Vitamin D3 Conversion: 46.4 nmol/L to ng/mL
46.4 nmol/L equals 18.6 ng/mL 1
Conversion Formula
- The standard conversion for 25-hydroxyvitamin D [25(OH)D] is: 1 nmol/L = 0.4 ng/mL 1
- Therefore: 46.4 nmol/L × 0.4 = 18.6 ng/mL
- The reverse conversion is: 1 ng/mL = 2.5 nmol/L 1
Clinical Interpretation of This Level
This level (18.6 ng/mL) represents vitamin D deficiency requiring treatment 2, 3
- Vitamin D deficiency is defined as serum 25(OH)D below 20 ng/mL 2
- Your level of 18.6 ng/mL falls just below this threshold and requires active supplementation 2, 3
- The target level for optimal health is at least 30 ng/mL for anti-fracture efficacy and musculoskeletal health 2, 3
- Severe deficiency (below 10-12 ng/mL) dramatically increases risk for osteomalacia and rickets, but your level does not meet this threshold 1
Recommended Treatment Protocol
The standard loading regimen is 50,000 IU of vitamin D3 (cholecalciferol) once weekly for 8-12 weeks 2, 3
- Cholecalciferol (D3) is strongly preferred over ergocalciferol (D2) because it maintains serum levels longer and has superior bioavailability 2, 4
- After the loading phase, transition to maintenance therapy with 800-2,000 IU daily 2, 3
- Ensure adequate calcium intake of 1,000-1,500 mg daily from diet plus supplements if needed 2, 3
- Recheck 25(OH)D levels 3 months after starting treatment to confirm adequate response 2, 3
Important Considerations
- Using the rule of thumb, an intake of 1,000 IU vitamin D daily increases serum 25(OH)D by approximately 10 ng/mL, though individual responses vary 2
- To raise your level from 18.6 ng/mL to the target of 30 ng/mL requires an increase of approximately 11.4 ng/mL (or 28.5 nmol/L) 1
- Daily doses up to 4,000 IU are generally safe for adults, with some evidence supporting up to 10,000 IU daily for several months without adverse effects 2, 5