What is the treatment for an adult with severe iron deficiency anemia?

Severe Iron Deficiency Anemia: Treatment Approach

You need immediate iron replacement therapy with oral ferrous sulfate 325 mg (65 mg elemental iron) daily, plus urgent bidirectional endoscopy (upper and lower GI tract) to identify the source of blood loss, as your iron saturation of 3% with markedly elevated TIBC indicates severe absolute iron deficiency that requires both treatment and investigation for potentially life-threatening causes like GI malignancy. 1, 2

Immediate Iron Replacement

Start oral iron therapy immediately—do not wait for endoscopy results. 2

• Prescribe ferrous sulfate 325 mg (65 mg elemental iron) once daily as first-line therapy 2, 3
• If gastrointestinal side effects occur (nausea, constipation, abdominal pain), reduce to one tablet every other day rather than discontinuing—this maintains efficacy while improving tolerability 2
• Expect hemoglobin to rise ≥10 g/L within 2 weeks if true iron deficiency; this response confirms the diagnosis even with equivocal labs 1
• Continue therapy for 3-6 months minimum to replenish iron stores, not just correct hemoglobin 4

When to Use Intravenous Iron Instead

Switch to IV iron if: 2, 5

• Oral iron not tolerated despite alternate-day dosing
• No adequate response after 4 weeks of oral therapy
• Active inflammatory conditions present (check CRP)
• Ongoing blood loss exceeds absorption capacity
• Malabsorption suspected (celiac disease, post-bariatric surgery, atrophic gastritis)

Mandatory Investigation for Underlying Cause

Your iron studies demand urgent GI evaluation—this degree of iron deficiency in adults almost always indicates pathologic blood loss. 1

Required Endoscopic Evaluation

All adults with iron saturation <20% and elevated TIBC need bidirectional endoscopy: 1

• Upper endoscopy with small bowel biopsies (to exclude celiac disease, gastric cancer, angiodysplasia) 1
• Colonoscopy (to exclude colorectal cancer, inflammatory bowel disease, angiodysplasia) 1
• This applies to both men and postmenopausal women universally; for premenopausal women, consider if age >40 years or heavy menstrual bleeding doesn't fully explain severity 1, 4

Critical Pitfall to Avoid

Never assume dietary deficiency as the primary cause in adults—chronic disease and GI bleeding (including occult malignancy) are far more common causes of this degree of iron deficiency 2. Your TIBC of 501 (markedly elevated) indicates true iron deficiency, not anemia of chronic disease.

If Initial Endoscopy is Negative

For persistent or recurrent iron deficiency after negative upper and lower endoscopy: 2, 4

• Investigate the small bowel with capsule endoscopy (preferred) or CT/MR enterography 2
• Look for angioectasias (most common), inflammatory disease, or small bowel neoplasms 2
• Consider long-term iron replacement therapy as appropriate strategy when cause is unknown or irreversible 2

Monitoring Response

Check hemoglobin in 2 weeks: 1

• Rise of ≥10 g/L confirms iron deficiency and adequate response
• If no response, reassess for malabsorption, ongoing blood loss, or incorrect diagnosis
• Once hemoglobin normalized, continue iron for 3-6 months to replenish stores 4

Monitor for recurrent iron deficiency every 3 months for at least one year after correction, especially if inflammatory bowel disease or other chronic conditions present 1

Special Considerations

Your transferrin saturation of 3% (normal >20%) with TIBC of 501 (elevated) confirms absolute iron deficiency, not functional iron deficiency or anemia of chronic disease 1. This pattern demands investigation regardless of hemoglobin level, as even non-anemic iron deficiency with these parameters warrants evaluation in adults 1.

Do not use high-dose oral iron regimens—100 mg elemental iron daily is as effective as higher doses with significantly fewer side effects 2. The standard 325 mg ferrous sulfate tablet (65 mg elemental iron) is appropriate 3.