“GMP-certified” describes factory processes, not what is in the bottle. The claim does not name a certifier or public register that a shopper can check.

Magnesium Glycinate 400mg | 180 Capsules | Sleep
Checked against public sources on July 24, 2026 · LookCloser does not sell or recommend supplements.
Does the marketing hold up?
The barcode identity checks out · 850033272215. The barcode matches, so we are checking the right product rather than a look-alike.
“Couldn’t verify” means we looked and found no public proof — not a mark against the product. Most supplement claims cannot be independently verified by anyone, so grey is the normal state of this industry.
The checks, one by one
The public sources did not settle the marketing promises on this label.
◐Partly confirmed3
Published research exists for ingredients in this formula — see Related research below. Whether this product’s doses match those studies could not be confirmed.
A testing body is named on the listing, but we found no lot-specific certificate of analysis.
Ingredient research can support context, but it is not a trial of this exact product.
?Couldn’t verify independently1
“Made in USA” can describe only final bottling. Ingredient-sourcing records were not located for this product.
We looked and found no public proof. That does not count against the product.
What is worth knowing.
Headlines first. Open evidence only when you want the source trail.
The barcode identity checks out · 850033272215.
The barcode matches, so we are checking the right product rather than a look-alike.
Evidence and sources
UPCitemdb resolves 850033272215 to "Magnesium Glycinate - 180 x 400 mg capsules" (Double Wood Supplements) — consistent with this listing.
Locked evidence record →Open the full source-linked findingReviews grew steadily — about 1,230 between January 28, 2026 to July 12, 2026, with no sudden spike.
Gradual growth is more ordinary. A sudden burst deserves a closer look.
Evidence and sources
Written reviews grew from 3659 to 4835 across 2026-02-04 – 2026-07-12 with no single manufactured spike (largest 30-day gain ~286).
Locked evidence record →Open the full source-linked findingWhat remains open 2
- Panel amounts still need a clearer source image.
- No matched to this exact product public label filing is saved in this record.
These are evidence gaps, not strikes against the product.
Filed address
22 Lindsey Ave, Danville, PENNSYLVANIA 17821, UNITED STATES
USPTO identifies the public owner or applicant behind this brand wordmark. This does not by itself identify the product manufacturer or prove where the product was made. Open USPTO source ↗
Dose and research context
The label amount is shown beside the ranges used in the linked ingredient studies.
Price check for this exact product
Amazon
Exact UPC/GTIN match$0.09 per labeled serving
matching UPC/GTIN · checked Jul 25, 2026
View on Amazon ↗iHerb
Exact UPC/GTIN match$0.10 per labeled serving
matching UPC/GTIN · checked Jul 24, 2026
View on iHerb ↗Brand website
Official product-page candidate · UPC absentOfficial shopping lead; excluded from exact price comparisons.
Magnesium Glycinate Extra Strength · Double Pack. Confirm the package UPC/GTIN before buying.
Check brand website ↗Walmart
Not confirmedSearch results remain not linked to this exact product until this retailer publishes the matching UPC/GTIN.
Search Walmart ↗Same UPC/GTIN observed across 2 sellers. Amazon was lowest at $16.99; iHerb was highest at $17.95 — a $0.96 range at check time.
The brand-page price is shown as a shopping lead only. It is excluded from the exact-product price difference because the page does not publish this record's matching UPC/GTIN.
Reference prices only · no affiliate links · every compared seller must publish the matching UPC/GTIN.
Want the complete evidence trail?
The summary stops at product-specific facts. The full report preserves every source, calculation, limitation, and unresolved check for review or sharing.
Record built July 24, 2026. Sources: source listing observed at check time · USPTO Trademark Search · Keepa exact-listing history · NIH / published research · certification and regulator records where available. LookCloser publishes evidence and gaps; it does not advise for or against any supplement. Evidence-based corrections welcome.