What is the recommended iron supplementation dose for a patient with severe iron deficiency anemia and a hemoglobin (Hgb) level of 8 g/dL?

Iron Supplementation for Severe Iron Deficiency Anemia (Hemoglobin 8 g/dL)

For a patient with hemoglobin of 8 g/dL, intravenous iron should be considered as first-line therapy given the severity of anemia (Hgb <10 g/dL), with a target dose of 1000 mg total elemental iron administered according to product-specific protocols. 1

Initial Treatment Selection

Intravenous iron is preferred over oral iron when hemoglobin is below 10 g/dL because:

• The severity of anemia requires faster hemoglobin response 1
• Oral iron absorption is limited and may be insufficient when blood loss or iron deficit is substantial 2
• IV iron demonstrates superior efficacy with hemoglobin improvements of 3.2 g/dL versus slower oral responses 1

If Oral Iron Is Chosen Despite Low Hemoglobin

If clinical circumstances favor oral therapy, the dosing strategy should be:

Start with 100-120 mg elemental iron given as a single morning dose on alternate days 3, 4:

• Doses ≥60 mg stimulate hepcidin elevation that persists 24 hours, blocking iron absorption from subsequent doses 4
• Alternate-day dosing maximizes fractional absorption while reducing gastrointestinal side effects 4
• Morning administration is superior to afternoon/evening dosing due to circadian hepcidin patterns 4

Traditional high-dose regimens (ferrous sulfate 200 mg three times daily = 180-195 mg elemental iron daily) are outdated 1, 5:

• These regimens are based on poor-quality evidence from a single small study 5
• Multiple daily doses increase side effects without improving absorption 3
• Unabsorbed iron causes gut inflammation and reduces compliance 4

Intravenous Iron Dosing

For IV iron, administer 1000 mg total elemental iron empirically, or calculate using body weight and hemoglobin deficit 1:

Simple Dosing Scheme (Preferred)

• Hemoglobin <10 g/dL: Give 1000 mg total elemental iron 1
• This simple scheme shows better efficacy and compliance than formula-based calculations 1
• For hemoglobin <7 g/dL, consider an additional 500 mg 1

Product-Specific Administration

• Ferric carboxymaltose: 500-1000 mg per dose (up to 20 mg/kg), can be given over 15 minutes 1
• Iron sucrose: 200-300 mg per treatment episode, requires multiple doses 1
• Ferric gluconate (Ferrlecit): 125 mg diluted in 100 mL saline over 1 hour per session 6

Monitoring Response

Reassess hemoglobin at 4 weeks to determine treatment adequacy 1:

• Expected response: Hemoglobin increase ≥2 g/dL within 4 weeks 1
• For oral iron: Hemoglobin increase <1.0 g/dL at 2 weeks predicts oral iron failure and should prompt transition to IV iron 7
• This 2-week checkpoint has 90.1% sensitivity and 79.3% specificity for identifying oral iron non-responders 7

Treatment Goals and Duration

Target hemoglobin: 12-13 g/dL (sex-dependent) 3:

• Target ferritin: >100 ng/mL to adequately replenish stores 3
• Continue iron supplementation for 3 months after hemoglobin correction to replenish body stores 1

Common pitfall: Stopping treatment when hemoglobin normalizes without replenishing iron stores leads to rapid recurrence 3

Failure to Respond

If hemoglobin does not increase appropriately, evaluate for:

• Non-compliance (most common with oral iron due to side effects) 1
• Ongoing blood loss exceeding iron replacement capacity 1, 2
• Malabsorption (celiac disease, inflammatory bowel disease, prior gastric surgery) 1
• Misdiagnosis or coexisting causes of anemia (vitamin B12 deficiency, anemia of chronic disease) 1, 3

Safety Considerations

Monitor for hypersensitivity reactions during and for 30 minutes after IV iron administration 6:

• Personnel and therapies for treating anaphylaxis must be immediately available 6
• IV iron may cause hypotension; monitor blood pressure during infusion 6

Avoid iron overload: Regularly monitor hematologic parameters and do not administer to patients with iron overload 6