What is the recommended dose for treating vitamin D deficiency?

Treatment of Vitamin D Deficiency

For documented vitamin D deficiency (25(OH)D <20 ng/mL), initiate 50,000 IU of vitamin D3 (cholecalciferol) once weekly for 8-12 weeks, followed by maintenance therapy of 800-2,000 IU daily to achieve and maintain target levels of at least 30 ng/mL. 1, 2

Initial Loading Phase

Vitamin D3 (cholecalciferol) is strongly preferred over vitamin D2 (ergocalciferol) because it maintains serum levels longer and has superior bioavailability, particularly for intermittent dosing regimens. 1, 2

The standard loading regimen consists of:

• 50,000 IU once weekly for 8-12 weeks for patients with deficiency (<20 ng/mL) 1, 2, 3
• For severe deficiency (<10 ng/mL), extend the loading phase to 12 weeks 2
• This cumulative dose of 400,000-600,000 IU over 8-12 weeks is necessary to replenish vitamin D stores 1, 4

As a rule of thumb, 1,000 IU daily increases serum 25(OH)D by approximately 10 ng/mL, though individual responses vary due to genetic differences in vitamin D metabolism. 1, 5

Maintenance Phase

After completing the loading phase and achieving target levels:

• Standard maintenance: 800-2,000 IU daily 1, 2, 3, 6
• Alternative intermittent regimen: 50,000 IU monthly (equivalent to approximately 1,600 IU daily) 2
• For elderly patients (≥65 years): minimum 800 IU daily, though 700-1,000 IU daily provides better anti-fall and anti-fracture efficacy 1, 2

Target Serum Levels

The optimal target range is 30-80 ng/mL, with specific thresholds for clinical benefits: 1, 5

• Anti-fall efficacy begins at 25(OH)D ≥24 ng/mL 2
• Anti-fracture efficacy requires ≥30 ng/mL 1, 2
• Upper safety limit is 100 ng/mL 1, 2, 5

Special Populations Requiring Higher Doses

Obesity, Malabsorption, or Multi-Morbidity

• Treatment doses: 6,000-10,000 IU daily for 4-12 weeks, then maintenance of 3,000-6,000 IU daily 1, 7
• Alternative: 30,000 IU twice weekly or 50,000 IU weekly for 6-8 weeks 8
• Post-bariatric surgery patients need at least 2,000-3,000 IU daily for maintenance 1

Malabsorption Syndromes

Intramuscular vitamin D3 50,000 IU is the preferred route for patients with documented malabsorption (inflammatory bowel disease, short-bowel syndrome, post-bariatric surgery) who fail oral supplementation, as it results in significantly higher 25(OH)D levels and lower rates of persistent deficiency. 2

When IM is unavailable or contraindicated:

• Use substantially higher oral doses: 4,000-5,000 IU daily for 2 months 1
• Consider oral calcifediol [25(OH)D] as an alternative due to higher intestinal absorption 2

Chronic Kidney Disease (CKD)

For CKD stages 3-4 (GFR 20-60 mL/min/1.73m²):

• Use standard nutritional vitamin D replacement with ergocalciferol or cholecalciferol 2
• Do not use active vitamin D analogs (calcitriol, alfacalcidol, doxercalciferol, paricalcitol) to treat nutritional vitamin D deficiency 2

Essential Co-Interventions

Ensure adequate calcium intake of 1,000-1,500 mg daily from diet plus supplements, as vitamin D enhances calcium absorption and adequate dietary calcium is necessary for clinical response. 1, 2

• Take calcium supplements in divided doses of no more than 600 mg at once for optimal absorption 2

Monitoring Protocol

• Recheck 25(OH)D levels 3-6 months after starting supplementation to assess response and adjust dosing 1, 2, 5, 7
• For intermittent dosing (weekly or monthly), measure levels just prior to the next scheduled dose 2
• Individual response varies due to genetic differences in vitamin D metabolism, making monitoring essential 2

Critical Pitfalls to Avoid

Do not use single annual mega-doses (≥500,000 IU), as they have been associated with adverse outcomes including increased falls and fractures. 1, 4

Avoid single very large doses (>300,000 IU) as they may be inefficient or potentially harmful. 2

Daily or weekly dosing is physiologically preferable to monthly bolus doses for routine supplementation, as bolus doses with longer intervals may be inefficient or harmful. 1

Safety Considerations

• Daily doses up to 4,000 IU are generally considered safe for adults 1, 2, 6
• Some evidence supports up to 10,000 IU daily for several months without adverse effects 1
• Toxicity typically occurs only with daily intake exceeding 100,000 IU or serum levels >100 ng/mL 1, 5
• Hypercalcemia due to vitamin D toxicity is rare with appropriate dosing 1

Prevention Dosing (Not Deficiency)

For at-risk populations without documented deficiency:

• Dark-skinned or veiled individuals with limited sun exposure: 800 IU daily 1, 5
• Institutionalized individuals: 800 IU daily 1
• Adults at risk for deficiency: 1,500-4,000 IU daily 1, 6