What does the evidence show about Selenium's effects?

Read Off Label rates the evidence for Selenium as Strong and the benefit magnitude as med, producing an overall grade of B+ (7.2/10). Important for thyroid function (Hashimoto's).

What safety findings are reported for Selenium?

Selenium has a low-med risk profile in the database. Low-Med (narrow therapeutic window; selenosis at high doses) Legal status: OTC.

What doses or routes are reported for Selenium?

55-200 mcg/day; UL 400 mcg/day; selenomethionine is a commonly studied form This is context from studies, approved labeling, clinical practice, or documented use; it is not individualized guidance and does not establish safety.

Rankings / Essentials — Vitamins & Minerals

Selenium

Essentials · Mineral

Tier B+

Reviewed by Read Off Label · Last reviewed Jun 8, 2026 · How we grade

thyroidmineralantioxidantglutathioneotc

7.2 / 10

Tier B+

Ev 8 Bn 5 Sf 7

Bottom line

Read Off Label grades Selenium as B+ (7.2/10) based on strong evidence, med benefit magnitude, and a low-med-risk safety profile.

Important for thyroid function (Hashimoto's).

Studied, labeled, or reported-use context: 55-200 mcg/day; UL 400 mcg/day; selenomethionine is a commonly studied form — OTC; not individualized guidance.

What the evidence says

Important for thyroid function (Hashimoto's). SELECT trial found no prostate cancer benefit — even slight harm signal. 2 Brazil nuts/day provides RDA.

Mechanism

Selenoprotein cofactor (glutathione peroxidase, thioredoxin reductase); antioxidant; thyroid hormone deiodinase

Studied, labeled, or reported dose & route

55-200 mcg/day; UL 400 mcg/day; selenomethionine is a commonly studied form

This records doses and routes described in studies, approved labeling, clinical practice, or documented use. It is not individualized guidance and does not establish safety; context changes with indication, formulation, health history, monitoring, and other medicines.

Citations

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Common questions

What does the evidence show about Selenium's effects?: Read Off Label rates the evidence for Selenium as Strong and the benefit magnitude as med, producing an overall grade of B+ (7.2/10). Important for thyroid function (Hashimoto's).
What safety findings are reported for Selenium?: Selenium has a low-med risk profile in the database. Low-Med (narrow therapeutic window; selenosis at high doses) Legal status: OTC.
What doses or routes are reported for Selenium?: 55-200 mcg/day; UL 400 mcg/day; selenomethionine is a commonly studied form This is context from studies, approved labeling, clinical practice, or documented use; it is not individualized guidance and does not establish safety.
How does Selenium work?: Selenoprotein cofactor (glutathione peroxidase, thioredoxin reductase); antioxidant; thyroid hormone deiodinase

This is an independent synthesis of published research by a non-clinician. Scores are opinions supported by citations, not prescriptions. See the full disclaimer and methodology for how this score was produced and what it does and doesn't mean.