Vitamin D3 Injection Regimen for Severe Vitamin D Deficiency
For patients with severe vitamin D deficiency (<5 ng/mL), the recommended treatment is 50,000 IU of vitamin D3 weekly for 8-12 weeks, followed by maintenance therapy of 1,000-2,000 IU daily. 1
Treatment Algorithm Based on Severity
The treatment approach should be tailored according to the patient's vitamin D level:
Severe deficiency (<5 ng/mL):
- Initial therapy: 50,000 IU weekly for 8-12 weeks
- Followed by maintenance: 1,000-2,000 IU daily
- Consider individualized treatment under close monitoring for extremely low levels 1
Moderate deficiency (5-15 ng/mL):
- 50,000 IU weekly for 4-8 weeks
- Followed by maintenance therapy 1
Mild deficiency (15-20 ng/mL):
- 800-1,000 IU daily 1
Special Population Considerations
Higher doses may be required for certain populations:
- Obesity: 2-3 times higher doses (up to 7,000 IU daily) due to sequestration in adipose tissue 1
- Malabsorption syndromes: Higher doses or weekly regimens 1
- Liver disease: Higher doses due to impaired hepatic 25-hydroxylation 1
- Chronic kidney disease: Specialized approaches with monitoring of calcium and phosphorus levels 1
Administration and Monitoring
- Check vitamin D levels after 3 months of therapy to ensure target levels have been reached 1
- Target level should be >32 ng/mL, although some experts recommend 40-50 ng/mL 2
- Monitor serum calcium and phosphorus if using higher doses or in patients with conditions affecting calcium metabolism 1
- Vitamin D deficiency should be corrected prior to initiation of bisphosphonate therapy to avoid hypocalcemia 2
Safety Considerations
- Daily vitamin D doses up to 4,000 IU are considered safe, as this is below the threshold where toxicity risk increases 1
- Long-term supplementation with vitamin D3 in doses ranging from 5,000 to 50,000 IU/day appears to be safe in monitored settings 3
- Vitamin D toxicity typically occurs at serum levels above 150 ng/mL, which is far higher than levels achieved with standard supplementation 1
- Discontinue therapy if serum corrected total calcium exceeds 10.2 mg/dL 1
Important Caveats
- Oral supplementation is generally preferred over injections for most patients
- Injectable forms may be considered for patients with severe malabsorption or poor adherence
- Vitamin D2 (ergocalciferol) or vitamin D3 (cholecalciferol) can be used, but D3 is more bioavailable 2
- Avoid very high yearly loading doses (500,000 IU vitamin D3 each year) as they may be associated with increased risk of fractures and falls 2
- Doses >4,000 IU/day have been associated with more falls and fractures in some populations 4
By following this regimen and monitoring approach, most patients with severe vitamin D deficiency should achieve adequate vitamin D levels and avoid potential complications of deficiency.