In a 13‑year‑old female with hemoglobin 17.5 g/dL, hematocrit 52.6 %, RBC count 6.23 ×10⁶/µL, serum iron 103 µg/dL, total iron‑binding capacity 468 µg/dL, transferrin saturation 22 %, red cell distribution width 12.2 %, platelet count 472 ×10³/µL, vitamin B12 282 pg/mL, folate 16.6 ng/mL, and 25‑hydroxy‑vitamin D 12.2 ng/mL, what supplementation regimen is recommended?

Immediate Vitamin D Supplementation Required

This 13-year-old requires urgent vitamin D supplementation for severe deficiency (12.2 ng/mL), with a loading dose followed by maintenance therapy; her iron parameters are normal and do not require supplementation, while her B12 and folate are adequate.

Critical Finding: Severe Vitamin D Deficiency

Her vitamin D level of 12.2 ng/mL represents severe deficiency (below the 10-12 ng/mL threshold that dramatically increases risk for rickets and osteomalacia) 1. This is particularly concerning in a 13-year-old during peak bone development.

Vitamin D Treatment Protocol

Loading Phase:

• Administer 50,000 IU vitamin D2 or D3 once weekly for 8 weeks 2
• Alternative: Weight-adjusted loading doses can be used, though the weekly regimen is well-established

Maintenance Phase:

• After loading: 800-2000 IU daily 1, 2
• Target level: 30-40 ng/mL 2
• Recheck 25(OH)D level at 3 months minimum after starting supplementation 2

Important considerations:

• Vitamin D3 (cholecalciferol) is preferred over D2 if both available, especially for intermittent dosing 2
• Avoid single annual bolus doses (>500,000 IU) which may cause harm 2
• Daily or weekly dosing is safer than large infrequent boluses

Iron Status: No Supplementation Needed

Her iron parameters are normal and do not warrant supplementation:

• Transferrin saturation 22% is above the 20% threshold for iron deficiency 3
• Serum iron 103 µg/dL is normal
• RDW 12.2% is normal (elevated RDW is the earliest marker of iron deficiency) 4

Why Her Labs Look Unusual

Her elevated hemoglobin (17.5 g/dL), hematocrit (52.6%), and RBC count (6.23) suggest:

• Polycythemia (relative or absolute)
• Possible dehydration
• High altitude residence
• Other causes requiring evaluation

Critical pitfall: Do NOT give iron supplementation based on TIBC alone. Her TIBC of 468 µg/dL is elevated, but this is expected when iron stores are normal-to-high and does not indicate deficiency. The transferrin saturation (22%) and normal serum iron confirm adequate iron status 3, 5.

Vitamin B12 and Folate: Adequate

• B12 of 282 pg/mL is low-normal but adequate (typically >200 pg/mL is sufficient)
• Folate 16.6 ng/mL is excellent
• No supplementation needed for either

Monitoring Plan

1. Recheck vitamin D at 3 months after starting supplementation 2
2. Investigate polycythemia - her elevated hemoglobin/hematocrit needs evaluation for secondary causes
3. Consider B12 monitoring if symptoms of deficiency develop, though current level is acceptable

Summary Treatment Plan

Start immediately:

• Vitamin D: 50,000 IU weekly × 8 weeks, then 800-2000 IU daily maintenance

Do NOT supplement:

• Iron (normal status despite elevated TIBC)
• B12 or folate (adequate levels)

Follow-up:

• Vitamin D level in 3 months
• Evaluate cause of polycythemia

The elevated platelet count (472) may be reactive and should normalize with vitamin D repletion, but monitor if it persists.