What is the recommended treatment for vitamin D (Vit D) deficiency?

Vitamin D Deficiency: Evaluation and Treatment

Definition and Diagnostic Thresholds

Vitamin D deficiency is defined as serum 25-hydroxyvitamin D [25(OH)D] below 20 ng/mL and requires prompt treatment. 1, 2

• Insufficiency is defined as 20-30 ng/mL 1, 3
• Optimal levels for health benefits, particularly anti-fracture efficacy, are ≥30 ng/mL 1, 2, 4
• Severe deficiency (<10-12 ng/mL) significantly increases risk for osteomalacia and rickets 1
• Upper safety limit is 100 ng/mL—levels above this increase toxicity risk 1, 2

Treatment Protocol

Loading Phase for Deficiency (<20 ng/mL)

For documented vitamin D deficiency, prescribe ergocalciferol (vitamin D2) 50,000 IU once weekly for 8-12 weeks. 1, 2, 4

• This regimen delivers a cumulative dose of 400,000-600,000 IU over the treatment period 1
• For severe deficiency (<10 ng/mL) with symptoms or high fracture risk, extend to 12 weeks 1
• Avoid single ultra-high doses (>300,000 IU) as they may be inefficient or harmful 1, 3

Maintenance Phase

After completing the loading dose, transition to cholecalciferol (vitamin D3) 2,000 IU daily for long-term maintenance. 1, 2, 4

• Vitamin D3 is strongly preferred over D2 for maintenance because it maintains serum levels longer and has superior bioavailability 1, 2, 4
• Alternative maintenance: 50,000 IU monthly (equivalent to ~1,600 IU daily) 1
• For elderly patients (≥65 years), minimum 800 IU daily, though 700-1,000 IU daily is more effective for fall and fracture prevention 1

Essential Co-Interventions

Ensure adequate calcium intake of 1,000-1,500 mg daily from diet plus supplements if needed. 1, 2, 4

• Calcium supplements should be taken in divided doses of no more than 600 mg at once for optimal absorption 1
• Adequate calcium is necessary for clinical response to vitamin D therapy 5

Monitoring Protocol

Recheck 25(OH)D levels 3 months after starting treatment to confirm adequate response. 1, 2, 4

• Target level is ≥30 ng/mL for anti-fracture efficacy 1, 2
• Anti-fall efficacy begins at 24 ng/mL 1
• If using intermittent dosing (weekly or monthly), measure just prior to the next scheduled dose 1
• If levels remain below 30 ng/mL despite adherence, increase maintenance dose by 1,000-2,000 IU daily 1

Special Populations

Malabsorption Syndromes

For patients with malabsorption (post-bariatric surgery, inflammatory bowel disease, short-bowel syndrome), intramuscular vitamin D 50,000 IU is preferred. 1

• IM administration results in significantly higher 25(OH)D levels and lower rates of persistent deficiency compared to oral supplementation 1
• When IM is unavailable or contraindicated (anticoagulation, infection risk), use substantially higher oral doses: 4,000-5,000 IU daily 1
• Post-bariatric surgery patients require at least 2,000 IU daily to prevent recurrent deficiency 1

Chronic Kidney Disease

For CKD patients with GFR 20-60 mL/min/1.73m², treat with standard ergocalciferol or cholecalciferol. 1

• CKD is a major risk factor for vitamin D deficiency due to reduced sun exposure, dietary restrictions, and increased urinary losses 1
• Do not use active vitamin D analogs (calcitriol, alfacalcidol, doxercalciferol, paricalcitol) to treat nutritional vitamin D deficiency—these do not correct 25(OH)D levels 1, 5

Elderly and High-Risk Groups

Dark-skinned, veiled, or institutionalized individuals should receive 800 IU daily without requiring baseline measurement. 1

• Elderly patients have decreased skin synthesis and require higher maintenance doses 1

Safety Considerations

Daily doses up to 4,000 IU are generally safe for adults. 1, 5, 3

• Some evidence supports up to 10,000 IU daily for several months without adverse effects 1, 6
• Toxicity typically occurs only with prolonged high doses (>10,000 IU daily) or serum levels >100 ng/mL 1
• Symptoms of toxicity include hypercalcemia, hyperphosphatemia, suppressed PTH, and hypercalciuria 1
• Monitor serum calcium in patients receiving high therapeutic doses 5

Critical Pitfalls to Avoid

• Never use active vitamin D analogs for nutritional deficiency—reserve these for advanced CKD with impaired 1α-hydroxylase activity 1, 5
• Avoid single very large doses (>300,000 IU)—they may increase fall and fracture risk 1, 3
• Do not recommend sun exposure for deficiency prevention due to increased skin cancer risk 1
• Mineral oil interferes with absorption of fat-soluble vitamins including vitamin D 5
• Thiazide diuretics in hypoparathyroid patients on ergocalciferol may cause hypercalcemia 5

Expected Response

Using the rule of thumb: 1,000 IU vitamin D daily increases serum 25(OH)D by approximately 10 ng/mL, though individual responses vary. 1

• Individual response is variable due to genetic differences in vitamin D metabolism 1
• Body composition affects requirements: high body fat sequesters vitamin D, high muscle mass increases retention 1
• Skin pigmentation and genetic polymorphisms also impact bioavailability 1

Practical Dosing Summary

For insufficiency (20-30 ng/mL): Add 1,000 IU daily and recheck in 3 months 1

For deficiency (<20 ng/mL): 50,000 IU weekly × 8-12 weeks, then 2,000 IU daily maintenance 1, 2, 4

For severe deficiency (<10 ng/mL): 50,000 IU weekly × 12 weeks, then 50,000 IU monthly or 2,000 IU daily 1

For prevention in elderly (≥65 years): 800-1,000 IU daily 1