Selenium
Selenium in tablets, capsules and drops, from L-selenomethionine and selenium yeast to the selenite and selenate salts. We explain how the forms differ, which strength suits a UK diet and how to stay under the upper limit.Read more →
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Selenium forms, strengths and how much you actually need
Selenium is a trace mineral. The body needs it in micrograms, not milligrams, and cannot make it. It is built into roughly 25 proteins, known as selenoproteins, which the body uses for antioxidant defence, thyroid hormone activity and immune function.
How much you get depends on where your food grew. Selenium comes out of the soil, and soils in the UK and much of Europe hold less of it than the North American wheat belt. Average intakes here sit below the UK reference amount, which is one reason selenium is a familiar item on British supplement shelves. You will find it alongside the rest of our minerals.
The forms differ in how the body stores them
Nearly every selenium product uses one of four raw materials, and a good label names it.
- L-selenomethionine: selenium bound to the amino acid methionine, the same shape it takes in food. Well absorbed, and stored in body protein, so levels rise gradually.
- Selenium yeast: yeast grown on a selenium-rich medium, mostly selenomethionine. Not an option if you avoid yeast.
- Sodium selenite and sodium selenate: mineral salts. Also well absorbed, but not stored in protein, so they work more like a daily top-up.
Strength matters more here than with most minerals. The UK reference amount is 75 micrograms a day for men and 60 for women, while a large share of products provide 200 micrograms. That is normal and widely sold, but the distance between enough and too much is shorter for selenium than for something like vitamin C. Six Brazil nuts can add several hundred micrograms on their own, so your total intake, not the single tablet, is the number that counts.
How we choose selenium
We lead with L-selenomethionine and selenium yeast, because both are the food-bound forms and both are well absorbed. Selenite and selenate we mostly keep inside multivitamins, where the dose stays modest. On strength we deliberately carry lower options next to the familiar 200 microgram tablets, so you can match the supplement to your diet instead of defaulting to the biggest number. Combinations have to earn their place: we pass on formulas where a token few micrograms of selenium sit at the end of a long ingredient list. Every product passes our compliance team, and independent labs spot-check batches. Read how we select brands and products.
Who it suits
Selenium is worth considering if you eat little fish, meat or eggs, or if your diet is mainly plant based and grown on European soil. It also suits people who would rather not rely on Brazil nuts, since the selenium content of one nut varies enormously with its origin. Low intakes of selenium and iodine sources often turn up in the same diets, so it is worth checking both.
Be realistic about the timeline. Blood selenium shifts over weeks, not days, so judge a supplement after two to three months of consistent use rather than after a fortnight. More is not better either: if your intake is already adequate, extra selenium adds nothing you will notice, and very high intakes are linked to hair loss. If you also take a multivitamin, a hair and nail product or one of our antioxidant formulas, add up the selenium on every label before you pick a strength.
Frequently asked questions
Selenium is an essential trace mineral that the body builds into selenoproteins. Under EU approved wording, selenium contributes to the normal function of the immune system, to normal thyroid function, to the protection of cells from oxidative stress, to the maintenance of normal hair and normal nails, and to normal spermatogenesis.
Those are the only claims permitted, and they describe normal function being maintained. They do not mean a supplement treats a condition or improves anything beyond a normal level.
Not everyone. Selenium enters the food chain through soil, and UK soil is relatively low in it. Since British flour shifted away from selenium-rich North American wheat, average intakes here have fallen below the UK reference amount.
If you regularly eat fish, shellfish, meat and eggs, you are likely to be fine. The gap tends to appear in mainly plant-based diets built on European produce, and in diets that are low in animal protein overall.
For daily use, the food-bound forms are the usual starting point. If you avoid yeast, L-selenomethionine is the straightforward choice.
| Form | What it is | Suits |
|---|---|---|
| L-selenomethionine | Amino acid bound | Daily use, yeast-free |
| Selenium yeast | Yeast grown on selenium | Food-form preference |
| Sodium selenite | Mineral salt | Multivitamin blends |
| Sodium selenate | Mineral salt | Liquids and drops |
The salts are absorbed well too, but they are not stored in body protein, so they behave as a daily top-up rather than building a reserve.
The UK reference nutrient intake is modest, and the safety ceilings sit well above it. Two figures circulate because two bodies set them for different purposes.
| Group | Per day | Set by |
|---|---|---|
| Men 19 to 64 | 75 µg | NHS |
| Women 19 to 64 | 60 µg | NHS |
| Adults, upper intake level | 255 µg | EFSA |
| Adults, from supplements | 350 µg | NHS |
You can, but the dose is unpredictable. A single Brazil nut supplies roughly 68 to 91 micrograms of selenium according to US health authority figures, and the exact amount depends on the soil the tree grew in. Two nuts might cover your day, or push you far past it.
A tablet gives you a known number on the label. That is the practical argument for supplementing rather than counting nuts, especially if you are already close to the upper limit.
Take it with a meal. Selenium is absorbed well either way, but food reduces the chance of mild stomach upset, and tying it to breakfast makes it easier to remember.
Do not expect a quick signal. Blood selenium responds over weeks, and the protein-bound forms build up gradually, so give it two to three months of consistent daily use before judging it. If you are topping up a low intake, the value is in maintaining normal levels, not in a noticeable effect on day three.
Yes, but check the totals. Multivitamins commonly contain 55 micrograms of selenium, and hair, skin and nail formulas often add more. Stack a 200 microgram tablet on top and you can approach the ceiling without meaning to.
Add up every label first. If your multivitamin already covers the reference amount, a lower strength selenium product usually makes more sense than a second high dose. The same logic applies to combined hair and nail supplements.
EFSA set its adult upper intake level of 255 micrograms a day to cover pregnant and breastfeeding women as well. That is a safety ceiling, not a target, and NHS guidance is to speak to your midwife or GP before starting any supplement in pregnancy.
If you have a thyroid condition or take thyroid medication, discuss it with your doctor first. Selenium contributes to normal thyroid function, but that is not the same as supporting a diagnosed condition, and your total intake matters more than the form you pick.
