What is the treatment for a 37-year-old patient with Vitamin D deficiency (hypovitaminosis D), with a level of 18 nmol/L?

Treatment for Vitamin D Deficiency (18 nmol/L)

For a 37-year-old patient with severe vitamin D deficiency (18 nmol/L), treatment should begin with a loading dose of 50,000 IU of vitamin D weekly for 8 weeks, followed by maintenance therapy of 1,000-2,000 IU daily. 1

Assessment of Deficiency Severity

The patient's vitamin D level of 18 nmol/L (7.2 ng/mL) indicates severe vitamin D deficiency:

• Severe deficiency: <25-30 nmol/L (<10-12 ng/mL) 2
• Normal range: 50-150 nmol/L (20-60 ng/mL)
• Optimal target: 75-100 nmol/L (30-40 ng/mL) 1

Treatment Protocol

Initial Loading Phase

• Loading dose regimen: 50,000 IU vitamin D weekly for 8 weeks 1, 3
• This rapid repletion approach is necessary because standard daily doses would take many weeks to normalize severely low vitamin D levels 2

Maintenance Phase

• After completion of loading phase: 1,000-2,000 IU daily 1, 4
• Higher maintenance doses (2,000 IU/day) may be needed if risk factors for deficiency persist 4

Monitoring

• Check follow-up vitamin D level after 3 months of therapy 1
• Target level: 75-100 nmol/L (30-40 ng/mL) 1
• Adjust dose based on follow-up levels:
  • If level remains <50 nmol/L: increase maintenance dose
  • If level reaches target: continue maintenance dose

Considerations for Dosing

Several factors affect vitamin D dosing requirements:

• Starting serum concentration (lower levels require higher doses)
• Body mass index (higher BMI requires higher doses)
• Age (older age may require higher doses)
• Serum albumin concentration 5

On average, each 1,000 IU of vitamin D supplementation increases serum levels by approximately 10 ng/mL (25 nmol/L) 4, though individual responses vary.

Safety Considerations

• Vitamin D supplementation in doses up to 10,000 IU/day appears safe for most adults 6
• Monitor for hypercalcemia if using high doses, though this is rare at recommended therapeutic doses 7
• Ensure adequate calcium intake (800-1,200 mg/day), preferably from dietary sources rather than supplements 1
• Vitamin D toxicity typically occurs only at levels above 150 ng/mL (375 nmol/L) 1

Practical Implementation

1. Prescribe vitamin D3 (cholecalciferol) 50,000 IU once weekly for 8 weeks
2. After 8 weeks, transition to daily maintenance dose of 1,000-2,000 IU
3. Check vitamin D level after 3 months of therapy
4. Adjust maintenance dose based on follow-up level
5. Consider annual vitamin D testing once levels normalize 1

This approach balances the need for rapid correction of severe deficiency with long-term maintenance of adequate vitamin D status to improve bone health and reduce risk of falls and fractures.