Vitamin D3 Dosing for Adults Over 65
Adults over 65 should take 800-1000 IU of vitamin D3 daily, combined with 1000-1200 mg of calcium (preferably from dietary sources first, with supplements to fill the gap). 1, 2
Evidence-Based Dosing Recommendations
The most robust evidence supports higher-dose vitamin D supplementation in this age group:
- High-dose vitamin D (≥800 IU daily) reduces hip fracture risk by 30% and nonvertebral fracture risk by 14% in adults 65 years and older 1, 2
- Lower doses (400 IU or less) have shown no significant benefit for fracture prevention 3
- Most clinical trials demonstrating efficacy used at least 800 IU daily 3
Target Serum Levels
- Aim for a 25(OH)D level of at least 30 ng/mL (75 nmol/L) for optimal bone health 1, 2
- Levels below 20 ng/mL are considered deficient and increase risk of secondary hyperparathyroidism and bone loss 2, 4
- Each 40 IU increment of vitamin D3 increases 25(OH)D by approximately 0.4 ng/mL 1
Calcium Considerations
Total daily calcium intake should be 1000-1200 mg from all sources (diet plus supplements): 1, 2
- Prioritize dietary calcium sources first - they carry lower cardiovascular and kidney stone risk than supplements 2
- If supplements are needed, divide doses to no more than 500-600 mg at a time for optimal absorption 2
- Calculate current dietary intake before prescribing supplements to avoid over-supplementation 2
Important Caveats and Safety
Potential harms to consider:
- Calcium supplementation increases kidney stone risk (1 case per 273 women supplemented over 7 years) 3, 2
- Avoid very high intermittent doses - single large doses (300,000-500,000 IU annually) may actually increase fall and fracture risk 2
- Doses below 400 IU daily are ineffective for fracture prevention 2
Special Populations Requiring This Dosing
This 800-1000 IU daily recommendation is particularly important for: 2
- Institutionalized elderly
- Dark-skinned or veiled individuals with limited sun exposure
- Patients on glucocorticoid therapy (≥2.5 mg/day for >3 months)
- Those with documented osteoporosis or history of fractures
Monitoring Strategy
- Check baseline 25(OH)D level, especially if risk factors for deficiency exist 1
- Recheck vitamin D levels after 3 months of supplementation to ensure adequacy 2
- Consider periodic assessment every 1-2 years thereafter 1
- Monitor serum calcium if history of kidney stones or hypercalcemia 2
Formulation Preference
Vitamin D3 (cholecalciferol) is preferred over vitamin D2 (ergocalciferol), particularly for intermittent dosing regimens 2, 5
Adjunctive Measures
Vitamin D and calcium supplementation should be combined with: 1
- Regular weight-bearing exercise (30 minutes at least 3 days per week)
- Smoking cessation
- Limiting alcohol intake
- Balance and muscle strengthening exercises to prevent falls