Therapeutic Dosing of Vitamin D3 (Cholecalciferol)
The recommended therapeutic dose of vitamin D3 is 600 IU daily for adults aged 19-70 years and 800 IU daily for adults over 70 years, with optimal serum levels targeted between 30-40 ng/mL (75-100 nmol/L). 1
Standard Dosing Guidelines
General adult population:
- Ages 19-70: 600 IU daily
- Ages >70: 800 IU daily 1
Target serum levels:
- Minimum threshold: 20 ng/mL (50 nmol/L)
- Optimal range: 30-40 ng/mL (75-100 nmol/L)
- Upper safety limit: 100 ng/mL (250 nmol/L) 1
Special Population Dosing
Higher doses are required for specific populations:
Dark-skinned or veiled individuals, adults ≥65 years, institutionalized individuals: 800 IU/day 1
Bariatric surgery patients: 3,000 IU daily, titrated up to 6,000 IU daily as needed 2, 1
Patients with severe malabsorption: 50,000 IU 1-3 times weekly to daily 1
Patients with obesity: 2-3 times higher doses (up to 7,000 IU daily) 1
Patients with liver disease: Higher doses due to impaired hepatic 25-hydroxylation 1
Dosing Based on Deficiency Severity
| Vitamin D Level | Supplementation Strategy |
|---|---|
| 15-20 ng/mL | 800-1,000 IU/day |
| 5-15 ng/mL | 50,000 IU weekly for 4-8 weeks, then maintenance |
| <5 ng/mL | Individualized treatment under close monitoring |
| [1] |
High-Dose Supplementation Safety
Research shows that long-term supplementation with vitamin D3 in doses ranging from 5,000 to 50,000 IU/day appears to be safe in most adults 3. However, the American Heart Association recommends adhering to established upper intake limits of 4,000 IU/day for adults 1.
The FDA-approved vitamin D3 product label indicates that 50,000 IU doses are typically administered weekly rather than daily for therapeutic purposes 4.
Monitoring Recommendations
- Check 25(OH)D levels 3-4 months after initiating therapy
- Annual monitoring for maintenance therapy
- Recheck in 3-6 months after dose adjustments
- Monitor serum calcium and phosphorus with high-dose supplementation 1
Important Considerations
- Vitamin D has a half-life of 2 weeks to 3 months and is stored in adipose tissue and liver, so daily replacement may not be necessary 2
- Adequate calcium intake (1000-1500 mg daily) is necessary alongside vitamin D supplementation for optimal bone health 1
- Vitamin D toxicity is rare and typically occurs with much higher doses (>10,000 IU daily for extended periods), with serum 25-hydroxyvitamin D levels >150 ng/mL indicating toxicity 1
- Recent research suggests that 2,000 IU/day is effective for maintaining vitamin D levels within the recommended range during winter months, while 4,000 IU/day was more effective for maintaining levels above 100 nmol/l 5
Cautions
- Patients with hypercalcemia, malabsorption syndrome, abnormal sensitivity to vitamin D, and hypervitaminosis D should avoid supplementation 4
- Patients taking thiazide diuretics may be at greater risk of toxicity 4
- Not recommended for children, pregnant or lactating women, or individuals with liver disease without medical supervision 4