When to Treat Vitamin D Deficiency
Treat vitamin D deficiency when serum 25-hydroxyvitamin D [25(OH)D] levels fall below 20 ng/mL (50 nmol/L), and strongly consider treatment for insufficiency (20-30 ng/mL) in patients with risk factors for bone disease, falls, or fractures. 1, 2, 3
Diagnostic Thresholds
- Deficiency: 25(OH)D < 20 ng/mL (50 nmol/L) - requires treatment 1, 3
- Severe deficiency: 25(OH)D < 10-12 ng/mL - significantly increases risk for osteomalacia and rickets, demands urgent treatment 1, 2
- Insufficiency: 25(OH)D 20-30 ng/mL - treat if patient has osteoporosis, fracture risk, falls, or is elderly 1
Important caveat: Inflammation (CRP > 40 mg/L) can artificially lower vitamin D levels, so interpret results cautiously in acutely ill patients 1
Treatment Protocols by Severity
For Deficiency (< 20 ng/mL)
Loading phase:
- Ergocalciferol (vitamin D2) or cholecalciferol (vitamin D3) 50,000 IU once weekly for 8-12 weeks 1, 2, 3
- Cholecalciferol is preferred as it maintains serum levels longer and has superior bioavailability 1, 4
Maintenance phase:
- Transition to 1,500-2,000 IU daily after completing loading dose 1, 2
- Alternative: 50,000 IU monthly (equivalent to approximately 1,600 IU daily) 5, 1
For Severe Deficiency (< 10 ng/mL)
- 50,000 IU weekly for 12 weeks, then monthly maintenance 1
- Consider higher maintenance doses (2,000 IU daily minimum) 1
For Insufficiency (20-30 ng/mL)
- Add 1,000 IU daily to current intake and recheck in 3 months 1
- Target goal: achieve 25(OH)D ≥ 30 ng/mL 1, 2
Special Populations Requiring Treatment
Elderly Patients (≥ 65 years)
- Treat with minimum 800 IU daily even without baseline measurement 1
- Higher doses (700-1,000 IU daily) reduce fall and fracture risk 1
High-Risk Groups Requiring Empiric Treatment
- Dark-skinned or veiled individuals with limited sun exposure: 800 IU daily without baseline testing 1
- Institutionalized individuals: 800 IU daily 1
- Pregnant and breastfeeding women: routine supplementation recommended 6
Chronic Kidney Disease (CKD)
- Treat deficiency in CKD stages 3-5 with ergocalciferol or cholecalciferol (not active vitamin D analogs like calcitriol) 5
- For GFR 20-60 mL/min/1.73m², use standard nutritional vitamin D replacement 5, 1
Malabsorption Syndromes
- Post-bariatric surgery, inflammatory bowel disease, pancreatic insufficiency: consider intramuscular (IM) vitamin D 50,000 IU as it achieves higher levels than oral supplementation 1
- IM route is more effective than oral in these patients 1
Target Levels and Monitoring
Treatment goals:
- Minimum target: 25(OH)D ≥ 30 ng/mL for optimal bone health and anti-fracture efficacy 1, 2
- Anti-fall efficacy begins at ≥ 24 ng/mL 1
- Upper safety limit: 100 ng/mL 1
Monitoring schedule:
- Recheck 25(OH)D after 3-6 months of treatment 1, 2
- If using intermittent dosing (weekly/monthly), measure just before next scheduled dose 1
- Individual response varies due to genetic factors in vitamin D metabolism 1
Essential Co-Interventions
- Ensure adequate calcium intake: 1,000-1,500 mg daily from diet plus supplements if needed 5, 1
- Calcium supplements should be taken in divided doses (no more than 600 mg at once) 1
- Weight-bearing exercise 30 minutes, 3 days per week 5
Critical Pitfalls to Avoid
- Do NOT use active vitamin D analogs (calcitriol, alfacalcidol, doxercalciferol, paricalcitol) to treat nutritional vitamin D deficiency - these do not correct 25(OH)D levels 5
- Avoid single very large doses (> 300,000 IU) as they may be inefficient or harmful 1
- Do not supplement patients with normal vitamin D levels - benefits are only seen in those with documented deficiency 1
- Vitamin D deficiency should be corrected before initiating bisphosphonates to prevent hypocalcemia 5