How much elemental iron is in a 325mg dose of ferrous sulfate (iron supplement)?

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Elemental Iron Content in Ferrous Sulfate 325 mg

A 325 mg ferrous sulfate tablet contains 65 mg of elemental iron. 1

Detailed Information on Ferrous Sulfate Iron Content

Ferrous sulfate is one of the most commonly prescribed oral iron preparations for the treatment of iron deficiency anemia. The elemental iron content varies depending on the specific formulation:

  • Ferrous sulfate 325 mg contains 65 mg of elemental iron 1
  • This provides approximately 362% of the U.S. recommended daily intake (RDI) of iron for adults and children 4 years and older 1

Comparison with Other Iron Preparations

According to clinical guidelines, different iron salt preparations contain varying amounts of elemental iron:

Formulation Preparation Dose Elemental Iron
Ferrous sulfate Tablet 200 mg 65 mg
Ferrous sulfate MR tablet 325 mg 105 mg
Ferrous sulfate MR capsule 150 mg 48 mg
Ferrous gluconate Tablet 300 mg 37 mg
Ferrous fumarate Tablet 210 mg 69 mg
Ferrous fumarate Tablet 322 mg 106 mg

2

Clinical Implications

The elemental iron content is important for dosing considerations:

  • For treatment of iron deficiency anemia, guidelines recommend 50-100 mg of elemental iron daily 2
  • A single 325 mg ferrous sulfate tablet provides 65 mg of elemental iron, which falls within this recommended range
  • When prescribing iron supplements, clinicians should consider the elemental iron content rather than the total weight of the compound

Dosing Considerations

For optimal absorption and effectiveness:

  • Iron is best absorbed when taken on an empty stomach
  • Food can reduce iron absorption by up to 50% if taken within 2 hours before or 1 hour after an iron supplement 2
  • Common side effects include gastrointestinal symptoms like nausea, constipation, and diarrhea

Important Note on Modified Release Formulations

It's worth noting that modified release (MR) ferrous sulfate 325 mg tablets contain a higher amount of elemental iron (105 mg) compared to standard ferrous sulfate 325 mg tablets (65 mg) 2. This distinction is important when prescribing specific formulations.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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