Selenium
Selenium is built into about 25 selenoproteins, including antioxidant enzymes and enzymes that activate thyroid hormone.
Full ranking Dose tool Products (3,209)
Key facts
Sources: https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/ · FDA DV 55 mcg (https://www.fda.gov/food/nutrition-facts-label/daily-value-nutrition-and-supplement-facts-labels); pre-2016 DV [70] (https://www.federalregister.gov/documents/2016/05/27/2016-11867/food-labeling-revision-of-the-nutrition-and-supplement-facts-labels); adult UL 400 mcg
How it works: What does selenium do in the body?
- Absorbed selenium is used to make about 25 selenoproteins.
- Some of them, such as glutathione peroxidases, take part in antioxidant defence.
- Iodothyronine deiodinases are selenoproteins involved in thyroid hormone metabolism.
Schematic only; positions and scale are not anatomical.
Sources: NIH ODS: Selenium Fact Sheet for Health Professionals
Daily dose across products (mcg/day)
Label data from official national databases and brand websites, as declared; not lab-verified.
Common forms
| Form | Products | Median | P5–P95 | Elemental fraction |
|---|---|---|---|---|
| Selenium selenomethionine | 1271 | 70 mcg | 10.5 – 200 | 40.3% [source] |
| Selenium selenite | 433 | 50 mcg | 3.5 – 250 | — |
| Selenium selenate | 172 | 50 mcg | 14 – 2,000 | — |
| Selenium yeast | 121 | 100 mcg | 12.5 – 200 | — |
Common questions
What is the Daily Value for Selenium?
The US FDA Daily Value for adults and children aged 4 and over is 55 mcg. It is a labelling reference, not a personal recommendation. [source]
Is there an upper limit for Selenium?
The adult Tolerable Upper Intake Level (UL) is 400 mcg per day. Going above it long term raises the risk of adverse effects. See the linked source. [source]
How much Selenium do products usually contain per day?
As of 2026-11-01, 3,209 products list a comparable daily dose (3,234 dose records; one product can have several). The median is 55 mcg per day, and 90% of records fall between 8 and 200 mcg. Figures come from labels and are not lab-tested. [source]
What does selenium do in the body?
Selenium is built into about 25 selenoproteins, including antioxidant enzymes and enzymes that activate thyroid hormone. Adult UL: 400 mcg per day. Long-term excess can cause selenium toxicity such as hair loss and brittle nails. [source]
What are the side effects of Selenium?
Too much selenium over time can cause garlic breath, a metallic taste, hair loss, brittle or lost nails, skin rash, nausea, diarrhea, extreme tiredness, irritability and nervous system problems. (Source: NIH ODS) [source]
What happens if you take too much Selenium?
The adult UL is 400 mcg a day from all sources; EFSA set 255 mcg in 2023. One Brazil nut has 68–91 mcg, so eating many can exceed the limit. Very high amounts can cause breathing difficulty, tremors, kidney or heart failure and, rarely, death. (Source: NIH ODS) [source]
Is Selenium safe during pregnancy and breastfeeding?
The recommended amount is 60 mcg a day in pregnancy and 70 mcg while breastfeeding; the UL is still 400 mcg. (Source: NIH ODS) [source]
Does Selenium interact with medications or other supplements?
The chemotherapy drug cisplatin can lower selenium levels, though the effect on the body is unclear. (Source: NIH ODS) [source]
Top ranked
| Rank | Brand | Product | Per day | Score |
|---|---|---|---|---|
| 1 | Swanson | SelenoExcell Selenium 200 mcg | 200 mcg | 100.0 |
| 2 | Swanson | Selenium 100 mcg | 200 mcg | 97.8 |
| 2 | GNC | Selenium 200 | 200 mcg | 97.8 |
| 2 | Nature's Bounty | Selenium 200 mcg | 200 mcg | 97.8 |
| 2 | CVS Pharmacy | Selenium 200 mcg | 200 mcg | 97.8 |