What is the recommended dosage of ferrous sulfate (iron supplement) for a patient with a hemoglobin (Hgb) level of 7.8?

Prescribing Ferrous Sulfate for Hemoglobin 7.8 g/dL

For a patient with hemoglobin of 7.8 g/dL (78 g/L), prescribe ferrous sulfate 325 mg orally once daily or every other day as first-line therapy, but first confirm iron deficiency with ferritin and transferrin saturation, and strongly consider intravenous iron if the patient has active inflammation, malabsorption, ongoing blood loss, or hemoglobin below 10 g/dL (100 g/L). 1, 2

Initial Assessment Required

Before prescribing iron, you must obtain:

• Serum ferritin: Iron deficiency is confirmed when ferritin <30 ng/mL in patients without inflammation, or <100 ng/mL in patients with chronic inflammatory conditions 2
• Transferrin saturation (TSAT): Values <20% indicate iron deficiency 1
• Assess for underlying causes: Gastrointestinal bleeding, menstrual blood loss, malabsorption disorders (celiac disease, post-bariatric surgery), inflammatory bowel disease, chronic kidney disease, heart failure, or cancer 2

Oral Iron Dosing

Standard regimen: Ferrous sulfate 325 mg (containing 65 mg elemental iron) once daily 1, 2

• Alternative dosing: Every-other-day dosing may improve tolerability with similar efficacy 2
• Duration: Continue for 3 months after hemoglobin normalizes to replenish iron stores 1
• Adjunct: Consider adding ascorbic acid (vitamin C) to enhance absorption if response is poor 1

Expected response: Hemoglobin should increase by approximately 2 g/dL after 3-4 weeks of therapy 1

When to Use Intravenous Iron Instead

Intravenous iron is superior and should be first-line in the following situations:

• Hemoglobin <10 g/dL (100 g/L): Your patient with Hgb 7.8 g/dL falls into this category 1
• Active inflammatory conditions: IBD, chronic kidney disease, heart failure, or cancer 1, 2
• Malabsorption: Celiac disease, post-bariatric surgery, atrophic gastritis 2
• Ongoing blood loss: Gastrointestinal or heavy menstrual bleeding 2
• Oral iron intolerance: Previous adverse effects from at least two oral preparations 1, 2
• Pregnancy: Second and third trimesters 2

The ECCO guidelines specifically state that IV iron is more effective, shows faster response, and is better tolerated than oral iron in these contexts 1

Dosing for Specific Populations

For inflammatory bowel disease patients (if applicable):

• Body weight <70 kg with Hgb 70-100 g/L: 1500 mg total IV iron 1
• Body weight ≥70 kg with Hgb 70-100 g/L: 2000 mg total IV iron 1

For chronic kidney disease patients (if applicable):

• Target ferritin ≥100 ng/mL and TSAT ≥20% 1
• In patients with Hgb <100 g/L and ferritin <100 ng/mL, expect hemoglobin increases of 4-7 g/L with oral iron or 7-10 g/L with IV iron 1

Monitoring and Follow-Up

• Recheck hemoglobin and iron indices at 3-4 weeks 1

• Failure to respond (Hgb increase <2 g/dL by 3-4 weeks) indicates:

  • Poor compliance 1
  • Continued blood loss 1
  • Malabsorption 1
  • Misdiagnosis (not iron deficiency) 1
  • Underlying tumor progression or other causes 1

• After correction: Monitor hemoglobin every 3 months for one year, then annually 1

• Restart iron if hemoglobin or MCV falls below normal 1

Critical Pitfalls to Avoid

Do not transfuse based solely on hemoglobin threshold: At Hgb 7.0 g/dL, transfusion does not improve organ dysfunction compared to no transfusion in stable patients 3. Focus on correcting iron deficiency as the underlying cause.

Do not delay investigation of underlying cause: While treating with iron, simultaneously investigate the source of iron loss, particularly gastrointestinal bleeding in patients over 45 years or those with alarm symptoms 1

Do not use parenteral iron without documented intolerance or contraindication to oral iron unless the patient meets criteria above, as it is more expensive and carries risk of anaphylaxis 1

Be aware of HbA1c interference: If the patient has diabetes, iron deficiency anemia falsely elevates HbA1c by approximately 0.4%, which will decrease after iron repletion 4