High Dose Vitamin D Prescription for Severe Deficiency
For patients with confirmed severe vitamin D deficiency, the recommended prescription is 50,000 IU of vitamin D weekly for 8-12 weeks, followed by maintenance therapy of 800-2,000 IU daily. 1, 2
Initial Treatment Phase
- For severe vitamin D deficiency (<10-12 ng/mL), prescribe 50,000 IU cholecalciferol (vitamin D3) weekly for 8-12 weeks 3, 1, 2
- Cholecalciferol (vitamin D3) is preferred over ergocalciferol (vitamin D2) due to higher bioefficacy and better maintenance of serum levels 1, 2
- The FDA-approved formulation is available as 50,000 IU softgel capsules, with directions to take one capsule weekly with food 4
- This loading dose approach is necessary because standard daily doses would take many weeks to normalize severely low vitamin D levels 3, 1
Maintenance Phase
- After completing the loading dose regimen, transition to a maintenance dose of 800-2,000 IU daily 3, 1, 2
- For convenience, monthly dosing of 50,000 IU can be used as maintenance therapy (equivalent to approximately 1,600 IU daily) 3, 1
- Ensure adequate calcium intake (1,000-1,500 mg daily) alongside vitamin D supplementation 1, 2
Monitoring Response
- Check vitamin D levels (25-hydroxyvitamin D) after 3-6 months of supplementation to ensure adequate response 3, 1
- Target serum 25(OH)D level should be at least 30 ng/mL for optimal bone health and anti-fracture efficacy 3, 1
- Individual response to vitamin D supplementation is variable due to genetic factors, requiring monitoring to ensure adequate dosing 3, 1
Special Considerations
- For patients with malabsorption syndromes (e.g., celiac disease), higher doses may be required or alternative routes of administration (IM) may be considered 3, 1
- For obese patients, higher doses may be needed due to sequestration of vitamin D in adipose tissue - consider 7,000 IU daily or 30,000 IU weekly as maintenance 5
- For elderly patients (≥65 years), a minimum of 800 IU daily is recommended even without baseline measurement 3, 1
Safety Considerations
- Daily doses up to 4,000 IU are generally considered safe for adults 2
- Most international authorities consider vitamin D intake of 2,000 IU daily as absolutely safe 3
- Vitamin D toxicity is rare but can occur with prolonged high doses (typically >10,000 IU daily) 3
- Single very large doses (>300,000 IU) should be avoided as they may be inefficient or potentially harmful 3, 1
- Hypercalcemia caused by excess vitamin D has been observed only if daily intake was >100,000 IU or if the 25(OH)D level exceeded 100 ng/mL 3
Alternative Dosing Regimens
- For patients requiring rapid correction, a 10-day course of 50,000 IU daily (total 500,000 IU) has been shown to effectively normalize vitamin D levels 6
- A weight-based dosing formula can be used: dose (IU) = 40 × (75 - current serum 25-OHD) × body weight (kg) 7
- For patients with persistent deficiency despite standard therapy, consider evaluating for malabsorption or medication interactions 1