What is the recommended dosage of vitamin D (Vit D) for treating a confirmed vitamin D deficiency?

Vitamin D Dosage for Confirmed Vitamin D Deficiency

For confirmed vitamin D deficiency, the recommended treatment is 50,000 IU of vitamin D2 (ergocalciferol) once weekly for 8-12 weeks, followed by a maintenance dose of 1,000-2,000 IU daily. 1, 2

Initial Treatment Phase

Dosing Strategy Based on Deficiency Severity:

• Severe deficiency (<20 ng/mL or <50 nmol/L):

  • 50,000 IU of ergocalciferol weekly for 8-12 weeks 1, 2
  • This loading dose approach effectively replenishes vitamin D stores

• Mild to moderate deficiency (20-30 ng/mL or 50-75 nmol/L):

  • 50,000 IU of ergocalciferol weekly for 8 weeks 1
  • Alternative: 2,000 IU of cholecalciferol (vitamin D3) daily for 12 weeks 3

Monitoring During Initial Phase:

• Recheck vitamin D levels after 3 months of supplementation 1
• Check calcium and phosphorus levels at baseline and after 4 weeks of supplementation 1
• Discontinue therapy if serum corrected calcium exceeds 10.2 mg/dL or phosphorus exceeds 4.6 mg/dL 1

Maintenance Phase

After achieving normal vitamin D levels (>30 ng/mL or >75 nmol/L), transition to maintenance therapy:

• Standard maintenance dose: 1,000-2,000 IU daily 1, 2
• Alternative maintenance approach: 50,000 IU monthly 3

Special Populations Requiring Higher Doses

Certain populations may require higher doses due to increased risk of deficiency:

• Obesity: 7,000 IU daily or 30,000 IU weekly 4
• Malabsorption syndromes: 7,000 IU daily or 30,000-50,000 IU weekly 4
• Liver disease: 7,000 IU daily or 30,000 IU weekly 4
• Elderly (≥65 years): At least 800-1,000 IU daily 1, 2
• Chronic kidney disease: Specialized approach needed 1

Important Considerations and Cautions

• The therapeutic window for vitamin D is relatively narrow 5
• Avoid single large doses of 300,000-500,000 IU as they may increase risk of falls and fractures 1, 6
• Daily dosing is generally preferred over intermittent high-dose supplementation 1
• Each 1,000 IU of daily vitamin D supplementation typically increases serum 25(OH)D by approximately 10 ng/mL 1
• The upper safety limit for daily intake is generally 4,000 IU for adults, though the Endocrine Society suggests up to 10,000 IU daily may be safe for those at risk for deficiency 1, 6

Calcium Supplementation

• Consider concurrent calcium supplementation (1,200 mg daily from all sources) for optimal bone health 1
• This is particularly important for patients with osteoporosis or at risk for fractures

Follow-up Monitoring

• Recheck vitamin D levels 3 months after starting supplementation 1
• If levels remain insufficient after 3 months:
  • Verify compliance with the prescribed regimen
  • Consider increasing the maintenance dose 1
• For patients on long-term supplementation with doses >1,000 IU daily, check vitamin D levels every two years 7