What is the recommended weekly dose of vitamin D (Vitamin D) for individuals with insufficient levels?

Weekly Vitamin D Dosing for Insufficiency

For adults with vitamin D insufficiency (20-30 ng/mL), the standard weekly dose is 50,000 IU of vitamin D once weekly for 8-12 weeks, followed by maintenance therapy of 50,000 IU monthly or 1,500-2,000 IU daily. 1, 2

Treatment Protocol Based on Vitamin D Status

For Vitamin D Insufficiency (20-30 ng/mL)

• Loading phase: 50,000 IU of vitamin D2 (ergocalciferol) or D3 (cholecalciferol) once weekly for 8-12 weeks 1, 2
• Maintenance phase: Transition to either 50,000 IU monthly (equivalent to ~1,600 IU daily) or 1,500-2,000 IU daily 1, 2
• Target level: Achieve serum 25(OH)D ≥30 ng/mL for optimal anti-fracture efficacy 1, 2

For Vitamin D Deficiency (<20 ng/mL)

• Same loading regimen: 50,000 IU weekly for 8-12 weeks 1, 2
• Severe deficiency (<10-12 ng/mL): May extend to 12 weeks, then continue with 50,000 IU monthly 1, 2

Vitamin D3 vs D2 Selection

• Strongly prefer cholecalciferol (D3) over ergocalciferol (D2) because D3 maintains serum levels longer and has superior bioavailability, particularly important for weekly or monthly dosing intervals 1, 2

Essential Co-Interventions

• Calcium intake: Ensure 1,000-1,500 mg daily from diet plus supplements if needed 1, 2
• Calcium dosing strategy: Take supplements in divided doses of no more than 600 mg at once for optimal absorption 1, 2
• Weight-bearing exercise: At least 30 minutes, 3 days per week 1

Monitoring Protocol

• Recheck 25(OH)D levels after 3-6 months of treatment to confirm adequate response 1, 2
• Timing of measurement: If using weekly or monthly dosing, measure just prior to the next scheduled dose 1, 2
• Dose adjustment: If levels remain <30 ng/mL after 3 months, increase maintenance dose by 1,000-2,000 IU daily or equivalent 1

Special Populations Requiring Modified Approach

Elderly Patients (≥65 years)

• Minimum daily dose: 800 IU daily even without baseline measurement 1, 2
• Optimal dose for fall/fracture prevention: 700-1,000 IU daily shows superior efficacy 1, 2

Chronic Kidney Disease (CKD stages 3-5)

• Use standard nutritional vitamin D (ergocalciferol or cholecalciferol), not active vitamin D analogs 3, 1, 2
• For GFR 20-60 mL/min/1.73m²: Standard replacement regimen applies 1, 2
• Monitor for hypercalcemia more closely in this population 2

Malabsorption Syndromes

• Intramuscular (IM) vitamin D3 50,000 IU is preferred over oral supplementation for post-bariatric surgery, inflammatory bowel disease, or short-bowel syndrome 1
• If IM unavailable: Use substantially higher oral doses (4,000-5,000 IU daily for 2 months, then at least 2,000 IU daily maintenance) 1
• Alternative: Oral calcifediol [25(OH)D] has higher intestinal absorption rates when IM is contraindicated 1

Critical Pitfalls to Avoid

• Never use active vitamin D analogs (calcitriol, alfacalcidol, doxercalciferol, paricalcitol) to treat nutritional vitamin D deficiency—these do not correct 25(OH)D levels 3, 1, 2
• Avoid single ultra-high loading doses (>300,000 IU) as they may be inefficient or harmful, particularly for fall and fracture prevention 1, 2
• Do not supplement patients with normal vitamin D levels (≥30 ng/mL)—benefits are only seen in those with documented deficiency 1
• Correct vitamin D deficiency before initiating bisphosphonates to prevent hypocalcemia 2

Safety Considerations

• Daily doses up to 4,000 IU are generally safe for adults, with some evidence supporting up to 10,000 IU daily for several months 1, 2
• Upper safety limit: Serum 25(OH)D should not exceed 100 ng/mL 1, 2
• Toxicity manifestations: Hypercalcemia, hyperphosphatemia, suppressed PTH, and hypercalciuria—rare with recommended dosing 1
• Weekly 50,000 IU dosing for 8-12 weeks has been well-established as safe with no significant adverse events in clinical trials 1

Expected Response to Treatment

• Rule of thumb: 1,000 IU daily increases serum 25(OH)D by approximately 10 ng/mL, though individual responses vary due to genetic differences in vitamin D metabolism 1
• Anti-fall efficacy: Begins at achieved levels ≥24 ng/mL 1, 2
• Anti-fracture efficacy: Requires achieved levels ≥30 ng/mL 1, 2

Practical Dosing Equivalents

• 50,000 IU monthly = approximately 1,600 IU daily 3, 1
• 50,000 IU every 2 weeks = approximately 3,500 IU daily 3
• 50,000 IU weekly = approximately 7,000 IU daily 3