Ergocalciferol (Vitamin D2) Dosing for Vitamin D Deficiency/Insufficiency
For patients with vitamin D deficiency or insufficiency, ergocalciferol (Vitamin D2) should be dosed based on the severity of deficiency, with 50,000 IU weekly for 8-12 weeks being the standard approach for most patients, followed by maintenance therapy. 1
Dosing Protocol Based on Severity
Severe Vitamin D Deficiency (25(OH)D < 5 ng/mL)
- Initial therapy: 50,000 IU ergocalciferol weekly for 12 weeks 1
- Maintenance: 50,000 IU monthly after repletion 1
- Alternative: 8,000 IU/day orally for 4 weeks, then 4,000 IU/day for 2 months 1
Mild Vitamin D Deficiency (25(OH)D 5-15 ng/mL)
- Initial therapy: 50,000 IU ergocalciferol weekly for 8 weeks 1
- Maintenance: 50,000 IU monthly after repletion 1
- Alternative: 4,000 IU/day orally for 12 weeks or 50,000 IU every other week for 12 weeks 1
Vitamin D Insufficiency (25(OH)D 16-30 ng/mL)
- Initial therapy: 50,000 IU ergocalciferol every 2 weeks for 12 weeks 2
- Maintenance: 2,000 IU daily or 50,000 IU every 4 weeks 1
Monitoring and Target Levels
- Check 25(OH)D levels after 3 months of supplementation 2
- Target 25(OH)D level: ≥30 ng/mL 1, 2
- Monitor serum calcium in patients at risk for hypercalcemia 2
- After achieving repletion (25(OH)D ≥30 ng/mL), maintain with 200-1,000 IU daily 1
Special Populations
Chronic Kidney Disease (CKD)
- For CKD patients, dosing follows the same protocol but requires more careful monitoring 1
- Higher doses may be more effective in CKD: A study showed that double the K/DOQI recommended dose significantly increased 25(OH)D levels (from 20.99 to 33.41 ng/mL) and decreased PTH levels (from 90.75 to 76.40 pg/mL) 3
- Important: Do not use calcitriol, alfacalcidol, or other synthetic active vitamin D analogs to treat 25(OH)D deficiency 1
Obese Patients and Malabsorption
- May require 2-3 times the standard dose 2
- Consider 50,000-100,000 IU/week for better repletion in these patients 4
Safety Considerations
- Vitamin D toxicity is rare but can occur with daily doses >50,000 IU that produce 25(OH)D levels >150 ng/mL 2
- Upper safety limit for 25(OH)D is generally considered 100 ng/mL 2
- Ergocalciferol has been administered at doses of 10,000 IU daily in CKD patients for over a year without evidence of toxicity 1
- Case reports document patients receiving much higher doses (e.g., 150,000 IU daily for 28 years) without toxicity, though this is not recommended 5
Practical Administration Tips
- Take ergocalciferol with food to reduce GI symptoms 2
- Ensure adequate calcium intake of 1,000-1,200 mg daily from all sources 2
- If GI symptoms occur, consider splitting the dose or reducing frequency (e.g., 50,000 IU every 2 weeks instead of weekly) 2
Efficacy Considerations
- Higher doses (100,000 IU/week) achieve optimal 25(OH)D levels more effectively than standard doses (40,000 IU/week), particularly in severe deficiency 6
- For long-term treatment, dosage should be adjusted by monitoring 25(OH)D levels periodically 7
Remember that hypercalcemia is the primary sign of excessive dosing, and development of this condition would indicate a need to reduce or temporarily discontinue therapy 1.