Mineral

Selenium (Selenomethionine)

Also known as: L-selenomethionine, Organic selenium

Evidence

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.

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Daily target & upper limit

55 mcg / day · UL 400 mcg

Selenium (Selenomethionine) has an established daily reference intake. See best forms, label synonyms, upper-limit warnings, and top-scoring supplements:

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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.

Thorne

Selenium

Thorne

Thyroid Health Complex (formerly Thyrocsin)

Thorne

Advanced Nutrients

Thorne

Basic Nutrients 2/Day

See all products →

Evidence notes

Well-established for thyroid and antioxidant

Grade A: Multiple well-designed human trials support the main claims.

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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.