How long after Monofer (ferric derisomaltose) infusion should iron levels be re-tested?

Timing for Iron Level Re-Testing After Monofer (Ferric Derisomaltose) Infusion

Iron levels should be re-tested 3 months after Monofer infusion, as early re-evaluation within 4 weeks should be avoided due to artificially elevated ferritin levels that cannot be used as an accurate indicator of iron status during this time. 1

Optimal Timing for Re-Testing

• Iron parameters should not be evaluated within 4 weeks of intravenous iron administration, as serum levels of ferritin increase markedly following administration and cannot be utilized as a reliable marker of iron status during this period 1
• Following iron replacement, iron status should be re-evaluated in 3 months, with further iron repletion provided as needed 1
• Laboratory evaluation following IV iron should include complete blood count (CBC) and iron parameters (ferritin, percent transferrin saturation) 4 to 8 weeks after the last infusion 1

Rationale for Waiting Period

• Ferritin levels increase significantly after IV iron administration, creating falsely elevated readings that do not accurately reflect true iron stores if measured too soon 1
• The 3-month interval allows sufficient time for the body to process and distribute the administered iron, providing a more accurate assessment of the patient's iron status 1
• Hemoglobin concentrations typically increase within 1-2 weeks of treatment and should increase by 1-2 g/dL within 4-8 weeks of therapy 1

Monitoring Parameters

• Key parameters to measure at follow-up include hemoglobin, hematocrit, ferritin, and transferrin saturation (TSAT) 1
• TSAT is calculated by dividing the serum iron concentration by the total iron-binding capacity and multiplying by 100 1
• For accurate assessment of iron parameters after intravenous infusion of larger doses (≥1000 mg), an interval of at least 2 weeks should occur, though 3 months is optimal 1

Special Considerations

• If there is no response or hemoglobin levels decrease after treatment, further investigation for other underlying causes should be considered, particularly occult blood loss 1
• After correction of iron deficiency, consider re-evaluation of iron parameters 1-2 times per year as part of routine follow-up 1
• Iron status should be re-evaluated if patients remain symptomatic despite receiving optimal background medications, or if hemoglobin levels decrease 1

MRI Considerations

• If MRI imaging is needed, the required time interval between the last IV iron infusion and MRI for Monofer (iron isomaltoside/ferric derisomaltose) is 1 month to avoid magnetic interference 1
• This differs from other iron preparations such as iron sucrose and ferric carboxymaltose (1 week), high-molecular-weight iron dextran (3 months), or ferumoxytol (6 months) 1

Long-Term Monitoring

• Following attainment of target hemoglobin/hematocrit levels, TSAT and serum ferritin should be determined at least once every 3 months in patients on regular iron therapy 1
• For patients with chronic conditions requiring ongoing iron monitoring, consider evaluating iron status as part of routine practice 1-2 times per year 1