Elemental Iron Content in 325mg Ferrous Sulfate
A 325mg ferrous sulfate tablet contains 65mg of elemental iron. 1
Standard Conversion Formula
- Ferrous sulfate 325mg (also listed as 324mg in some formulations) provides 65mg of elemental iron, which represents approximately 32.5% elemental iron content by weight 2, 1
- This is the standard immediate-release formulation used in clinical practice 3
Important Prescribing Distinction
You must specify whether you are prescribing standard or modified-release ferrous sulfate, as the elemental iron content differs dramatically:
- Standard ferrous sulfate 325mg = 65mg elemental iron 2, 3, 1
- Modified-release ferrous sulfate 325mg = 105mg elemental iron 3
This discrepancy can lead to significant dosing errors if the formulation type is not clearly specified on the prescription 4, 3
Comparison with Other Iron Salts (All 325mg Tablets)
- Ferrous fumarate 325mg = 108mg elemental iron 2, 3
- Ferrous gluconate 325mg = 35mg elemental iron 2, 3
- Ferrous sulfate 325mg = 65mg elemental iron 2, 1
Clinical Dosing Context
- The recommended therapeutic dose for iron deficiency anemia is 50-100mg elemental iron once daily 4, 3
- A single 325mg ferrous sulfate tablet (65mg elemental iron) falls within this optimal range and is appropriate for once-daily dosing 4
- Doses ≥60mg elemental iron stimulate hepcidin elevation that persists 24 hours and blocks absorption of subsequent doses, making multiple daily doses counterproductive 4, 3
Common Pitfall to Avoid
Never assume all "325mg" iron tablets contain the same amount of elemental iron—the salt form (sulfate vs. fumarate vs. gluconate) and formulation type (standard vs. modified-release) dramatically affect elemental iron content 4, 3