Forms of selenium
| Form | What it is |
|---|---|
| L-selenomethionine | Selenium built into the amino acid methionine. According to NIH ODS, this is also the main form of selenium in food. |
| Selenium yeast (e.g. SelenoExcell) | Yeast grown on a selenium-rich medium. The label states the selenium content in µg. |
| Sodium selenite, selenate | Inorganic forms, used mostly in multivitamins. |
Reading the dose
Selenium is dosed in micrograms (µg), a thousandth of a milligram. The EU NRV is 55 µg.
| Selenium per daily dose | % of NRV (55 µg) |
|---|---|
| 55 µg | 100% |
| 100 µg | 182% |
| 200 µg | 364% |
In 2023 EFSA set a tolerable upper intake level of 255 µg a day for adults, from all sources together. A 200 µg product stays below it, but many multivitamins and hair formulas also contain selenium. If you take one of them alongside a selenium product, add the amounts together and stay within the daily doses on the labels.
Selenium products compared
| Product | Form | Daily dose | Selenium | Pack lasts |
|---|---|---|---|---|
| NOW Foods Selenium 100 µg, 100 tablets | L-selenomethionine | 1 or 2 tablets with a meal | 100 or 200 µg | 50 to 100 days |
| NOW Foods Selenium 200 µg, 90 capsules | L-selenomethionine, vegetable capsule | 1 capsule with a meal | 200 µg | 90 days |
| Swanson Selenium 100 µg, 200 or 300 capsules | SeLECT L-selenomethionine | 1 capsule | 100 µg | 200 or 300 days |
| Swanson SelenoExcell 200 µg, 60 capsules | selenium yeast, gelatin capsule | 1 capsule | 200 µg | 60 days |
The tablet count says little until you know the daily dose. The price per day on each product card already accounts for it.
Selenium and zinc
Selenium and zinc are often bought together, and some formulas put them in one tablet. OstroVit Biotin Plus, for example, has 100 µg of selenium (182% NRV) and 15 mg of zinc (150% NRV) alongside biotin and folic acid. A combined label lists each mineral on its own line with its own % NRV, so check both lines against any other product you take. Single zinc products are in our zinc category.
Selenium benefits under EU-authorised claims
Regulation (EU) No 432/2012 permits these statements for products that provide at least 15% of the NRV per daily dose. Every product in this category meets that condition:
- Selenium contributes to the normal thyroid function.
- Selenium contributes to the normal function of the immune system.
- Selenium contributes to the protection of cells from oxidative stress.
- Selenium contributes to the maintenance of normal hair.
- Selenium contributes to the maintenance of normal nails.
- Selenium contributes to normal spermatogenesis.
Selenium in food
NIH ODS lists seafood and organ meats as the richest food sources, with meat, grains and dairy also contributing. How much selenium a plant food holds depends on the soil it grew in, so the same food can differ between regions. A supplement gives you a fixed amount that is printed on the label.
Questions
100 µg or 200 µg?
Both are above the 55 µg NRV and below the 255 µg EFSA limit on their own. If you also take a multivitamin with selenium, 100 µg leaves more room.
How do I take selenium?
Follow the daily dose on the label: one or two tablets or capsules a day in this category. NOW Foods labels say to take them with a meal. Swanson labels give no set time.
Which form of selenium is best?
L-selenomethionine and selenium yeast are both organic forms, and all products here state the selenium content in µg. Choose by dose, capsule type and price per day.
Is selenium yeast vegan?
Yeast is not an animal product, but the Swanson SelenoExcell capsule shell is gelatin. NOW Foods 200 µg uses a vegetable capsule. Check the ingredient list of the product.
Can I take selenium and zinc at the same time?
Combined products are designed that way. If you use two separate products, follow each label and add up the amounts from everything you take.
Sources
- Regulation (EU) No 1169/2011, Annex XIII (reference intakes)
- Regulation (EU) No 432/2012 (permitted health claims)
- NIH Office of Dietary Supplements: Selenium fact sheet
- EFSA (2023): Scientific opinion on the tolerable upper intake level for selenium
Content reviewed by Inese Kalniņa, dietitian.
2026-07-23
