Selenium

Of 7,788 on-market selenium products in the January 2026 DSLD dump, the median declared dose is 55 elemental mcg, and 36.6% list unspecified/undisclosed form as the primary form.

7,788

on-market products

55 elemental mcg

median dose

46.6%

below RDA

1.1%

above UL

Form share

Of 7,404 products with an identifiable primary form, here is the share held by each form of Selenium on the market today.

Form	Quality tier	n	Share
unspecified/undisclosed form	Unrated	2,711	36.6%
L-Selenomethionine	Tier 1	2,697	36.4%
Selenium Amino Acid Chelate	Unrated	811	11.0%
Sodium Selenate	Tier 2	657	8.9%
Sodium Selenite	Tier 2	528	7.1%

Form share over time

Entry-year breakdown of the top forms, 2012–2025.

Dose distribution

Deciles of declared dose per serving (elemental mcg), among 7,245 products with a disclosed amount, against the RDA of 55 and UL of 400.

13.9% of products fall below the fairy-dust threshold (20 mcg, 20% of the studied low dose).
1.3% of products don't disclose an amount because Selenium is declared inside a proprietary blend.

By dosage form

By target group

Top brands

Brand	Products
Douglas Laboratories	272
Centrum	122
MegaFood	99
Source Naturals	97
New Chapter	95
Bluebonnet	95
Nature's Way	92
Wonder Laboratories	92
DC	87
Life Extension	86
GNC Mega Men	83
Pure Encapsulations	83
The Vitamin Shoppe	78
NOW	76
Metagenics	71
Carlson	69
XYMOGEN	68
Airborne	66
Garden of Life MyKind Organics	65
GNC Women's Ultra Mega	63
Bayer One A Day	62
Solgar	59
Vitamin World	58
Higher Nature	57
Puritan's Pride	53

Forms explained

unspecified/undisclosed form Unrated

Label discloses only "Selenium" with no compound specified.

L-Selenomethionine Tier 1

Elemental fraction: 40.3% (C5H11NO2Se, single defined molecule, no hydration ambiguity)

More complete absorption and greater tissue retention than selenite in comparative reviews; the form used in the two largest human RCTs (NPC, SELECT).

Source: Clark LC et al. 1996, JAMA 276(24):1957-1963; Lippman SM et al. 2009, JAMA 301(1):39-51

Selenium Amino Acid Chelate Unrated

Terminology inconsistent across manufacturers; needs manual review to determine actual composition.

Source: uncertain -- needs review

Sodium Selenate Tier 2

Elemental fraction: 21.4% (Na2SeO4 x 10H2O, decahydrate (described as the common supplement ingredient form vs 0.418 anhydrous -- spot-check against labels))

Inorganic selenate is well absorbed but, like selenite, less well retained in tissue than organic selenomethionine per general bioavailability literature.

Source: uncertain -- needs review for a direct comparative citation

Sodium Selenite Tier 2

Elemental fraction: 45.7% (Na2SeO3, anhydrous (standard dietary-supplement/premix form; a pentahydrate at 0.300 also exists -- check specific labels))

Well absorbed (~80%) but less well retained than organic selenomethionine per comparative bioavailability reviews.

Source: Fairweather-Tait SJ et al., selenium bioavailability review, Am J Clin Nutr -- specific comparative % vs selenate not independently re-verified

Reference values

RDA (adult): 55 elemental mcg
Tolerable Upper Intake Level (adult): 400 elemental mcg
Studied clinical dose range: 100–200 mcg
Lippman SM et al. 2009 (SELECT trial), JAMA 301(1):39-51 -- 200mcg/day L-selenomethionine did not reduce prostate cancer incidence over 7-12yr in 35,533 men (the vitamin E arm significantly increased risk). Corroborated by Clark LC et al. 1996 (NPC trial), JAMA 276(24):1957-1963, also 200mcg/day. Low end reflects smaller deficiency-correction/biomarker studies not independently pinned to one citation.
Note: unit_basis is elemental mcg, not mg, unlike most other minerals in this list.