Deep Dive: Our v2 Magnesium Bisglycinate Purity & Composition
I wanted one thing: a magnesium bisglycinate capsule that was pure, properly dosed, and gentle on the gut—no fillers, no vague claims. I started the company so people could confidently recommend a supplement to friends and family that worked and wasn’t a waste of money.
What Went Wrong With Batch #1
Our very first run missed the mark. The raw material we—and many top brands—bought as “magnesium bisglycinate” wasn’t fully magnesium bisglycinate at all.
The Elephant in the Room
Our goal for Batch #1 was zero magnesium oxide. We thought we hit it. In reality, achieving absolutely no oxide appears impossible in today’s supply chain—unless you’re willing to fudge the numbers. We’re not. We’d rather show exactly what’s in every capsule, even if it looks less impressive on the label, because the integrity of the testing matters more than juicing up a marketing claim.
The Bigger Problem
A typical label might read “Magnesium Bisglycinate — 120 mg.”
Most people assume that means 120 mg of actual magnesium bisglycinate. In truth you may get closer to 90 mg of magnesium from bisglycintate, with the balance made up of cheaper forms that absorb poorly and can upset your stomach.
What the Lab Tests Showed
In developing Batch #2, we asked ourselves how we could set a higher standard. The first step was not to rely on a "Certificate" of Analysis from a raw material supplier. (What does it certify exactly if it's false?) We spent weeks and thousands of dollars testing the different raw materials that were available to us. Here's what we found:
| Sample | What the supplier claimed | What the lab found |
|---|---|---|
| A – generic 12‑14% | 100% pure magnesium bisglycinate | 60.7 % pure (lab results here) |
| B – “gold‑standard” brand 10% | 100% pure magnesium bisglycinate | 76.6 % pure (lab results here) |
| C – "fortified" generic 20% | No purity claim; “fortified” with magnesium oxide | 85.3 % pure (lab results here) |
Yes—the one that didn’t claim to be pure was the best of the bunch.
When we pressed the “gold‑standard” Supplier B on how they measure purity, they admitted they don’t test purity at all. They just calculate theoretical numbers from paperwork and measure total magnesium (regardless of whether it is oxide or bisglycinate or another form).
How We Fixed It (and Keep Improving)
- New sourcing: We chose Sample C’s material—the highest‑purity lot we could verify.
- Dose you can trust: Each size 00 capsule now contains 800 mg of magnesium bisglycinate powder, delivering 160 mg of elemental magnesium—136 mg confirmed as magnesium bisglycinate and the rest from oxide. Not ideal, but currently the cleanest raw material we can prove.
- Third‑party tests, every batch: We publish the full lab report so you can see the numbers yourself. Tap the bottle with your phone to access the lab results.
- Open to v3: If someone proves a cleaner, better process, we’ll adopt it—and tell you.
The Bottom Line
Most brands don’t hide the truth on purpose; they simply trust the paperwork. We learned the hard way that isn’t enough. If you’ve been taking magnesium without feeling the benefits, the capsule—not you—might be the issue.
We built Arrow to change that.
— Jason
Founder, Arrow Supplements