What is the recommended dose of vitamin D (International Units) for adults?

Recommended Vitamin D Dosing for Adults

The American Heart Association recommends a daily dose of vitamin D3 (cholecalciferol) of 600 IU for adults up to age 70 and 800 IU for adults over 70 years of age, with a safe upper limit of 4,000 IU per day for most adults. 1

Standard Dosing Recommendations

The recommended daily intake of vitamin D varies based on age and risk factors:

• General adult population (up to age 70): 600 IU daily 1
• Adults over 70 years: 800 IU daily 1
• Safe upper limit: 4,000 IU daily for most adults 1

Special Populations Requiring Higher Doses

Certain groups require higher vitamin D supplementation:

• Dark-skinned or veiled individuals: 800 IU/day 1
• Institutionalized individuals: 800 IU/day 1
• Obese patients: May require higher doses (up to 7,000 IU/day) 2
• Patients with malabsorption or liver disease: May require higher doses (up to 7,000 IU/day or 30,000 IU/week) 1, 2
• Multi-morbid patients on multiple medications: May require higher doses due to drug interactions affecting vitamin D metabolism 2

Treatment of Vitamin D Deficiency

When deficiency is identified (serum 25-hydroxyvitamin D levels <20 ng/mL), a more aggressive approach is needed:

• Initial repletion phase: 50,000 IU weekly for 8 weeks (either ergocalciferol/D2 or cholecalciferol/D3) 1, 3
• Maintenance therapy after repletion: 1,000-2,000 IU daily or 50,000 IU monthly 1, 3
• Severe deficiency (<5 ng/mL): May require 50,000 IU weekly for 8-12 weeks 1

Monitoring Recommendations

• Check 25(OH)D levels after 3 months of supplementation 1
• Adjust dosing based on follow-up levels 1
• Goal: Achieve and maintain serum 25(OH)D levels above 30 ng/mL (75 nmol/L) 1

Important Considerations and Pitfalls

• Avoid ultra-high single loading doses (>300,000 IU) as they have not shown benefit and may lead to vitamin D toxicity 1
• Vitamin D toxicity typically occurs at serum levels above 150 ng/mL 1
• Signs of toxicity include hypercalcemia, hypercalciuria, and nephrocalcinosis 1
• BMI affects dosing requirements - higher BMI requires higher doses 4
• Age affects dosing - older adults may need higher doses 4
• Serum albumin affects vitamin D metabolism and dosing requirements 4

Dosing Algorithm

1. For prevention in healthy adults: 600 IU daily (up to age 70) or 800 IU daily (over age 70)
2. For high-risk individuals (obesity, dark skin, institutionalized, etc.): 800-2,000 IU daily
3. For treatment of deficiency:
   • Initial: 50,000 IU weekly for 8 weeks
   • Maintenance: 1,000-2,000 IU daily or 50,000 IU monthly
4. For severe deficiency: 50,000 IU weekly for 8-12 weeks, then maintenance dosing
5. For malabsorption or obesity: Consider higher doses (up to 7,000 IU daily or 30,000 IU weekly)

The differences in recommendations between guidelines reflect different goals and interpretations of the evidence, with the US Endocrine Society generally recommending higher doses (1,500-2,000 IU daily for adults) to maintain 25(OH)D above 30 ng/mL, while the Institute of Medicine recommends lower doses (600-800 IU) to maintain levels above 20 ng/mL 5.