How should iron deficiency without anemia be treated?

Treatment of Iron Deficiency Without Anemia

Iron deficiency without anemia should be treated with oral ferrous sulfate 200 mg once daily when ferritin is <30 ng/mL (or <100 ng/mL in the presence of inflammation) and transferrin saturation is <20%, even in the absence of anemia. 1, 2

Diagnostic Confirmation

Iron deficiency without anemia is defined by:

• Ferritin <30 ng/mL in patients without inflammation 1, 3
• Ferritin <100 ng/mL with transferrin saturation <20% when inflammation is present 1, 4
• Normal hemoglobin (≥12 g/dL in women, ≥13 g/dL in men) 1, 2

The condition affects approximately 14% of adults in the US and is at least twice as common as iron deficiency anemia. 2, 5 Patients may experience fatigue, irritability, depression, difficulty concentrating, restless legs syndrome (32–40%), pica (40–50%), dyspnea, and exercise intolerance despite normal hemoglobin. 2, 5

First-Line Oral Iron Therapy

Prescribe ferrous sulfate 200 mg (≈65 mg elemental iron) once daily on an empty stomach. 1, 2 Once-daily dosing is superior to multiple daily doses because hepcidin remains elevated for approximately 48 hours after iron intake, blocking subsequent absorption and increasing gastrointestinal side effects without improving efficacy. 1, 6

Add vitamin C 500 mg with each iron dose to enhance absorption, especially when transferrin saturation is markedly low. 1, 3 If ferrous sulfate is not tolerated, ferrous fumarate or ferrous gluconate provide comparable efficacy. 1, 2

Alternatively, alternate-day dosing of 60–120 mg elemental iron may optimize fractional absorption and reduce side effects in iron-deficient women. 6

Expected Response and Monitoring

• Recheck ferritin and transferrin saturation after 8–10 weeks of oral therapy 3
• Continue oral iron for 3 months after ferritin normalizes to fully replenish iron stores, resulting in a total treatment duration of approximately 6–7 months 1, 3
• Monitor ferritin every 6–12 months in patients with recurrent iron deficiency 3

Investigation of Underlying Cause

The cause of iron deficiency must be identified and treated concurrently with iron supplementation. 2, 7

In Adult Men and Postmenopausal Women

Perform bidirectional endoscopy (upper endoscopy + colonoscopy) to exclude gastrointestinal malignancy, as iron deficiency may be the sole presenting sign. 1, 5 Screen for celiac disease with tissue transglutaminase IgA antibodies (present in 3–5% of cases) and test for Helicobacter pylori. 1, 3

In Premenopausal Women

Assess menstrual blood loss first using pictorial blood loss assessment charts (80% sensitivity and specificity for menorrhagia). 1 Menstrual loss, pregnancy, and breastfeeding account for iron deficiency in 5–10% of menstruating women. 1, 2

Screen for celiac disease with anti-endomysial antibodies and total IgA measurement. 1, 3 Reserve endoscopy for women ≥45 years, those with upper GI symptoms, alarm features, or family history of colorectal cancer. 1

Additional Considerations

• Review medications (NSAIDs, aspirin, proton-pump inhibitors) that contribute to iron loss 1
• Assess dietary iron intake, though borderline deficiency alone does not justify foregoing full investigation 1
• Consider history of gastrointestinal surgery (gastrectomy, gastric bypass) that impairs absorption 1

Indications for Intravenous Iron

Switch to intravenous iron when: 1, 2, 5

• Intolerance to at least two different oral iron formulations
• Ferritin fails to improve after 8–10 weeks of compliant oral therapy
• Active inflammatory bowel disease (hepcidin-mediated absorption blockade)
• Post-bariatric surgery (disrupted duodenal absorption)
• Celiac disease with inadequate response despite strict gluten-free diet
• Chronic kidney disease, heart failure, or cancer (chronic inflammatory conditions)
• Second and third trimesters of pregnancy when oral iron fails

Prefer IV iron formulations that replace iron deficits in 1–2 infusions, such as ferric carboxymaltose (750–1000 mg per 15-minute infusion) or ferric derisomaltose (1000 mg single infusion). 1, 2 All IV iron must be administered in a setting equipped with resuscitation facilities. 1

Special Population Considerations

Pregnancy

Iron deficiency affects up to 84% of pregnant women during the third trimester. 2 Start oral low-dose iron 30 mg/day at the first prenatal visit for prevention, and treat deficiency with 60–120 mg/day elemental iron. 1 IV iron is safe and effective during the second and third trimesters when oral therapy fails. 1, 2

Inflammatory Bowel Disease

In patients with active IBD, use IV iron as first-line therapy because oral iron is poorly absorbed and may exacerbate inflammation. 1, 2 For quiescent disease with mild deficiency, oral iron may be appropriate. 1

Chronic Kidney Disease

In non-dialysis CKD stages 3–5, start iron when ferritin <100 ng/mL and transferrin saturation <20%. 4 Hemodialysis patients require IV iron as the preferred route. 4

Critical Pitfalls to Avoid

• Do not prescribe multiple daily oral doses; this increases side effects without improving efficacy due to hepcidin-mediated absorption blockade 1, 6
• Do not discontinue iron when ferritin normalizes; continue for 3 months to restore stores 1, 3
• Do not overlook vitamin C supplementation when oral iron response is suboptimal 1, 3
• Do not fail to identify and treat the underlying cause while providing supplementation 1, 2
• Do not delay investigation in high-risk patients (age ≥45–50, alarm symptoms, or treatment failure), as malignancy may present solely with iron deficiency 1, 5

Failure to Respond Algorithm

If ferritin does not improve after 8–10 weeks: 1, 3

1. Verify adherence to oral iron therapy
2. Evaluate for ongoing blood loss (repeat endoscopy or video-capsule endoscopy)
3. Consider malabsorption syndromes (celiac disease, IBD, post-bariatric surgery)
4. Check for concurrent vitamin B12 or folate deficiency
5. Switch to intravenous iron if oral therapy failure is confirmed