What is the recommended use and dosage of Vitamin D2 (ergocalciferol) for treating vitamin D deficiency?

Vitamin D2 (Ergocalciferol) Treatment for Vitamin D Deficiency

For treating vitamin D deficiency, ergocalciferol (vitamin D2) should be dosed according to severity: 50,000 IU weekly for 8-12 weeks for severe deficiency (<5 ng/mL), 8,000 IU daily for 4 weeks then 4,000 IU daily for 2 months for mild deficiency (5-15 ng/mL), and 4,000 IU daily for 12 weeks or 50,000 IU every other week for 12 weeks for insufficiency (16-30 ng/mL). 1

Dosing Recommendations Based on Deficiency Severity

Severe Vitamin D Deficiency (<5 ng/mL)

• Initial treatment: 50,000 IU weekly for 8-12 weeks 1
• Alternative regimen: 8,000 IU daily for 4 weeks, then 4,000 IU daily for 2 months 2, 1

Mild Vitamin D Deficiency (5-15 ng/mL)

• Initial treatment: 8,000 IU daily for 4 weeks, then 4,000 IU daily for 2 months 2, 1
• Alternative regimen: 50,000 IU weekly for 4 weeks, then 50,000 IU twice monthly for 2 months 2

Vitamin D Insufficiency (16-30 ng/mL)

• Treatment: 4,000 IU daily for 12 weeks 2, 1
• Alternative regimen: 50,000 IU every other week for 12 weeks 1
• Another option: 2,000 IU daily or 50,000 IU monthly 2

Maintenance Therapy

After achieving vitamin D repletion (serum 25(OH)D ≥30 ng/mL), maintenance therapy should be initiated:

• Recommended maintenance: 2,000 IU daily or 50,000 IU every 4 weeks 1
• For long-term supplementation: 800-2,000 IU daily 1, 3

Monitoring Recommendations

• Recheck 25(OH)D levels 3 months after initiating treatment to assess efficacy 1
• Monitor serum calcium and phosphorus levels regularly to detect potential toxicity 1
• Annual monitoring of 25(OH)D levels is recommended, preferably at the end of darker months 1

Comparative Efficacy

It's important to note that cholecalciferol (vitamin D3) appears to have higher bioefficacy than ergocalciferol (vitamin D2), although long-term comparative trials in humans are lacking 2, 1. The American Journal of Kidney Diseases and European cystic fibrosis guidelines recommend cholecalciferol over ergocalciferol for patients with chronic kidney disease due to this higher bioefficacy 1.

Safety Considerations

Vitamin D2 has a high therapeutic index and is generally safe even at high doses 4. A case report documented a patient who received 150,000 IU of ergocalciferol daily for 28 years without toxicity 5. However, hypercalcemia is the primary sign of excessive dosing, and vitamin D toxicity can occur with daily doses >50,000 IU that produce 25(OH)D levels >150 ng/mL 1.

Special Populations

• Elderly patients: May require 800-1,000 IU daily 1
• Patients with CKD: Higher doses may be required; dosing should be adjusted based on severity of deficiency 2, 1
• Obese patients or those with malabsorption: May require higher doses, such as 50,000 IU weekly 1

Treatment Efficacy

Research has shown that regimens containing at least 600,000 IU of ergocalciferol appear to be most effective in achieving vitamin D sufficiency 6. A study comparing different high-dose regimens found that a 10-day course of vitamin D3 (50,000 IU daily for 10 days) was more effective than a single mega-dose of 600,000 IU vitamin D2 7.

Practical Considerations

Ergocalciferol is available in various formulations, including oral solution drops containing 8,000 IU per mL 8, making it suitable for patients who have difficulty swallowing pills or require precise dosing.