Supplement Label Index

Copper Gluconate vs. Cupric Oxide

Among 3,989 on-market copper products with an identifiable primary form, 35.2% use Copper Gluconate (1,405 products) and 12% use Cupric Oxide (478).

Copper GluconateCupric Oxide
Quality tierTier 2Tier 3
Copper by weight14.0%79.9%
Share of market35.2%12%
On-market products1,405478
Median declared dose1,000 elemental mcg
middle half: 500–2,000
2,000 elemental mcg
middle half: 1,600–2,000
Most common brandsDC, Wonder Laboratories, Biotics Research CorporationGNC Women's Ultra Mega, GNC Mega Men, Vitamin World

Doses are declared per serving in elemental mcg. “By weight” is the share of the ingredient that is the nutrient itself (e.g. elemental magnesium in a magnesium salt).

Why Copper Gluconate is tier 2

Water-soluble, generally regarded as acceptably absorbed, but no dedicated head-to-head human bioavailability RCT was located.

Source: uncertain -- needs review

Why Cupric Oxide is tier 3

Provides essentially no bioavailable copper relative to CuSO4 per chick/rat data.

Source: Baker DH. 1999, J Nutr 129:2278-9, PMID 10573563

Tiers summarize published comparative bioavailability or outcome evidence for each form (see methodology). This page describes the market; it is not a recommendation to take either form. Talk to a clinician about what's right for you.

Other copper comparisons