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Dosage guide

Selenium dosage guide: how much to take in 2026

Selenium works only at the right dose in the right form. This guide covers the effective range, timing, best forms, and interactions to know.

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US RDA

55 mcg daily

Effective dose

100 to 200 mcg daily for thyroid support

Upper limit

400 mcg daily

Timing

Any time

With food

Optional

Bioavailability

Selenomethionine > sodium selenite > selenite

Best forms to buy

Selenomethionine

Best absorbed, most researched

Brazil nuts (2 to 3 daily)

Food-based source

Sodium selenite

Cheaper, less bioavailable

Signs of deficiency

  • · Thyroid dysfunction
  • · Muscle weakness
  • · Poor immunity
  • · Hair loss

Drug interactions

  • · May reduce effects of some cholesterol medications

Toxicity

Hair and nail loss, garlic breath, GI issues, nervous system effects at doses above 400 mcg for extended periods.

FAQ

Common questions

How much Selenium should I take?

100 to 200 mcg daily for thyroid support

When should I take Selenium?

Any time

Can I take too much Selenium?

Hair and nail loss, garlic breath, GI issues, nervous system effects at doses above 400 mcg for extended periods.

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Sources

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This article is for informational purposes only and does not constitute medical advice. Consult a licensed healthcare provider before starting new treatments, supplements, or procedures. Links to products may be affiliate links. Smart Milky may earn a commission at no additional cost to you.