How do I order 325 mg of iron for a patient?

How to Order 325 mg of Iron

To order 325 mg of iron, prescribe ferrous sulfate 325 mg tablets, which provides approximately 65 mg of elemental iron per tablet. 1

Understanding Iron Formulations and Elemental Iron Content

When ordering iron supplements, it's critical to understand the difference between the total tablet weight and the actual elemental iron content:

• Ferrous sulfate 325 mg tablet = 65 mg elemental iron 1
• Ferrous fumarate 325 mg tablet = 106-108 mg elemental iron 1
• Ferrous gluconate 325 mg tablet = 35-37 mg elemental iron 1

Prescription Writing Guidelines

When writing the prescription:

1. Specify "Ferrous sulfate 325 mg tablets"
2. Include dosing frequency (typically once to three times daily)
3. Specify duration (typically 3 months for iron deficiency anemia)
4. Include instructions to take on empty stomach (1 hour before or 2 hours after meals)

Example prescription: "Ferrous sulfate 325 mg PO daily (or BID) for 3 months. Take on empty stomach."

Dosing Considerations

The standard therapeutic dose for iron deficiency is 200 mg of elemental iron per day, divided into 2-3 doses 1, 2. This would equate to:

• Ferrous sulfate 325 mg: 3 tablets daily (195 mg elemental iron)
• Ferrous fumarate 325 mg: 2 tablets daily (212-216 mg elemental iron)
• Ferrous gluconate 325 mg: 6 tablets daily (210-222 mg elemental iron)

Important Clinical Considerations

• Absorption optimization: Instruct patients to take iron on an empty stomach, 1 hour before or 2 hours after meals 2
• Avoid co-administration with calcium supplements, antacids, tea, coffee, or milk as these reduce absorption 2
• Side effect management: If GI side effects occur, consider:
  • Taking with small amounts of food (though this reduces absorption by ~50%)
  • Reducing to once daily dosing
  • Switching to alternate-day dosing
  • Changing to a different iron formulation 1, 2

Monitoring Response

• Check hemoglobin after 2 weeks of therapy - an increase of at least 10 g/L indicates adequate response 1, 2
• Continue iron supplementation for 3 months after hemoglobin normalizes to replenish iron stores 1
• If no response after 2 weeks despite adherence, consider switching to IV iron 2

Common Pitfalls to Avoid

1. Confusing total tablet weight with elemental iron content - always consider the elemental iron when determining dosage
2. Prescribing excessive doses - more than 200 mg elemental iron daily does not improve absorption and only increases side effects 2
3. Not addressing adherence issues - up to 40% of patients discontinue oral iron due to GI side effects 2
4. Inadequate duration of therapy - iron should be continued for 3 months after correction of anemia to replenish stores 1

Remember that ferrous sulfate is the most economical option (approximately £1.00 for a 28-day supply) compared to other formulations, making it the first-line choice for most patients 1, 2.