Types of Selenium (Thyroid): Forms & Bioavailability

SupplementScience.ai Editorial Team·Evidence-Based Supplement Research

Published Mar 11, 2026

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Forms Comparison

Form	Bioavailability	Best For
Selenomethionine	High (>90% absorbed)	General thyroid support — most studied form, incorporated into body proteins
Selenium Yeast	High	Whole-food form — contains multiple selenium species including selenomethionine
Sodium Selenite	Moderate (50-60%)	Budget option — inorganic form, less well-retained in tissue

Selenomethionine

Bioavailability: High (>90% absorbed). Best for: General thyroid support — most studied form, incorporated into body proteins.

Selenium Yeast

Bioavailability: High. Best for: Whole-food form — contains multiple selenium species including selenomethionine.

Sodium Selenite

Bioavailability: Moderate (50-60%). Best for: Budget option — inorganic form, less well-retained in tissue.

Full Selenium (Thyroid) Guide

References

Gärtner R, Gasnier BC, Dietrich JW, Krebs B, Angstwurm MW (2002). Selenium supplementation in patients with autoimmune thyroiditis decreases thyroid peroxidase antibodies concentrations. Journal of Clinical Endocrinology & Metabolism. DOI PubMed
Marcocci C, Kahaly GJ, Krassas GE, Bartalena L, Prummel M, Stahl M, Altea MA, Nardi M, Pitz S, Boboridis K, Sivelli P, von Arx G, Mourits MP, Baldeschi L, Bencivelli W, Wiersinga W (2011). Selenium and the course of mild Graves' orbitopathy. New England Journal of Medicine. DOI PubMed
Negro R, Greco G, Mangieri T, Pezzarossa A, Dazzi D, Hassan H (2007). The influence of selenium supplementation on postpartum thyroid status in pregnant women with thyroid peroxidase autoantibodies. Journal of Clinical Endocrinology & Metabolism. DOI PubMed