No, 18 mg ferrous gluconate is NOT comparable to a 324 mg tablet
A 324 mg ferrous gluconate tablet contains 38 mg of elemental iron, while an 18 mg ferrous gluconate tablet would contain only approximately 2 mg of elemental iron—this is completely inadequate for any therapeutic purpose. 1
Understanding the Critical Difference
Elemental Iron Content
- Ferrous gluconate 324 mg contains 38 mg of elemental iron (approximately 11.7% elemental iron by weight) 1
- An 18 mg ferrous gluconate tablet would contain only ~2 mg of elemental iron—far below any therapeutic threshold
- This 2 mg dose is even less than typical multivitamin preparations, which contain up to 14 mg elemental iron 2
Therapeutic Requirements
- Standard treatment for iron deficiency anemia requires 50-100 mg of elemental iron once daily 2
- To achieve the minimum therapeutic dose of 50 mg elemental iron, you would need approximately 13-14 tablets of the 18 mg ferrous gluconate preparation
- The FDA-approved ferrous gluconate 324 mg tablet provides 38 mg elemental iron per tablet, requiring 1-2 tablets daily to reach therapeutic range 1
Clinical Context for Proper Dosing
Comparison with Standard Iron Preparations
- Ferrous sulfate 200 mg: 65 mg elemental iron 2, 3
- Ferrous fumarate 322 mg: 106 mg elemental iron 2
- Ferrous gluconate 300-324 mg: 35-38 mg elemental iron 2, 1
- Ferrous gluconate 18 mg: ~2 mg elemental iron (inadequate)
Why This Matters for Patient Outcomes
- The British Society of Gastroenterology emphasizes that once-daily dosing of 50-100 mg elemental iron is optimal because higher frequency dosing stimulates hepcidin, reducing iron absorption by 35-45% 2
- An 18 mg ferrous gluconate tablet cannot achieve therapeutic levels even with multiple daily doses
- Inadequate iron supplementation leads to persistent anemia, fatigue, and failure to replenish iron stores—directly impacting quality of life and morbidity 2
Common Pitfall to Avoid
The most critical error is confusing the total salt weight (324 mg ferrous gluconate) with elemental iron content (38 mg). Always prescribe by specifying both the salt form AND the elemental iron content to prevent dosing errors that could leave patients undertreated 3, 4.