howtosupplement
Deficiency/Hormonal

Selenium

Essential trace mineral that corrects low selenium status and may support thyroid health in adults with low intake.

Selenium

Selenium

58
score
B
evidence
Caution
risk

Proven Benefits

01Corrects selenium deficiency
02May lower TPO antibodies
03May improve sperm motility
04May improve viral clearance
05May improve thyroid wellbeing
06May reduce hair/nail changes

Chemical Forms

Recommended
  • L-selenomethionine
  • Selenium yeast
  • Sodium selenite
Avoid
  • Unstandardized Brazil nut powders (selenium content varies widely)
Expert Note

L-selenomethionine and selenium yeast are well-studied, well-absorbed forms that raise body selenium stores predictably. Sodium selenite also works, but inorganic forms are generally retained less. Unstandardized food-based powders can vary too much in selenium content to dose safely.

Protocol

Amount
100-200 mcg
Frequency
Once daily
When
With food is fine; consistency and total daily intake matter more than exact timing.

Condition-Based Dosing

Confirmed low plasma or serum selenium, or very low dietary intake
100-200 mcg daily for 8-12 weeks, then reassess total intake.
Thyroid antibody support under clinician guidance
200 mcg daily for 3-6 months, then recheck thyroid labs and TPO antibodies.
Adequate diet plus a multivitamin already containing selenium
No standalone selenium, or <=55 mcg/day from a multivitamin only.

Safety & Limits

Upper Safe Limit
400 mcg/day (IOM UL for adults)
Cycling
Safe for continuous use

Contraindications

High baseline selenium intake or frequent Brazil nut use — easier to exceed the UL and develop selenosis
Prediabetes or type 2 diabetes — long-term high-dose selenium may worsen glycemic risk in some studies
Pregnancy or breastfeeding — avoid high-dose use unless a clinician advises it
Chronic kidney disease — use only with clinician oversight because needs and handling can differ

Synergies

Iodine

Selenium-dependent deiodinases activate T4 to T3, and selenium antioxidant enzymes help protect the thyroid during iodine use.

Vitamin E

Both nutrients help limit oxidative damage, and adequate vitamin E supports the antioxidant network selenium-dependent enzymes work within.

Avoid Combining With

  • ✕Large vitamin C doses taken with sodium selenite (may reduce absorption — separate by 1 hour)
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