What is the best course of treatment for a patient with iron deficiency anemia, vitamin D deficiency, and mildly impaired kidney function?

Management of Iron Deficiency, Vitamin D Deficiency, and Mild CKD

This patient requires oral iron supplementation, vitamin D3 supplementation (50,000 IU monthly for 6 months), and monitoring for potential need of erythropoietin therapy if anemia persists after iron repletion.

Iron Deficiency Management

Diagnosis Confirmation

This patient has absolute iron deficiency based on CKD-specific criteria: 1

• Iron saturation 6% (TSAT ≤20% defines iron deficiency in CKD)
• Ferritin 22 ng/mL (≤100 μg/L defines absolute iron deficiency in predialysis CKD patients)
• With eGFR 80 mL/min/1.73m², this represents CKD stage 2

Treatment Approach

Oral iron is the preferred first-line therapy for this predialysis CKD patient: 1

• The British Society of Gastroenterology guidelines recommend oral iron replacement for predialysis CKD patients as initial therapy 1
• Intravenous iron should be reserved for patients who fail oral therapy, cannot tolerate it, or have progressed to dialysis 1

Monitoring strategy: 1

• Recheck hemoglobin and iron studies (ferritin, TSAT) every 3 months 1
• Complete blood count with red cell indices and reticulocyte count should be obtained 1
• If anemia persists after 4 weeks of adequate iron supplementation, evaluate for other contributing factors including vitamin B12, folate, and copper deficiency 1

Erythropoietin Consideration

ESA therapy should be considered if anemia persists despite iron repletion: 1

• The KDIGO guidelines recommend ESA therapy for CKD patients who remain anemic despite appropriate iron therapy 1
• Treatment should be initiated if hemoglobin remains <10.0 g/dL after correcting iron deficiency 1
• Weekly monitoring of hemoglobin is required during ESA dose titration 1

Vitamin D Deficiency Management

Diagnosis

Vitamin D level of 18.9 ng/mL represents deficiency (normal ≥30 ng/mL): 1, 2

• Vitamin D deficiency is independently associated with decreased kidney function 2
• In CKD patients with eGFR <30 mL/min/1.73m², vitamin D deficiency is associated with abnormal mineral and bone disorder markers 2

Treatment Protocol

Ergocalciferol (vitamin D2) 50,000 IU orally monthly for 6 months: 1

• This is the recommended regimen from the Renal Physicians Association guidelines for CKD patients with vitamin D insufficiency (25(OH)D <30 ng/mL) 1
• Alternative: cholecalciferol (vitamin D3) can be used with similar dosing 1

Monitoring requirements: 1

• Measure serum calcium and phosphorus every 3 months 1
• Monitor 25(OH) vitamin D levels after completing the 6-month course 1
• Watch for hypercalcemia, which can occur with vitamin D supplementation 3

Important Caveats

Vitamin D toxicity considerations: 3

• Hypervitaminosis D manifests as hypercalcemia with anorexia, nausea, weakness, and polyuria 3
• Treatment effects can persist 2+ months after cessation 3
• Thiazide diuretics can cause hypercalcemia when combined with vitamin D therapy 3

Kidney Function Monitoring

Current Status Assessment

With creatinine 1.04 mg/dL and eGFR 80 mL/min/1.73m², this represents CKD stage 2: 1

• Anemia monitoring should occur every 3 months at this stage 1
• Blood pressure should be checked at every clinic visit (at least every 3 months) 1

Mineral and Bone Disorder Screening

Calcium, phosphorus, and PTH monitoring: 1

• Not yet required at eGFR 80 (threshold is GFR <30 mL/min/1.73m²) 1
• However, given vitamin D deficiency, baseline calcium and phosphorus should be checked before starting supplementation 1

Alkaline Phosphatase Consideration

Alkaline phosphatase of 118 U/L (assuming normal range ~30-120 U/L) is at the upper limit of normal: 1

• This may reflect early bone turnover abnormalities related to vitamin D deficiency 2
• Does not require specific intervention at this time but warrants monitoring 1
• If it rises above normal range, consider checking intact PTH even though eGFR >30 1

Follow-up Timeline

4-week reassessment: 1

• Evaluate response to iron therapy by checking reticulocyte count 1
• If no improvement, investigate other causes of anemia 1

3-month reassessment: 1

• Recheck hemoglobin, iron studies (ferritin, TSAT), calcium, phosphorus 1
• Assess vitamin D level after completing supplementation course 1
• Consider ESA therapy if anemia persists despite corrected iron stores 1

Common pitfall to avoid: Do not use general population cutoffs for iron deficiency in CKD patients—ferritin <100 μg/L (not <12 ng/mL) and TSAT ≤20% define absolute iron deficiency in predialysis CKD. 1