What is the recommended replacement regimen for vitamin D deficiency?

Vitamin D Deficiency Replacement Regimen

For vitamin D deficiency, the recommended replacement regimen is 50,000 IU weekly for 4-8 weeks for levels of 5-15 ng/mL, followed by maintenance therapy of 800-1,000 IU daily. 1

Replacement Regimen Based on Deficiency Severity

Treatment should be tailored according to the severity of vitamin D deficiency:

1. Mild Insufficiency (15-20 ng/mL)

   • 800-1,000 IU daily 1
   • Monitor levels after 3-4 months of therapy

2. Moderate Deficiency (5-15 ng/mL)

   • 50,000 IU weekly for 4-8 weeks 1, 2
   • Then transition to maintenance dose of 800-1,000 IU daily
   • Recheck levels 3-4 months after initiating therapy

3. Severe Deficiency (<5 ng/mL)

   • Requires individualized treatment under close monitoring 1
   • A cumulative dose of at least 600,000 IU administered over several weeks appears necessary to replenish vitamin D stores 3
   • Single large doses of 300,000-500,000 IU should be avoided due to risk of toxicity 3

Special Population Considerations

Higher doses are required for certain populations:

• Obesity: 2-3 times higher doses (up to 7,000 IU daily) 1, 4
• Dark-skinned or veiled individuals: 800 IU daily 1
• Institutionalized individuals: 800 IU daily 1
• Adults ≥65 years: 800 IU daily 1
• Malabsorption syndromes: Higher doses or weekly regimens; minimum 2,000 IU daily for bariatric surgery patients 1, 4
• Liver disease: Higher doses due to impaired hepatic 25-hydroxylation 1, 4

Dosing Formula for Precision

For more precise dosing, the following equation can help determine the required dose:

Dose (IU) = 40 × (75 - current serum 25-OHD level in nmol/L) × body weight in kg 5

Alternatively, for ambulatory patients: Dose (IU/day) = [(8.52 - Desired change in 25-OHD) + (0.074 × Age) - (0.20 × BMI) + (1.74 × Albumin) - (0.62 × Starting 25-OHD)]/(-0.002) 6

Monitoring and Safety

• Recheck vitamin D levels 3-4 months after initiating therapy 1
• Safe upper limit for vitamin D supplementation is 4,000 IU daily for adults 1, 3
• Monitor serum calcium and phosphorus during supplementation, especially with high doses 1, 7
• Ensure adequate calcium intake (1000-1500 mg daily) alongside vitamin D supplementation 1

Important Cautions

• Vitamin D dosage must be readjusted once clinical improvement occurs 7
• In vitamin D resistant rickets, the therapeutic window is narrow 7
• Evaluate all sources of vitamin D (fortified foods, supplements, prescription) 7
• Vitamin D toxicity typically occurs with doses >10,000 IU daily for extended periods 1
• Mineral oil interferes with vitamin D absorption 7
• Thiazide diuretics may cause hypercalcemia in patients on vitamin D therapy 7

Maintenance Therapy

After correcting deficiency, maintenance therapy should be:

• 800-1,000 IU daily for most adults 1, 2
• 600-800 IU daily for adults aged 19-70 years 1
• 800 IU daily for adults over 70 years 1
• At least 2,000 IU daily for patients with risk factors for deficiency 3, 4