitive function, normal functioning of the nervous system, normal energy-yielding metabolism and the maintenance of normal skin.
In the UK, cows' milk, dairy and white fish supply most of the iodine people get. Iodine in plant foods follows the soil, so levels vary from field to field. Swap dairy for a plant drink that is not fortified with iodine and your intake can fall without you noticing. Iodine is one of the trace elements in our Minerals range, needed in micrograms rather than milligrams.
The forms differ mainly in dosing accuracy
Most tablets and capsules use potassium iodide or potassium iodate. Both deliver iodine well. Iodate is a little more stable on the shelf, which is why some brands prefer it. The useful part is that the amount is fixed per tablet, usually 150 mcg, sometimes 100 mcg or 225 mcg, so you know what you take each day.
Kelp, sea moss and other seaweed products work differently. Their iodine content depends on the harvest and the species, so one capsule can supply several hundred micrograms and the next batch more again. Liquid drops sit in between: they let you dose in small steps, handy if you want less than a full tablet, but you have to count drops carefully.
How we choose the iodine we stock
We look at three things: the form, the amount per serving and the combinations that make sense. For iodine we prefer forms with a fixed, declared dose, potassium iodide or potassium iodate, because 150 mcg on the label should mean 150 mcg in the capsule. We do stock seaweed products, and we say plainly that their content varies more. We do not present high-strength iodine solutions as a daily supplement, because those doses sit far above what a normal diet needs. Every product passes our compliance team, we test ourselves, and independent labs spot-check batches. Read how we select our brands.
Who a supplement genuinely suits
Topping up makes most sense when your diet is low in iodine. That usually means:
- no fish and no dairy, for example on a plant-based diet
- no iodised salt, which is uncommon in British kitchens
- plant drinks that are not fortified with iodine
If that describes you, a modest fixed dose is the practical route, and you will find more options among our products for a vegan diet. If you eat fish, eggs or dairy most days, you are probably already covered.
Selenium is often bought alongside iodine. It carries its own approved claim for normal thyroid function, which is a separate claim, not evidence that the two work better as a pair. If that interests you, browse the selenium range and decide per nutrient.
Be honest with yourself about what to expect. Iodine is not a supplement you feel working from one day to the next. Its value is quiet: it fills a gap in the diet so a normal process can keep running normally. More is also not better here. The NHS advises that 0.5 mg or less a day from supplements is unlikely to cause harm, and standard products stay well below that.
Frequently asked questions
Iodine is an essential trace mineral. The body cannot produce it, so it has to come from food or a supplement. The thyroid gland stores most of the iodine in your body and uses it to make the hormones T3 and T4. Iodine contributes to the normal production of thyroid hormones and to normal thyroid function, and also to normal cognitive function, normal nervous system function, normal energy-yielding metabolism and the maintenance of normal skin.
UK guidance gives a daily figure for adults plus a ceiling for supplements. The table below shows the official reference values, not personal advice.
| Reference | Amount per day |
|---|---|
| Adults, daily need | 140 mcg |
| From supplements, unlikely to cause harm | 0.5 mg (500 mcg) |
| Tolerable upper level, total intake | 600 mcg |
A typical supplement supplies 150 mcg, which is the EU nutrient reference value used on labels.
Source: NHS and Committee on ToxicityThe main practical difference is how exactly you can dose.
| Form | Dose accuracy | Suits |
|---|---|---|
| Potassium iodide | Fixed per tablet | Daily top-up |
| Potassium iodate | Fixed, stable | Long shelf life |
| Kelp or sea moss | Varies per batch | Whole-food preference |
| Liquid drops | Depends on drop counting | Small, flexible doses |
For most people a fixed 150 mcg tablet or capsule is the simplest choice, because you always know the amount you took.
They are real sources, but not precise ones. Seaweed takes up iodine from seawater, and the amount depends on the species, the harvest and the season. That is why one kelp capsule can deliver a few hundred micrograms while another product delivers far more. If you like a whole-food source, look for a label that states a tested iodine amount per capsule. If you want to control your intake to the microgram, a standardised potassium iodide or iodate product is the clearer option.
Take it once a day, with a meal, at a time you will remember. Iodine does not depend on food for absorption, but a fixed routine prevents doubling up or skipping. Splitting a 150 mcg tablet is unnecessary; the daily amount is already small. If you take a general multivitamin, check the label first, because many already contain 150 mcg of iodine and you do not need both.
Probably not, and that is normal. Iodine works in the background: it supplies the raw material for thyroid hormones rather than producing a sensation you can feel. If your diet was already adequate, adding more changes nothing you would notice. If your intake was genuinely low, any change shows up over weeks in blood or urine values measured by a healthcare professional, not in how you feel by Friday. Judge iodine on whether it closes a real gap in your diet.
Iodine needs attention in this period, and it is also a moment for individual advice. UK reference values do not add an extra amount for pregnancy or breastfeeding, and the NHS advises speaking to a healthcare professional before starting any iodine supplement. Many pregnancy multivitamins already contain around 150 mcg, so check the label before adding a separate product. High-strength kelp and concentrated iodine solutions are not suitable here, because the dose is unpredictable or far too high.
This is the one situation where you should not decide alone. Both too little and too much iodine can affect how the thyroid works, and the NHS notes that high doses taken over long periods could change thyroid function. If you have an overactive or underactive thyroid, an autoimmune thyroid condition, or you take thyroid medication, lithium or amiodarone, ask your GP before starting. They can judge your intake against your treatment. A supplement is not a substitute for that conversation.
