Best Iron Bisglycinate 2026: Ranked by Dose & Cost

By Erin Rose · Published September 19, 2026 · Reviewed against primary sources · Methodology · About Us

Not medical advice. Iron is the one common supplement that can do harm when you do not need it: do not start it without a ferritin or hemoglobin result, keep it away from children, and stop if you have hemochromatosis. This page summarizes the dosing trials, the labels manufacturers file with the NIH, and current Amazon prices.

Not sure you need iron at all? Start with the ferritin test and deficiency signs. Comparing forms? Ferrous sulfate vs bisglycinate →

The three rules that decide an iron bisglycinate

1. One capsule, one whole dose, inside the safe range. The Supplement Facts “Iron” row is elemental iron. A useful capsule carries at least the 18 mg RDA for menstruating women and no more than the 45 mg adult upper limit, so nobody halves a pill or doubles one. The bisglycinate evidence is built on 25 mg: in a randomized trial of 80 pregnant women, 25 mg of iron as ferrous bisglycinate prevented iron deficiency and anemia as effectively as 50 mg as ferrous sulfate, with fewer gastrointestinal complaints (Milman 2014, PMID 24152889). All 3 buyable products we track pass.

2. Prefer a label someone else has tested. Iron products are dosed in milligrams where a factory error matters, and a USP Verified or NSF mark is the only evidence on the shelf that a third party checked the contents. 2 of the 3 products passing rule 1 carry one: Thorne Iron Bisglycinate 25 mg (NSF Certified for Sport) and MegaFood Blood Builder (NSF Certified). NSF Certified for Sport additionally screens each lot for banned substances.

3. Then the lowest cost per dose. Because the absorption trials favour one dose every other day (below), the honest unit is cost per dose, and a bottle lasts twice as long as its serving count suggests. Across the 3 products the spread is 3.0×, from $0.11 to $0.32 a dose, or $1.59 to $4.83 a month at 15 doses.

Every iron bisglycinate we track, ranked by cost per dose

Doses are the elemental iron on each product’s Supplement Facts panel; prices are the current Amazon price for the exact container. Cost per dose is the price divided by servings; the monthly figure assumes one dose every other day.

Per milligram of iron the order is the same: NOW Foods Iron 36 mg Double Strength at $0.003 per mg against $0.012 for MegaFood Blood Builder. Solgar Gentle Iron (Iron Bisglycinate) 25 mg, the other widely sold 25 mg bisglycinate, is not currently buyable on Amazon and is left out of the ranking until it is.

Which iron bisglycinate to buy

Product links go to Amazon and we may earn a commission if you buy. It never changes which product we pick or what we say about it. How we choose.

Best overall

Thorne Iron Bisglycinate 25 mg $0.27 per dose

25 mg of elemental iron as bisglycinate in one capsule, 60 capsules, NSF Certified for Sport on the label. The capsule is the trial dose exactly, the mark is the strictest on the page, and at one capsule every other morning a bottle lasts four months for about $4.00 a month. The default for a menstruating woman, a pregnancy with her clinician’s agreement, or anyone whose ferritin came back low and whose stomach has already rejected ferrous sulfate.

Check price →

Best value

NOW Foods Iron 36 mg Double Strength $0.11 per dose

36 mg of elemental iron as Ferrochel bisglycinate per capsule, 90 capsules, 2.5× cheaper per dose than Thorne Iron Bisglycinate 25 mg. The higher capsule sits under the 45 mg limit and suits a confirmed deficiency being treated every other day; it is more than a maintenance dose needs. No third-party mark on the label, so you are trusting the maker’s own testing.

Check price →

With cofactors

MegaFood Blood Builder $0.32 per dose

26 mg of elemental iron per tablet with folate, vitamin B12 and vitamin C on the same label, 90 tablets, NSF Certified. The pick when a blood count suggests more than one deficiency, or for someone who wants the vitamin C in the tablet rather than a glass of juice. 1.2× the price of Thorne Iron Bisglycinate 25 mg per dose, so buy it for the cofactors, not for value.

Check price →

We read 168 iron bisglycinate labels: the shelf is dosed sensibly, the naming is not

Original research1,587 iron labels with a milligram iron row retrieved from the NIH Dietary Supplement Label Database; 560 are on-market products sold as iron, and 168 of those name a bisglycinate, Ferrochel or chelate form in the iron row, from 96 brands. Every figure was recomputed in both halves of the read order; 11 of 12 held and only those are printed.

The median bisglycinate label directs 25 mg of elemental iron per serving and 25 mg per day, with the middle half of the shelf between 15 and 28 mg. 73.8% reach the 18 mg RDA per serving and only 3.6% direct more than the 45 mg daily limit, so unlike calcium or magnesium this is a shelf that mostly respects its own ceiling. 26.2% of labels need two or more units per serving. Where the shelf misleads is language: 13.7% of labels sold on the bisglycinate name blend it with another iron form, and only 5.4% actually use the word “gentle” that the category is marketed under, so neither the name nor its absence tells you what is in the capsule.

Bisglycinate against ferrous sulfate: what the trials measured

Ferrous sulfate is the cheap, effective standard, and it is genuinely hard on the gut: a systematic review and meta-analysis of 43 trials found it caused significantly more gastrointestinal side effects than placebo, and more than intravenous iron (Tolkien 2015, PMID 25700159). Bisglycinate’s case is that it does the same job at a lower dose with less of that. The Milman trial above matched 50 mg of sulfate with 25 mg of bisglycinate in pregnancy (Milman 2014, PMID 24152889); in Mexican schoolchildren given 30 mg a day of either form for 12 weeks, ferritin was higher in the bisglycinate group six months later (Duque 2014, PMID 25023784); and the 2023 systematic review and meta-analysis of randomized trials concluded bisglycinate improved hemoglobin at least as well as other forms at lower doses, with fewer gastrointestinal effects in pregnant women and no clear difference in children, while noting that several trials were industry-funded (Fischer 2023, PMID 36728680). And across two randomized pregnancy studies comparing low, equipotent doses of fumarate, bisglycinate and sulfate, none produced clinically significant gastrointestinal complaints (Milman 2024, PMID 39582678).

What bisglycinate does not do is absorb two or three times better, whatever the marketing says. Its advantages are tolerability, a lower effective dose, and resistance to the food and mineral inhibitors that cut sulfate absorption. The full head-to-head, including cost per course, is at ferrous sulfate vs bisglycinate.

Every other day: the schedule matters more than the salt

A single oral iron dose raises the hormone hepcidin for about 24 hours, and hepcidin shuts the door on the next dose. In iron-depleted women, fractional absorption was 21.8% when doses were given on alternate days against 16.3% on consecutive days, and a single morning dose beat a split dose (Stoffel 2017, PMID 29032957); the underlying hepcidin mechanism was shown the same way with daily and twice-daily dosing (Moretti 2015, PMID 26289639). The result held in women with iron-deficiency anemia, not just depletion (Stoffel 2020, PMID 31413088), and a 2024 systematic review of alternate-day versus daily therapy in iron-deficiency anemia found no significant difference in hemoglobin and fewer side effects, especially nausea and altered bowel habits, on the alternate-day schedule (Kamath 2024, PMID 37979057). The American Gastroenterological Association’s 2024 practice update says the same: give oral iron once a day at most, every-other-day dosing may be better tolerated with similar absorption, and add vitamin C; it also states that no oral formulation has an advantage over another and prefers ferrous sulfate as the cheapest, which is the honest counterweight to everything on this page (DeLoughery 2024, PMID 38864796).

Practically: one capsule of the pick, every other morning, with water or vitamin C, an hour before coffee and away from calcium and dairy. Recheck ferritin after eight to twelve weeks; iron is not a supplement to take indefinitely on a hunch. See best time to take iron, is 25 mg enough and iron for anemia and low ferritin.

Frequently asked questions

Related guides

• Iron: forms, dose and what to buy
• Ferrous sulfate vs bisglycinate
• Solgar vs Thorne iron bisglycinate
• Iron dosage guide
• Iron for women
• Liquid iron
• Best iron supplement, all forms

Sources