“CERTIFIED”
Evidence →“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.
Exact product checked · GTIN 00866812000122Double Wood Supplements · checked Jul 25, 2026 · on sale since Oct 10, 2016🇺🇸 USPTO wordmark owner · Double Wood LLC · PENNSYLVANIA, USAPackage says manufactured for: Double Wood LLC · 3510 SCOTTS LN STE 219
PHILADELPHIA, PA 19129-1573
United States
Quick read · Double Wood Supplements
Double Wood Supplements Magnesium L-Threonate (Magtein)…
Checked against public sources between July 25 and September 2, 2026 · LookCloser does not sell or recommend supplements.
120capsules · 30 servings
Does the marketing hold up?
Every ingredient shows its amount · 2 ingredients listed. Every ingredient shows its real amount — nothing is hidden in a proprietary blend.
Is the dose real?Panel read — dose not verified2 ingredients listed; no advertised amount we could confirm against them
What a serving costs$1.00per serving, at the checked price
Is it tested?NSF seal printed on the labelwe read it off the package photo; not confirmed in NSF’s registry
Who’s behind it?🇺🇸Double Wood LLClimited liability company · PENNSYLVANIA, USA
Is it the real thing?✓Barcode matches outside records
Trouble on record?Recall check not run yeta gap in our records, not a finding about the product
“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.
3◖ partly confirmed1△ support not found1? couldn’t verifyno contradictions · no recalls
The label itself
What the Supplement Facts panel says
| Magnesium L-Threonate (Magtein)® | 2000 mg |
|---|---|
| Providing elemental magnesium | 144 mg |
Printed on the package: GMP CERTIFIED · NSF · Third-Party Tested · Manufactured in the USA · From Globally Sourced Materials · CONTENTS CERTIFIED
We read 2 lines from the package photograph. It is our transcript of the label, not the manufacturer’s panel, and it may be incomplete.
Marketing claims, checked
The checks, one by one
1 promise needs a closer look.
◐Partly confirmed3
“Magnesium L Threonate, Magtein - NSF Certified - Sleep and Cognitive Support – High Absorption – Most Bioavailable Form of Magnesium – 2,000 mg – 120”
Evidence →Published research exists for ingredients in this formula. Whether this product’s doses match those studies could not be confirmed.
“Tested”
Evidence →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.
△Claimed without support found1
“FORM OF MAGNESIUM ABLE TO SUPPORT MAGNESIUM LEVELS IN THE BRAIN: Magtein Magnesium L-Threonate is a unique magnesium breakthrough supplement and…”
Evidence →We found no named, citable study of this product or formula. The claim may rest on ingredient research rather than a trial of this product.
?Couldn’t verify independently1
“in the”
Evidence →“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.
Quick read · 2 useful findings
What is worth knowing.
Headlines first. Open evidence only when you want the source trail.
CheckedIs the label honest?
Every ingredient shows its amount · 2 ingredients listed.
Every ingredient shows its real amount — nothing is hidden in a proprietary blend.
Evidence and sources
The panel gives a per-ingredient amount rather than hiding quantities inside a proprietary blend, so each one can be compared to published research.
Locked evidence record →Open the full source-linked findingCheckedWho is behind it?
The barcode identity checks out · 866812000122.
The barcode matches, so we are checking the right product rather than a look-alike.
Evidence and sources
The brand's store lists this exact barcode as “Magnesium L-Threonate (Magtein) Supplement” (variant: One Bottle) — identity confirmed across retailer listings.
Locked evidence record →Open the full source-linked findingWhat remains open 1
- We have not found a public label filing for this exact product.
These are evidence gaps, not strikes against the product.
Who owns the brand wordmark?
🇺🇸
Double Wood LLCLimited Liability Company · exact supplement-class mark for DOUBLE WOOD SUPPLEMENTS
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 ↗
Research behind the findings
Dose and research context
We could not match an amount on this product to a studied range for the same ingredient, so these links are ingredient background rather than a measurement of this product.
Background reading
What the research says about these amounts
Not a score. Studies disagree with each other and change over time, so this sits beside the evidence rather than counting toward it — it is here so you can read the sources yourself.
The panel lists 2 g of magnesium per serving. Studies we found used 200 mg–420 mg a day, so this sits above that range.
0studied 200 mg–420 mg
Study ranges differ between trials and change as research changes. This is background reading, not a pass, a failure, or a recommendation.
Where it sells
Price check for this exact product
Amazon
Exact UPC/GTIN match$29.95
$1.00 per labeled serving
matching UPC/GTIN · checked Aug 29, 2026
View on Amazon ↗iHerb
Exact UPC/GTIN match$29.95
$1.00 per labeled serving
matching UPC/GTIN · checked Jul 28, 2026
View on iHerb ↗Brand website
Exact UPC/GTIN match$30.95
$1.03 per labeled serving
matching UPC/GTIN · checked Jul 25, 2026
View on Brand website ↗Target
Exact UPC/GTIN match$32.99
$1.10 per labeled serving
matching UPC/GTIN · checked Jul 28, 2026
View on Target ↗Walmart
Not confirmedNo exact listing saved
We only show a price when the seller publishes the same barcode as the bottle. We haven’t found that match here.
Search Walmart ↗Same UPC/GTIN observed across 4 sellers. Amazon was lowest at $29.95; Target was highest at $32.99 — a $3.04 range at check time.
The observed listing and exact brand page repeat 2,000 mg. That confirms cross-page consistency of the published claim, not the product contents.
Reference prices only · no affiliate links · every compared seller must publish the matching UPC/GTIN.
Want to inspect the evidence?
The full report shows every source, the exact unresolved question, and the documentation that would settle it.
Record built September 03, 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.