Form Comparison

Ferrous Fumarate vs Ferrous Gluconate

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

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Quick verdict. These are the same ferrous iron, absorbed by the same transporter, with the same side effects per milligram of elemental iron. The difference is density: fumarate is 33% iron and gluconate 12%, so a fumarate tablet carries roughly three times the iron. Choose fumarate for fewer tablets during repletion and gluconate when you want small per-tablet doses to build tolerance.

Side by Side

Ferrous Fumarate Ferrous Gluconate
Elemental content 33% elemental iron 12% elemental iron
Absorption High High
How it is absorbed Ferrous iron absorbed by DMT1, as with sulfate. Ferrous iron absorbed by DMT1, as with sulfate.
Typical dose 65-106 mg elemental iron per tablet 27-38 mg elemental iron per tablet
Common uses iron deficiency, prenatal vitamins iron deficiency, lower per-tablet dose
Side effects Similar to sulfate per mg of elemental iron. Similar to sulfate per mg of elemental iron; fewer side effects per tablet only because each tablet holds less iron.
Cost Low Low
Also called iron fumarate iron gluconate
Labels in index 190 67

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 Ferrous Gluconate

Choose ferrous gluconate when you want smaller per-tablet iron doses. Lowest elemental percentage of the common ferrous salts.

Ferrous Gluconate

Choose ferrous gluconate when you want smaller per-tablet iron doses.

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

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 67 list ferrous gluconate.

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.