What is the recommended dosage of vitamin D (International Units) for adults and children?

Vitamin D Dosage Recommendations

Standard Daily Dosing for Adults

For general adult supplementation, 600-800 IU daily is recommended for maintenance, while adults at risk for deficiency should receive 1500-4000 IU daily. 1

Age-Based Recommendations

• Adults 19-70 years: 600 IU daily meets the needs of 97.5% of the population for basic bone health 1, 2
• Adults over 70 years: 800 IU daily is recommended due to decreased skin synthesis with aging 1, 2
• Elderly patients (≥65 years): Higher doses of 800-1,000 IU daily reduce fall and fracture risk more effectively 1, 3

Higher Dosing for At-Risk Populations

• Dark-skinned or veiled individuals with limited sun exposure: 800 IU/day without baseline testing 1
• Institutionalized subjects: 800 IU/day without baseline testing 1
• Patients with obesity, malabsorption, or chronic illness: 1500-4000 IU daily 1
• Post-bariatric surgery patients: At least 2,000-3,000 IU daily, with intramuscular administration preferred when available 1, 3
• Patients on chronic glucocorticoids (≥2.5 mg/day for >3 months): 600-800 IU daily minimum, targeting serum 25(OH)D levels of 30-50 ng/mL 1

Standard Daily Dosing for Children

Children require age-appropriate vitamin D dosing, with 400-1000 IU daily for infants and 600-1000 IU daily for children over 1 year. 2

Age-Based Pediatric Recommendations

• Infants under 1 year: 400-1000 IU per day 2
• Children 1 year and older: 600-1000 IU per day 2

Treatment of Vitamin D Deficiency

For documented vitamin D deficiency (25(OH)D <20 ng/mL), initiate 50,000 IU weekly for 8-12 weeks, followed by maintenance therapy of 800-2,000 IU daily. 1, 3

Loading Phase Protocol

• Standard loading regimen: 50,000 IU of vitamin D3 (cholecalciferol) once weekly for 8-12 weeks 1, 3
• Severe deficiency (<10 ng/mL): 50,000 IU weekly for 12 weeks, then monthly maintenance 3
• Rapid correction when clinically indicated: 6,000 IU daily for 4-12 weeks before transitioning to maintenance 4
• Alternative for severe deficiency: Loading doses up to 600,000 IU administered over several weeks (not as single dose) 1, 5

Maintenance Phase After Correction

• Standard maintenance: 800-2,000 IU daily or 50,000 IU monthly (equivalent to ~1,600 IU daily) 1, 3
• Higher maintenance for recurrent deficiency: 4,000-5,000 IU daily for 2 months to achieve blood levels of 40-60 ng/mL 1

Vitamin D3 vs D2 Selection

Cholecalciferol (D3) is strongly preferred over ergocalciferol (D2) because it maintains serum levels longer and has superior bioavailability, particularly for intermittent dosing regimens. 1, 3

Target Serum Levels and Monitoring

The optimal target range for serum 25(OH)D is 30-80 ng/mL, with anti-fracture efficacy starting at 30 ng/mL and anti-fall efficacy beginning at 24 ng/mL. 1, 3

Monitoring Protocol

• Wait at least 3 months after starting supplementation before measuring 25(OH)D levels to assess response 1, 3
• For intermittent dosing (weekly or monthly): Measure just prior to the next scheduled dose 1, 3
• Follow-up after deficiency treatment: Recheck levels after 3-6 months to ensure adequate response 1, 3

Dosing Rule of Thumb

• 1,000 IU vitamin D daily increases serum 25(OH)D by approximately 10 ng/mL, though individual responses vary due to genetic differences in vitamin D metabolism 1, 6

Safety Considerations

Daily doses up to 4,000 IU are considered absolutely safe for adults, with the Endocrine Society recommending an upper limit of 10,000 IU for at-risk patients. 1

Safety Parameters

• Most international authorities consider 2,000 IU daily as absolutely safe 1
• Doses up to 10,000 IU per day supplemented over several months have not led to adverse events in studies 1
• Upper safety limit for serum 25(OH)D: 100 ng/mL 1, 3
• Hypercalcemia due to vitamin D toxicity generally occurs only when daily intake exceeds 100,000 IU or when 25(OH)D levels exceed 100 ng/mL 1, 6

Critical Pitfalls to Avoid

Single annual mega-doses (≥500,000 IU) should be avoided as they have been associated with adverse outcomes including increased falls and fractures. 1

Common Mistakes

• Avoid bolus doses with intervals longer than weekly, as daily or weekly dosing shows superior protective effects, especially for preventing respiratory infections 1
• Do not use active vitamin D analogs (calcitriol, alfacalcidol, doxercalciferol, paricalcitol) to treat nutritional vitamin D deficiency 3
• Ensure adequate calcium intake (1,000-1,500 mg daily) alongside vitamin D supplementation, as vitamin D enhances calcium absorption 1, 3
• Monitor serum and urinary calcium during high-dose therapy, as hypercalcemia can occur even without hypervitaminosis D 1

Special Administration Considerations

Dosing Frequency Options

Daily dosing is physiologically preferred, but weekly or monthly regimens are acceptable alternatives for improving compliance. 1

• Daily dosing: Most physiologic approach 1
• Weekly dosing: 50,000 IU once weekly has been shown to be effective 1
• Monthly dosing: 50,000-60,000 IU monthly has similar effects on 25(OH)D concentration as equivalent daily doses 1, 6

Intramuscular Administration

For patients with malabsorption syndromes who fail oral supplementation, intramuscular vitamin D3 50,000 IU results in significantly higher 25(OH)D levels and lower rates of persistent deficiency. 3

• Indications for IM administration: Post-bariatric surgery (especially malabsorptive procedures), inflammatory bowel disease, pancreatic insufficiency, short-bowel syndrome 3
• Limitation: IM vitamin D preparations are not universally available and may be contraindicated in patients on anticoagulation 3
• Alternative for malabsorption when IM unavailable: Substantially higher oral doses (4,000-5,000 IU daily) or oral calcifediol [25(OH)D] due to higher intestinal absorption 3