What is the recommended frequency for ergocalciferol (Vitamin D2) supplementation in an older adult with vitamin D deficiency and a history of osteoporosis, should it be weekly or every two weeks?

Ergocalciferol Should Be Given Weekly, Not Every Two Weeks

For an older adult with vitamin D deficiency and osteoporosis, ergocalciferol 50,000 IU should be administered once weekly for 8-12 weeks, not every two weeks. 1, 2

Why Weekly Dosing Is the Standard

The weekly regimen is the evidence-based standard across all major guidelines for treating vitamin D deficiency:

• The loading phase requires 50,000 IU ergocalciferol once weekly for 8-12 weeks to effectively correct deficiency and achieve target 25(OH)D levels of at least 30 ng/mL, which is critical for anti-fracture efficacy in patients with osteoporosis 1, 2

• For severe deficiency (levels <10 ng/mL), the 12-week duration is specifically recommended, while 8 weeks may suffice for moderate deficiency (10-20 ng/mL) 1

• This weekly regimen delivers approximately 600,000 IU total over the treatment period, which research demonstrates is the minimum cumulative dose needed to achieve vitamin D sufficiency in the majority of patients 3

Evidence Against Every-Two-Week Dosing

Every-two-week dosing is not supported by clinical evidence and would be inadequate:

• Spreading the same total dose over a longer interval (every 2 weeks) would extend treatment to 16-24 weeks, delaying achievement of therapeutic levels and leaving the patient at continued risk for falls and fractures 1

• Studies show that regimens containing at least 600,000 IU of ergocalciferol achieved sufficiency in only 64% of cases when given over approximately 60 days—extending this timeline further would likely reduce efficacy 3

• For osteoporosis patients specifically, achieving 25(OH)D levels ≥30 ng/mL rapidly is essential, as fracture prevention requires these levels and delays in treatment increase fracture risk 1

Special Considerations for This Patient

Given the combination of advanced age and osteoporosis:

• After completing the 8-12 week loading phase, transition to maintenance therapy of 50,000 IU monthly (equivalent to approximately 1,600 IU daily) or 800-2,000 IU daily 1, 2

• Ensure adequate calcium intake of 1,000-1,500 mg daily from diet plus supplements if needed, as calcium is essential for the clinical response to vitamin D therapy and fracture prevention 1, 2

• Calcium supplements should be taken in divided doses of no more than 600 mg at once for optimal absorption 1

Monitoring Protocol

• Recheck 25(OH)D levels 3 months after completing the loading phase to confirm adequate response, with a target of at least 30 ng/mL for anti-fracture efficacy 1, 2

• If levels remain below 30 ng/mL despite adherence, consider increasing maintenance dosing or investigating malabsorption 1

• For elderly patients with osteoporosis, higher maintenance doses of 1,000-2,000 IU daily are often more effective at reducing fall and fracture risk than the standard 800 IU daily 1

Critical Pitfall to Avoid

• Never use active vitamin D analogs (calcitriol, alfacalcidol, doxercalciferol, paricalcitol) to treat nutritional vitamin D deficiency, as they bypass normal regulatory mechanisms and carry higher risk of hypercalcemia without correcting 25(OH)D levels 1

Preference for Cholecalciferol Over Ergocalciferol

While ergocalciferol is effective, cholecalciferol (vitamin D3) is strongly preferred over ergocalciferol (vitamin D2) because it maintains serum levels longer, has superior bioavailability, and is particularly advantageous for intermittent dosing regimens 1, 2