Iron (Ferrous Fumarate)
Also known as: ferrous fumarate, iron(II) fumarate, iron fumarate
A ferrous salt of fumaric acid that carries about 33% elemental iron, the highest of the common iron forms, which keeps tablets small. It is less water-soluble than ferrous sulfate and dissolves mainly in gastric acid, with bioavailability judged comparable to sulfate in adults and somewhat lower in young children. It is a common choice in prenatal tablets and fortified products where iron content per gram matters.
Research summary
Supplies ferrous iron after dissolution in gastric acid for hemoglobin and myoglobin synthesis.
Dosage
Daily amounts, elemental (33% of the compound is the element).
| Lowest studied | Typical range | Highest studied | Upper limit |
|---|---|---|---|
| 15 mg | 18–45 mg | 45 mg | 45 mg |
NIH ODS — UL of 45 mg/day for adults; higher amounts are used only under medical supervision
Doses are elemental iron. Take with a small amount of food if nausea or constipation occurs; avoid taking with calcium, tea, or antacids. Deficiency protocols use higher doses under supervision, but the app caps at the 45 mg UL. Ferrous fumarate (MW 169.9) is ≈ 33% Fe. Keep out of reach of children.
Source material: synthetic (ferrous sulfate reacted with sodium fumarate)
As supplied: ≈ 33% Fe; 18 mg elemental ≈ 55 mg compound
Forms of Iron
| Form | Typical dose | Element % | Formats | Price |
|---|---|---|---|---|
| Iron (Ferrous Fumarate) | 18–45 mg | 33% | Capsule, Tablet, Powder | low |
| Iron Bisglycinate | 18–30 mg | 20% | Capsule, Powder, Tablet, Gummy, Liquid | mid |
| Iron (Ferrous Sulfate) | 18–45 mg | 20% | Capsule, Tablet, Liquid | low |
Format suitability
- Capsule
- Powder
- Tablet
- Softgel
- Gummy
- Liquid
Compact reddish-brown powder with little taste, so it compresses well into small tablets. Poor water solubility rules out clear liquids.
Formulation notes
Vitamin C taken in the same serving raises non-heme iron absorption and is the classic pairing. Separate from calcium, zinc of 25 mg or more, tea, coffee, and antacids by about two hours. Iron lowers absorption of levothyroxine, tetracyclines, quinolones, and levodopa.
- Has an upper limit
Sources
- Iron — Health Professional Fact SheetNIH ODS
- A comparison of the bioavailability of ferrous fumarate and ferrous sulfate in non-anemic Mexican women and children consuming a sweetened maize and milk drink (Harrington 2011)PubMed
- 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 (Stoffel 2017)PubMed
Related ingredients
Iron Bisglycinate
MineralFerrous iron chelated with two glycine molecules, the form most prenatal and gentle-iron products now use.
Typical: 18–30 mg
Iron (Ferrous Sulfate)
MineralThe reference iron salt used in most clinical research and public-health programs, inexpensive and reliably absorbed.
Typical: 18–45 mg
Potassium Iodide
MineralThe standard iodine source in multivitamins, prenatals, and thyroid-support formulas, about 76.5% iodine by weight and absorbed almost completely.
Typical: 150–300 mcg
Vitamin B6 (Pyridoxine HCl)
VitaminPyridoxine hydrochloride is the standard, inexpensive, and highly stable form of vitamin B6 used in nearly all multivitamins and B-complex products.
Typical: 1.7–50 mg
Kelp (Iodine)
MineralBrown seaweed, usually Laminaria or Ascophyllum species, used as a whole-food iodine source in thyroid and multimineral formulas.
Typical: 150–300 mcg