Form Comparison

Ferrous Fumarate vs Iron Bisglycinate

How ferrous fumarate and iron bisglycinate differ in elemental content, absorption, tolerance, and cost.

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Quick verdict. Fumarate is the cheap, iron-dense salt (33% elemental) in most prenatal vitamins. Bisglycinate is a chelate that phytates affect less and that causes fewer GI complaints in trials, partly because typical doses are lower. Start with fumarate if cost matters and you tolerate it; switch to bisglycinate if constipation or nausea makes you skip doses.

Side by Side

Ferrous Fumarate Iron Bisglycinate
Elemental content 33% elemental iron 20% elemental iron
Absorption High High
How it is absorbed Ferrous iron absorbed by DMT1, as with sulfate. Iron chelated to two glycine molecules. The chelate is less affected by dietary phytates than iron salts, and absorption remains regulated by iron status.
Typical dose 65-106 mg elemental iron per tablet 25-50 mg elemental iron daily
Common uses iron deficiency, prenatal vitamins iron deficiency with GI intolerance to salts, pregnancy
Side effects Similar to sulfate per mg of elemental iron. Typically fewer GI complaints than ferrous sulfate in trials, partly due to lower doses.
Cost Low Moderate
Also called iron fumarate ferrous bisglycinate chelate, Ferrochel, gentle iron
Labels in index 190 283

When to Choose Ferrous Fumarate

Choose ferrous fumarate when you want more iron per tablet. Highest elemental percentage of the common ferrous salts.

Ferrous Fumarate

Choose ferrous fumarate when you want more iron per tablet.

What to look for: Ferrous Fumarate named on the Supplement Facts panel, with the amount per serving stated.

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When to Choose Iron Bisglycinate

Choose iron bisglycinate when ferrous salts cause GI side effects. Often the switch when sulfate causes constipation or nausea.

Iron Bisglycinate

Easier on the stomach for many people. Fewer head-to-head data than sulfate.

What to look for: Elemental iron stated per capsule, often 25-36 mg. Ferrochel is the most studied raw material.

Find on iHerb Affiliate link

Products on Titrate

In Titrate's index of NIH label data, 190 labels named as iron products list ferrous fumarate and 283 list iron bisglycinate.

Open supplement search

Iron does not have its own search category yet. Each product above links to its full label in the NIH database.

Related

References

NIH Office of Dietary Supplements. Iron: Fact Sheet for Health Professionals.

Hallberg L, Brune M, Rossander L. Iron absorption in man: ascorbic acid and dose-dependent inhibition by phytate. Am J Clin Nutr. 1989;49(1):140-144.

Moretti D, et al. Oral iron supplements increase hepcidin and decrease iron absorption from daily or twice-daily doses in iron-depleted young women. Blood. 2015;126(17):1981-1989.

Tolkien Z, et al. Ferrous sulfate supplementation causes significant gastrointestinal side-effects in adults: a systematic review and meta-analysis. PLoS One. 2015;10(2):e0117383.

Stoffel NU, et al. Iron absorption from oral iron supplements given on consecutive versus alternate days and as single morning doses versus twice-daily split dosing in iron-depleted women: two open-label, randomised controlled trials. Lancet Haematol. 2017;4(11):e524-e533.

Stoffel NU, et al. Iron absorption from supplements is greater with alternate day than with consecutive day dosing in iron-deficient anemic women. Haematologica. 2020;105(5):1232-1239.

World Health Organization. WHO guideline on use of ferritin concentrations to assess iron status in individuals and populations. Geneva: WHO; 2020.