What is the recommended regimen for vitamin D replacement in individuals with vitamin D deficiency?

Vitamin D Replacement for Deficiency

For vitamin D deficiency (<20 ng/mL), start with a loading dose of 50,000 IU vitamin D2 once weekly for 8 weeks, followed by a maintenance dose of 800-2000 IU daily. 1

Initial Treatment Based on Deficiency Severity

• For standard vitamin D deficiency (<20 ng/mL), begin with 50,000 IU vitamin D2 (ergocalciferol) once weekly for 8 weeks 1
• For severe deficiency (<10-12 ng/mL), use the same regimen of 50,000 IU weekly but extend to 8-12 weeks 1
• When rapid correction is needed (e.g., for acutely ill patients or after fragility fracture), loading doses are necessary, though many regimens exist from single doses up to 600,000 IU to multiple daily/weekly doses of 50,000 IU 2
• Each 1,000 IU of vitamin D supplementation typically increases serum 25(OH)D levels by approximately 10 ng/mL, though individual responses vary significantly 1

Maintenance Phase

• After completing the loading dose regimen, transition to a maintenance dose of 800-2000 IU daily 1
• Vitamin D3 (cholecalciferol) is preferred over vitamin D2 (ergocalciferol) for maintenance therapy, especially when using intermittent dosing regimens 1
• For patients with malabsorption or obesity, higher maintenance doses may be required (2000-4000 IU daily) 1, 3
• For patients preferring less frequent dosing, 50,000 IU monthly or 100,000 IU every 3 months are effective maintenance options 1

Special Populations

• For obese patients, patients with liver disease, or those with malabsorption syndromes, consider higher daily doses of 7,000 IU/day or intermittent doses of 30,000 IU/week as prophylactic or maintenance doses 3
• For treatment of deficiency in these high-risk groups, consider 30,000 IU twice weekly or 50,000 IU weekly for a 6-8 week period 3
• For elderly patients (≥65 years), institutionalized individuals, and those with dark skin or limited sun exposure, supplementation with 800 IU/day can be initiated without baseline testing 1

Monitoring Response to Treatment

• Measure 25(OH)D levels after 3-6 months of supplementation to ensure adequate dosing and allow serum levels to reach plateau 2, 1
• Target 25(OH)D level should be at least 30 ng/mL (75 nmol/L) for optimal health benefits 1, 4
• The upper safety limit for 25(OH)D is considered to be 100 ng/mL (250 nmol/L) 1

Important Caveats

• Bolus doses are useful in many circumstances, but maintenance doses are still needed, and longer dosing intervals than a week may be inefficient or even harmful 2
• Single ultra-high loading doses (e.g., 540,000 IU) without maintenance dosing have been shown to be inefficient 2
• Vitamin D toxicity is rare but can occur with prolonged high doses (typically >10,000 IU daily), causing hypercalcemia, hypercalciuria, dizziness, and renal failure 2, 1
• Avoid single large doses of 300,000-500,000 IU 5
• Calcium intake should be assessed alongside vitamin D supplementation, with recommended daily intake of 1000-1500 mg 1
• Mineral oil interferes with the absorption of vitamin D, and thiazide diuretics may cause hypercalcemia in patients taking vitamin D supplements 6

Enteral and Parenteral Nutrition Considerations

• Enteral nutrition should provide at least 1000 IU (25 μg) per day of vitamin D in 1500 kcal 2
• Parenteral nutrition should provide at least 200 IU (5 μg) of vitamin D per day 2