What is the recommended weekly dose of vitamin D (cholecalciferol) for a general adult population?

Weekly Vitamin D Dosing

For vitamin D deficiency treatment, the standard weekly dose is 50,000 IU of vitamin D (cholecalciferol or ergocalciferol) taken once weekly for 8-12 weeks, followed by maintenance therapy. 1

Treatment Protocol Based on Vitamin D Status

For Documented Deficiency (<20 ng/mL)

• Administer 50,000 IU once weekly for 8-12 weeks as the loading phase. 1 This is the most widely recommended regimen across major guidelines including recommendations from the American Journal of Kidney Diseases and National Comprehensive Cancer Network. 1
• For severe deficiency (<10 ng/mL), especially with symptoms or high fracture risk, extend the loading phase to 12 weeks. 1
• Cholecalciferol (vitamin D3) is strongly preferred over ergocalciferol (vitamin D2) because it maintains serum levels longer and has superior bioavailability, particularly important for weekly dosing intervals. 1, 2

After Loading Phase: Maintenance Options

• Transition to 50,000 IU once monthly (equivalent to approximately 1,600 IU daily) to maintain optimal levels. 1
• Alternatively, use daily maintenance of 2,000 IU or higher depending on individual factors. 1
• Target serum 25(OH)D level of at least 30 ng/mL for optimal anti-fracture efficacy. 1

Alternative Weekly Dosing Strategies

For Insufficiency (20-30 ng/mL) Without Loading Phase

• Consider 30,000 IU weekly as a maintenance dose for patients at high risk of deficiency, including those with obesity, liver disease, or malabsorption syndromes. 3 This dose is effective for prolonged use without monitoring.
• For treatment of possible deficiency in high-risk groups, 30,000 IU twice weekly for 6-8 weeks can be used. 3

Weekly Equivalent of Daily Dosing

• A weekly dose of 250 μg (10,000 IU) is equivalent to approximately 50 μg (2,000 IU) daily and is equally effective at increasing serum 25(OH)D levels without risk of hypercalciuria. 4 This is suitable for prevention rather than treatment of deficiency.

Critical Monitoring and Safety Considerations

When to Recheck Levels

• Measure 25(OH)D levels 3 months after initiating weekly supplementation to allow vitamin D stores to plateau and accurately reflect treatment response. 1 If using intermittent dosing, measure just prior to the next scheduled dose. 1

Essential Co-Interventions

• Ensure adequate calcium intake of 1,000-1,500 mg daily from diet plus supplements if needed, as calcium is necessary for vitamin D therapy to work properly. 1, 5
• Take vitamin D with the largest, fattiest meal of the day to maximize absorption, as it is fat-soluble. 1

Safety Parameters

• Avoid single ultra-high doses exceeding 300,000 IU as they may be inefficient or potentially harmful, particularly for fall and fracture prevention. 1
• The 50,000 IU weekly regimen is well-established as safe with no significant adverse events in clinical trials. 1
• Daily doses up to 4,000 IU (or weekly equivalent of 28,000 IU) are considered completely safe for long-term use. 1, 5
• Upper safety limit for serum 25(OH)D is 100 ng/mL. 1, 2

Special Population Considerations

Malabsorption Syndromes

• For patients with malabsorption (post-bariatric surgery, inflammatory bowel disease, pancreatic insufficiency), consider 50,000 IU 2-3 times weekly or even daily in severe cases. 1 Intramuscular administration may be necessary if oral supplementation fails. 1

Chronic Kidney Disease (Stages 3-4)

• Use standard nutritional vitamin D (cholecalciferol or ergocalciferol) with the same 50,000 IU weekly regimen for 8-12 weeks. 1 Never use active vitamin D analogs (calcitriol, alfacalcidol) to treat nutritional deficiency, as they bypass normal regulatory mechanisms and carry higher hypercalcemia risk. 1

Elderly Patients (≥65 years)

• After loading phase, maintain with at least 800 IU daily (or 5,600 IU weekly equivalent) to reduce fall and fracture risk. 1

Common Pitfalls to Avoid

• Do not use weekly doses of 1,250 μg (50,000 IU) as long-term maintenance without monitoring, as this may increase risk of hypercalciuria, particularly in patients with BMI >26 kg/m². 4
• Verify patient adherence before increasing doses for inadequate response, as poor compliance is a common reason for treatment failure. 1
• Do not measure vitamin D levels too early (before 3 months), as this will not reflect steady-state levels and may lead to inappropriate dose adjustments. 1
• Ensure total 25(OH)D (D2 + D3) is measured if patient is on ergocalciferol supplements. 1