What is the recommended dose and administration of vitamin D (Vit D) injections for patients with severe vitamin D deficiency?

Vitamin D Injection Dosing for Severe Vitamin D Deficiency

For patients with severe vitamin D deficiency (<12.5 ng/mL), intramuscular vitamin D (ergocalciferol) should be administered at 50,000 IU weekly for 8 weeks, followed by maintenance therapy, with dose adjustments based on body weight and monitoring of calcium and phosphorus levels. 1

Dosing Recommendations Based on Deficiency Severity

Severe Deficiency (<12.5 ng/mL)

• Initial treatment options:
  • Oral loading dose: 50,000 IU weekly for 8 weeks (total 400,000 IU) 1, 2
  • Intramuscular injection: 600,000 IU as a single dose (for patients with malabsorption or compliance issues) 3
• Monitoring: Check calcium and phosphorus at 1 month, then check 25(OH)D levels after 3 months 1

Moderate Deficiency (12.5-24 ng/mL)

• 50,000 IU weekly for 4-6 weeks (total 200,000-300,000 IU) 1, 4

Mild Deficiency (25-49 ng/mL)

• 800-1,000 IU daily or 50,000 IU monthly 1

Special Populations Requiring Dose Adjustments

• Malabsorption patients: 50,000 IU 1-3 times weekly 1
• Obese patients: 2-3 times higher doses (up to 7,000 IU daily) 1
• Liver disease patients: Higher doses due to impaired hepatic 25-hydroxylation 1

Weight-Based Dosing Formula

For precision dosing, the following formula can be used:

• Dose (IU) = 40 × (75 - current serum 25-OHD₃) × body weight (kg) 4

Administration Guidelines for IM Injection

When using ergocalciferol (vitamin D2) injection:

• Important safety note: The therapeutic to toxic dose range is narrow 5
• Administration technique: Deep intramuscular injection in gluteal muscle
• Frequency options:
  • Single annual dose of 600,000 IU (shown effective in maintaining levels >50 nmol/L for 12 months) 3
  • Multiple smaller doses as per patient needs and monitoring

Monitoring Protocol

• Check calcium and phosphorus at 1 month after initiation or dose change 1
• Check 25(OH)D levels at least 3 months after starting supplementation 1
• Monitor yearly once target level is achieved 1
• For patients receiving high doses, monitor urine calcium/creatinine ratio to detect hypercalciuria 3

Important Considerations and Cautions

• Target level: Aim for serum 25(OH)D >50 nmol/L (20 ng/mL), though some evidence suggests benefits for levels >75 nmol/L (30 ng/mL) 6
• Avoid single very large doses: Single doses of 300,000-500,000 IU should be avoided due to increased risk of falls and fractures 2
• Vitamin D form: Cholecalciferol (D3) is generally preferred over ergocalciferol (D2) due to higher bioefficacy 1, 7
• Calcium supplementation: Ensure adequate calcium intake (1000-1500 mg daily) alongside vitamin D for optimal bone health 1
• Potential complications: Monitor for hypercalcemia and hypercalciuria, especially with high-dose therapy 3

Special Situations

• Emergency correction: For rapid correction in critical situations (ICU patients, severe infections), calcifediol [25(OH)D] may be preferred as it raises serum levels more quickly 7
• Renal failure: Different dosing considerations apply; calcitriol may be necessary instead of cholecalciferol 7

By following these evidence-based guidelines and carefully monitoring patients, vitamin D deficiency can be effectively treated while minimizing risks of adverse effects.