What does a serum iron level of 7.9 umol/l indicate in a patient with Chronic Kidney Disease (CKD)?

Serum Iron of 7.9 umol/L in CKD Indicates Severe Iron Deficiency

A serum iron level of 7.9 umol/L (approximately 44 mcg/dL) in a CKD patient represents severe iron deficiency that requires immediate iron supplementation to prevent worsening anemia and its associated morbidity and mortality.

Understanding the Severity

• Normal serum iron ranges from 10-30 umol/L (60-170 mcg/dL), making 7.9 umol/L markedly low 1, 2
• This level indicates absolute iron deficiency where iron stores are severely depleted and iron delivery to erythroid marrow is critically impaired 3
• In CKD patients, absolute iron deficiency is defined by transferrin saturation (TSAT) ≤20% and serum ferritin <100 ng/mL in non-dialysis/peritoneal dialysis patients or <200 ng/mL in hemodialysis patients 1

Clinical Implications and Required Actions

You must check TSAT and ferritin immediately to fully characterize the iron deficiency and guide treatment intensity 3:

• If TSAT <20% and ferritin <100 ng/mL (or <200 ng/mL if on hemodialysis), this confirms absolute iron deficiency requiring aggressive iron repletion 3, 1
• Iron supplementation must be initiated before or concurrent with any erythropoiesis-stimulating agent (ESA) therapy, as ESAs will be ineffective without adequate iron stores 3, 4
• Failure to correct iron deficiency leads to ESA hyporesponsiveness, unnecessarily high ESA doses, increased costs, and potential adverse cardiovascular effects 4

Treatment Algorithm Based on CKD Stage

For Hemodialysis Patients (CKD Stage 5D):

• Intravenous iron is mandatory - oral iron cannot maintain adequate stores due to ongoing dialyzer blood losses and impaired absorption 3, 1, 5
• Administer 100-125 mg IV iron weekly for 8-10 doses (total 1.0 g) to rapidly replete stores 3, 4
• Target ferritin >200 ng/mL and TSAT >20% before initiating ESA therapy 4, 1
• Continue maintenance IV iron (25-125 mg weekly) to sustain these targets 3

For Non-Dialysis and Peritoneal Dialysis Patients (CKD Stages 3-5):

• Trial oral iron first: at least 200 mg elemental iron daily for adults 3, 1
• If after 3 months ferritin remains <100 ng/mL or TSAT <20%, switch to IV iron 4, 1
• For IV iron: administer 500-1,000 mg iron dextran as single infusion (after 25 mg test dose) or 100-125 mg weekly for 8-10 weeks 3, 4
• Target ferritin >100 ng/mL and TSAT >20% 4, 1

Monitoring Strategy

• During iron repletion: Check TSAT and ferritin monthly until targets achieved 3, 4
• After achieving targets: Monitor every 3 months 3
• IV iron doses ≤125 mg weekly do not require interruption for accurate iron parameter measurement 3

Critical Pitfalls to Avoid

• Never start ESA therapy without first ensuring adequate iron stores - this is the most common cause of treatment failure 4
• Do not confuse this with functional iron deficiency (adequate ferritin but low TSAT), which represents different pathophysiology 3
• Recognize that anemia itself (Hgb <9 g/dL) increases infection risk and mortality more than iron deficiency treatment 3
• The risk of undertreating iron deficiency far exceeds theoretical risks of iron supplementation in this setting 3, 6

Upper Safety Limits

• Continue iron supplementation until ferritin reaches 500 ng/mL (non-dialysis) or 800 ng/mL (hemodialysis) 6, 4
• Patients are unlikely to respond further once TSAT reaches 50% or ferritin reaches 800 ng/mL 3, 4