What form of vitamin D (Vit D) is recommended for treating vitamin D deficiency?

Vitamin D Supplementation for Deficiency

For treating vitamin D deficiency, vitamin D3 (cholecalciferol) is recommended as the preferred form over vitamin D2 (ergocalciferol), especially when using intermittent dosing regimens. 1

Diagnosis of Vitamin D Deficiency

• Vitamin D deficiency is defined as serum 25(OH)D levels:
  • Deficiency: <20 ng/mL (<50 nmol/L) 2
  • Insufficiency: 20-30 ng/mL (50-75 nmol/L) 2
  • Target level for optimal health: >30 ng/mL (>75 nmol/L) 1

Treatment Algorithm for Vitamin D Deficiency

Initial Loading Dose (Correction Phase)

1. For most adults with vitamin D deficiency:

   • Vitamin D3 (cholecalciferol): 50,000 IU weekly for 8 weeks 2
   • Alternative: Weight-based dosing using formula: Dose (IU) = 40 × (75 - current serum 25(OH)D) × body weight 3

2. For high-risk patients (obesity, malabsorption, liver disease):

   • Higher doses may be required: 30,000 IU twice weekly or 50,000 IU weekly for 6-8 weeks 4

Maintenance Phase

1. Standard maintenance:

   • Vitamin D3: 800-1,000 IU daily 2
   • For higher-risk individuals: 2,000 IU daily 5

2. Intermittent dosing option:

   • 50,000 IU monthly after normalization of levels 1

Special Considerations

Route of Administration

• Oral administration is preferred and most common
• IM route available but generally reserved for severe malabsorption cases

Monitoring

• Measure serum 25(OH)D levels after at least 3 months of supplementation 1
• Use an assay that measures both 25(OH)D2 and 25(OH)D3 1
• Follow-up testing is essential due to variable individual responses to supplementation

Population-Specific Recommendations

• Elderly (>65 years): 800 IU daily without baseline testing 1
• Dark-skinned or veiled individuals: 800 IU daily without baseline testing 1
• Institutionalized individuals: 800 IU daily without baseline testing 1
• Chronic kidney disease patients: Ergocalciferol may be preferred, especially in advanced CKD 1

Safety Considerations

• Ensure adequate dietary calcium intake for optimal response to vitamin D therapy 6
• Upper safety limit for 25(OH)D is 100 ng/mL 1
• Vitamin D3 is a high-potency supplement; do not exceed recommended dosage 7
• Use caution in patients with liver disease or those taking thiazide diuretics 7
• Monitor for hypercalcemia in high-dose regimens, though this is rare at recommended doses

Common Pitfalls to Avoid

1. Inadequate loading dose: Many clinicians prescribe maintenance doses without proper loading, resulting in prolonged deficiency
2. Failure to monitor: Not checking 25(OH)D levels after 3-6 months to ensure adequate response
3. Ignoring maintenance therapy: Stopping supplementation after correction phase, leading to recurrence
4. Not accounting for individual factors: Obesity, malabsorption, and certain medications require higher doses
5. Using calcitriol for deficiency: Active vitamin D analogs should not be used to treat nutritional vitamin D deficiency 1

The evidence strongly supports vitamin D3 over vitamin D2 for intermittent dosing regimens, as vitamin D3 maintains serum 25(OH)D concentrations for a longer period 1. While both forms can be effective with daily dosing, the practical advantages of vitamin D3 make it the preferred choice for most patients.