Vitamin D₃ 333 mg Conversion to International Units
333 mg of vitamin D₃ (cholecalciferol) equals 13,320,000 IU (international units).
Conversion Formula and Context
- The standard conversion for vitamin D₃ is: 1 mg = 40,000 IU 1, 2
- Therefore: 333 mg × 40,000 IU/mg = 13,320,000 IU 1
Critical Safety Warning
This dose is extraordinarily dangerous and represents a potentially fatal overdose. 1, 3
- The upper safety limit for serum 25-hydroxyvitamin D is 100 ng/mL; toxicity typically occurs with prolonged daily doses exceeding 10,000 IU or serum levels above 100 ng/mL 3, 4
- A single dose of 13.3 million IU is more than 1,300 times the safe daily upper limit of 4,000–10,000 IU 3, 4
- Vitamin D toxicity manifests as hypercalcemia, hyperphosphatemia, suppressed parathyroid hormone, and hypercalciuria, which can cause nausea, vomiting, weakness, confusion, and severe renal impairment 1, 3
- Single mega-doses exceeding 300,000 IU should be avoided as they are inefficient and potentially harmful 3
Likely Explanation
- This appears to be a labeling or transcription error—vitamin D₃ supplements are typically dosed in micrograms (μg) or IU, not milligrams 1, 2
- Common therapeutic doses range from 600–50,000 IU (0.015–1.25 mg), not 333 mg 1, 3, 2
- The FDA-approved high-potency formulation is 1.25 mg (50,000 IU) per capsule, taken weekly 2
Immediate Action Required
If this dose has been ingested:
- Discontinue all vitamin D supplementation immediately 3
- Measure serum calcium, phosphorus, and 25-hydroxyvitamin D urgently to assess for toxicity 3
- Seek emergency medical evaluation if any symptoms of hypercalcemia are present (nausea, vomiting, confusion, weakness) 3
- Increase oral hydration to promote calciuresis if calcium is elevated 3
If this is a labeling question before administration: