How to Pick a Magnesium Glycinate Brand: Reading a Certificate of Analysis

Every magnesium bottle promises the same thing. The difference between an honest brand and a label-printer is one document most shoppers never ask for: the Certificate of Analysis (COA). This short guide makes you the rare buyer who asks.

What a COA is

A COA is a lab report for a specific production batch. It verifies what’s actually in the jar: elemental magnesium content, the glycinate form, and — more importantly — what’s not in it (heavy metals, contaminants). Reputable brands either publish COAs on their website or email them on request. Silence is an answer.

The four things to check

1. Elemental magnesium per serving — matches the label claim (within normal analytical variance). Products that “accidentally” overstate content are common in this category.
2. Heavy metals: lead, arsenic, cadmium, mercury — present in trace amounts in everything; the COA should show them below limits (California Prop 65 or USP standards are common references).
3. The form — genuine glycinate/bisglycinate, not “magnesium oxide blended with a little glycine” dressed up as “chelated.” The ingredient list should say bisglycinate or glycinate chelate, not oxide.
4. Batch and date — a COA for your batch, or at least a recent one. A 3-year-old document proves nothing about what’s on shelves now.

Third-party marks that shortcut the work

Don’t want to read lab documents? Look for these on the label — they represent independent verification programs:

• NSF Certified for Sport — the strictest
• USP Verified — gold standard for content accuracy
• Informed Choice / Informed Sport — common for sports products

A brand with none of these and no published COAs is asking you to trust its printer.

Price reality

Honest glycinate costs more than oxide — that’s normal, oxide is nearly worthless as a supplement. But past a certain point you’re paying for marketing. Our magnesium timing guide covers what matters for effect; this page covers what matters for trust. Both checks take five minutes and put you ahead of 95% of supplement buyers. The full comparison links only categories where you can verify brands yourself.