What is the recommended follow-up for ferritin (Ferritin) and transferrin saturation (TSAT) levels in patients with iron deficiency anemia after initiating iron therapy?

Monitoring Ferritin and TSAT After Iron Therapy

Check hemoglobin at 4 weeks after starting oral iron, then recheck complete iron studies (ferritin and TSAT) at 3 months to assess iron store replenishment. 1

Oral Iron Monitoring Schedule

Initial Response Check (4 Weeks)

• Measure hemoglobin only at 4 weeks to determine if treatment is working 1, 2
• Expect hemoglobin to rise 1-2 g/dL within 4-8 weeks of starting therapy 1
• If no response by 2-4 weeks, consider switching to intravenous iron 2

Complete Iron Studies (3 Months)

• Recheck ferritin, TSAT, and hemoglobin at 3 months to assess whether iron stores are adequately replenished 1
• Continue oral iron for a full 3 months after hemoglobin normalizes to ensure adequate marrow iron store repletion 1
• Stopping iron prematurely results in recurrence of iron deficiency in >50% of patients within 1 year 1

Long-Term Surveillance

• After achieving normal hemoglobin and iron stores, monitor hemoglobin and red cell indices every 3 months for the first year, then annually 1
• For patients with chronic conditions requiring ongoing iron, check iron status 1-2 times per year 1

Intravenous Iron Monitoring Schedule

Critical Timing Considerations

• Do NOT check ferritin within 4 weeks of IV iron administration - ferritin becomes falsely elevated and unreliable during this period 1
• For IV iron doses ≥1000 mg, wait 4-8 weeks before rechecking iron parameters for accurate assessment 1
• For smaller IV iron doses (100-500 mg), wait at least 1-2 weeks before checking iron studies 1
• Hemoglobin can be checked at 4 weeks after IV iron to assess response 1

Special Population: Chronic Kidney Disease Patients on ESAs

Standard Monitoring Frequency

• Monitor ferritin and TSAT at least every 3 months in all CKD patients receiving erythropoietin-stimulating agent (ESA) therapy 3, 4
• This 3-month interval serves as the foundation for decisions to start or continue iron supplementation 4

When to Monitor More Frequently

• Monthly monitoring when initiating ESA therapy during the initial treatment phase 4
• When increasing ESA dose to assess iron adequacy 3, 4
• After blood loss events to detect iron depletion 3
• When monitoring response after completing a course of IV iron 3

Target Iron Parameters in CKD

• Maintain TSAT >20% and ferritin >100 ng/mL in non-dialysis and peritoneal dialysis CKD patients 3, 4
• Maintain TSAT >20% and ferritin >200 ng/mL in hemodialysis patients 4
• Avoid IV iron if ferritin >500 ng/mL due to insufficient evidence of benefit 4

Special Population: Inflammatory Bowel Disease

• Monitor for recurrent iron deficiency every 3 months for at least a year after correction, then between 6-12 months thereafter 1
• Re-treat with IV iron when serum ferritin drops below 100 μg/L or hemoglobin falls below 12 g/dL (women) or 13 g/dL (men) 1

Critical Pitfalls to Avoid

• Checking ferritin too soon after IV iron (within 4 weeks) yields falsely elevated readings that do not reflect true iron stores 1
• Stopping oral iron when hemoglobin normalizes without continuing for an additional 3 months results in inadequate iron store repletion and early recurrence 1
• Monitoring TSAT and ferritin at least every 3 months allows detection of functional iron deficiency before it impairs ESA response and prevents iron overload 4