Thorne Iron Bisglycinate 25 mg Review
#1 of 9 · Best Overall✓ Label verified · Supplement Facts read Sep 7, 2026Real retailer photo, cut out. Label unedited.
Buy it. The one iron bottle worth trusting for confirmed deficiency. You get the gentlest non-heme form, a dose that genuinely replenishes ferritin, and the strongest third-party credential on the shelf — a product-level NSF Certified for Sport seal.
~$14.00~$0.23
Why It Scores 9.2 — And The Label Line Behind Each Number
Form & Bioavailability
30% of scoreFerrous bisglycinate (Ferrochel) is a chelated non-heme form that absorbs well and, in a randomized pregnancy trial, matched double the dose of ferrous sulfate for preventing deficiency (Milman 2014). Only heme iron scores higher on pure absorption.
- Form
- Ferrous bisglycinate chelate (Ferrochel)
Dose Appropriateness
20% of score25 mg elemental in one capsule is a true repletion-level dose for correcting a confirmed deficiency — high enough to raise ferritin, not so high it guarantees gut upset.
GI Tolerance & Safety
20% of scoreBisglycinate is the category's gentlest oral form; the trial evidence shows fewer GI complaints than ferrous salts (Milman 2014, Tolkien 2015). Iron still warrants ferritin-guided use, not indefinite dosing.
Third-Party Testing & Purity
20% of scoreCarries a product-level NSF Certified for Sport seal — banned-substance tested on the finished product, not just a GMP facility claim. Gluten, dairy and soy free. The strongest verification in the set.
- Third-party
- NSF Certified for Sport (product-level)
Value per Serving
10% of scoreAt roughly $0.23 per capsule it is fair for a practitioner-tier brand, but the 60-count runs out fastest and costs far more per milligram than the bulk chelate picks.
- Size
- 60 capsules (60 servings)
- Serving
- 1 capsule daily
- Price (approx.)
- ~$14.00
- Cost / serving
- ~$0.23
- More Specs
- Elemental iron
- 25 mg per capsule
- Free-from
- Gluten, dairy & soy
Label verified. Every figure read from the Supplement Facts photo, Sep 7, 2026.
Marketing Claims Vs. Reality
Ferrous bisglycinate is gentler and less constipating than ferrous salts
In a randomized trial, 25 mg bisglycinate matched 50 mg ferrous sulfate for preventing deficiency with fewer GI complaints (Milman 2014, PMID 24152889); a meta-analysis confirms ferrous sulfate roughly doubles GI side-effect risk (Tolkien 2015, PMID 25700159).
25 mg is a true repletion dose, one capsule daily
25 mg elemental sits squarely in the therapeutic repletion range for oral iron; a chelate at this dose measurably raised ferritin in the comparative literature (Name 2018, PMID 30280670).
Carries a product-level NSF Certified for Sport seal
NSF Certified for Sport is a finished-product certification that tests for banned substances and label accuracy — a genuinely product-level credential, not a facility-only GMP claim. Thorne is long-established in this program.
Free of gluten, dairy and soy
Consistent with the product's stated free-from panel; a plausible, low-risk formulation claim for a single-ingredient chelate capsule.
What Our Test Actually Found
The form does the heavy lifting
Iron supplements fail less on potency than on tolerance — people stop taking them because of nausea and constipation. Bisglycinate is chelated so it is largely shielded from the gut irritation that ferrous salts cause, which is why a 25 mg chelate dose can outperform a larger salt dose in practice (Milman 2014).
The only real product-level seal here
Most 'third-party tested' iron means batch testing or a GMP facility. NSF Certified for Sport is different: it certifies the finished product for banned substances and label accuracy. If you compete in a tested sport, this is the single most important line on the label.
A repletion tool, not a daily vitamin
25 mg is designed to correct a deficit, not to be taken forever. The honest instruction is to confirm you are low first, dose for a defined window, then retest ferritin and stop. Over-supplementing iron with normal stores is not benign.
Practitioner quality at a mainstream price
Thorne sits in the clinician channel, yet this bottle lands around $14. You are paying a modest premium over bulk brands for the certification and QC — not for a different or better iron molecule.
Full analysis: all pros & cons (7), buy if / skip if
- Ferrochel bisglycinate — the gentle, non-constipating form
- Only pick with a product-level NSF Certified for Sport seal
- 25 mg is a true repletion dose in one daily capsule
- Practitioner-tier brand at a mainstream price (~$14)
- Free of gluten, dairy and soy
- 25 mg is a repletion dose — use ferritin-guided, not as an indefinite daily top-up
- 60-count runs out fastest and costs most per milligram among the value picks
- You have a confirmed low ferritin or diagnosed iron deficiency
- You want the best-tolerated form and are willing to pay a small premium for it
- You want banned-substance testing (athletes, tested competitors)
- You value a single once-daily capsule over splitting doses
- You just want a low-dose maintenance top-up (18 mg NOW Foods fits better)
- You want the lowest possible cost per capsule (Nutricost is a third the price)
You get the gentlest non-heme form, a dose that genuinely replenishes ferritin, and the strongest third-party credential on the shelf — a product-level NSF Certified for Sport seal. The only discipline it asks of you is to retest ferritin and stop once you are replete.
If you have a confirmed low ferritin and want one bottle you can trust without a second thought, this is it. Thorne pairs the best-tolerated non-heme form — ferrous bisglycinate (Ferrochel) — with a 25 mg elemental dose that actually moves iron stores, and it is the rare iron supplement carrying a product-level third-party certification rather than a generic facility claim.
The default answer for confirmed low iron
If you have documented low iron and want one bottle to trust, this is the pick: the best-tolerated non-heme form, a dose that actually raises ferritin, and the rarest thing on an iron shelf — a product-level third-party seal. Retest ferritin and stop once you are replete.
If This Doesn’t Fit — Try These
02Nutricost Iron Bisglycinate
Our take: the smart-money buy.
03MegaFood Blood Builder
Our take: for menstruating women — where iron, folate and B12 shortfalls travel together — the cofactor blend is a genuine edge over plain iron.
04Solgar Gentle Iron
Our take: a rock-solid, widely-stocked gentle chelate you can grab almost anywhere.
Quick Answers
Should I take this every day forever?
No. 25 mg is a repletion-level dose meant to correct a confirmed deficiency over a defined window. Retest ferritin with your clinician and stop once you are replete — routine iron with normal stores is not advisable.
Will it upset my stomach like other iron pills?
Far less likely. Bisglycinate is the gentlest common oral form, and the trial evidence shows notably fewer GI complaints than ferrous sulfate. Taking it with food and, if needed, every other day can improve tolerance further.
Is the NSF Certified for Sport seal actually meaningful?
Yes — it is a finished-product certification that screens for banned substances and confirms label accuracy, which is stronger than a generic 'GMP facility' or 'third-party tested' statement. It matters most if you are a tested athlete.
Why pay more than Nutricost for the same molecule?
You are paying for the product-level NSF certification and Thorne's QC, not a superior iron form. If banned-substance testing is not important to you, Nutricost's identical bisglycinate is the value play.
Sources & Further Reading
3 peer-reviewed sources, each linked to PubMed
- [1] Milman N, et al. J Perinat Med. 2014;42(2):197-206. PMID 24152889 — Ferrous bisglycinate 25 mg iron is as effective as ferrous sulfate 50 mg iron in the prophylaxis of iron deficiency and anemia during pregnancy in a randomized trial. 25 mg bisglycinate matched 50 mg ferrous sulfate for preventing deficiency, with fewer gastrointestinal complaints.
- [2] Tolkien Z, et al. PLoS One. 2015;10(2):e0117383. PMID 25700159 — Ferrous sulfate supplementation causes significant gastrointestinal side-effects in adults: a systematic review and meta-analysis. Ferrous sulfate roughly doubled GI side-effect risk versus placebo (OR 2.32), establishing the tolerance gap chelates close.
- [3] Name JJ, et al. Curr Pediatr Rev. 2018;14(2):123-129. PMID 30280670 — Iron Bisglycinate Chelate and Polymaltose Iron for the Treatment of Iron Deficiency Anemia: A Pilot Randomized Trial. Only the iron bisglycinate chelate significantly raised ferritin and mean corpuscular hemoglobin over 45 days.
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