Mineral
Selenium (Selenomethionine)
Also known as: L-selenomethionine, Organic selenium
Highly bioavailable organic selenium for thyroid and antioxidant function. Narrow optimal range requires careful dosing.
Last reviewed June 2026 · Evidence graded from peer-reviewed research, not editorial opinion. Educational only — not medical advice.
Every Selenium (Selenomethionine) product we have scored
| # | Product | Score | Per serving |
|---|---|---|---|
| 1 | Thorne Selenium | 96 A | $0.23 |
| 2 | Pure Encapsulations Selenium (citrate) | 94 A | $0.22 |
| 3 | Pure Encapsulations Selenium (selenomethionine) | 94 A | $0.24 |
| 4 | Nutricost Selenium Capsules | 94 A | $0.06 |
| 5 | Life Extension Se-Methyl L-Selenocysteine | 94 A | $0.09 |
| 6 | Natural Factors SelenoExcell Selenium | 92 A | $0.15 |
| 7 | Life Extension Super Selenium Complex & Vitamin E | 91 A | $0.10 |
| 8 | Thorne Thyroid Health Complex | 90 A | $0.33 |
| 9 | NOW Foods NAC | 89 A | $0.12 |
| 10 | MegaFood Skin, Nails & Hair 2 | 89 A | $0.87 |
| 11 | Thorne Advanced Nutrients | 88 A | $2.40 |
| 12 | Thorne Basic Nutrients 2/Day | 88 A | $0.60 |
Scored on dose accuracy, form, label transparency and third-party testing. Per-serving cost is list price divided by servings per container. No brand pays to be listed or ranked.
Common questions
How much Selenium (Selenomethionine) should I take?
The typical range is 100-200 mcg daily. Don't exceed 400 mcg
When should I take Selenium (Selenomethionine)?
Any. Optional.
Which form of Selenium (Selenomethionine) is best?
Selenomethionine — Well-absorbed. Other forms in the catalog: Selenium yeast.
Is Selenium (Selenomethionine) safe?
Commonly reported: Garlic breath at high doses. Serious warnings: Toxicity >400 mcg, Selenosis. Safe at normal doses
Which Selenium (Selenomethionine) supplement scores highest?
Thorne Selenium, at 96/100. Scored on dose accuracy, form, label transparency and third-party testing — no brand pays to be listed or ranked.
Daily target & upper limit
55 mcg / day · UL 400 mcgSelenium (Selenomethionine) has an established daily reference intake. See best forms, label synonyms, upper-limit warnings, and top-scoring supplements:
Selenium (Selenomethionine) dosage reference →Primary uses
- Thyroid support
- Glutathione system
- Immune function
How it works
- Incorporated into selenoproteins
- Essential for T4 to T3 conversion
- Supports glutathione peroxidase
Dosage
- Typical range
- 100-200 mcg daily
- Timing
- Any
- With food
- Optional
- Duration
- Don't exceed 400 mcg
- Special populations
- Thyroid patients
Forms
- Selenomethionine
- Selenium yeast
Safety
Common side effects
- Garlic breath at high doses
Contraindications
- High selenium status
Products containing Selenium (Selenomethionine)
Top-scoring supplements in our catalog that list Selenium (Selenomethionine) on the label. Each product is graded on Formulate's ingredient-level rubric — dose accuracy, form, transparency, and third-party testing.
Evidence notes
Well-established for thyroid and antioxidant
Grade A: Multiple well-designed human trials support the main claims.
Related in Mineral
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Medical disclaimer. This page is educational and does not replace advice from a qualified healthcare provider. Individual needs and risks vary — consult a professional before starting, stopping, or combining supplements, especially if you are pregnant or nursing, taking medication, or managing a health condition.