From the Guidelines
To convert 10,000 IU of vitamin D3 to vitamin D2, you would need approximately 12,500 IU of vitamin D2, considering vitamin D3 is more effective in raising 25(OH)D concentrations and maintaining those levels for a longer time 1. When considering this conversion, it's essential to note that vitamin D3 and D2 are metabolized differently, with vitamin D3 being more potent in raising and maintaining 25(OH)D levels 1.
- The NCCN task force report suggests that vitamin D should ideally be supplemented in amounts sufficient to bring serum 25(OH)D levels to 30 ng/ml (75 nmol/L) or higher 1.
- However, it's crucial to be aware that 10,000 IU daily is a very high dose of vitamin D that exceeds typical recommended daily allowances and should only be taken under medical supervision 1.
- High doses like this are typically used for short-term correction of significant deficiency rather than long-term maintenance, and regular monitoring of vitamin D levels through blood tests is necessary to avoid reaching toxic levels 1.
- The potential side effects of excessive vitamin D, such as hypercalcemia, hyperphosphatemia, and activation of bone resorption, should also be considered 1.
- Current expert opinion recommends 800 to 1000 IU of vitamin D daily for adults older than age 50, and the NCCN Bone Health in Cancer Care Task Force suggests these ranges for younger patients at risk for cancer treatment–associated bone loss 1.
From the Research
Vitamin D3 to D2 Dose Conversion
- The provided studies do not directly address the conversion of vitamin D3 10,000 IU per day to a vitamin D2 dose.
- However, the studies provide information on the safety and efficacy of high-dose vitamin D3 supplementation, which may be useful in understanding the potential effects of converting to a vitamin D2 dose.
- A study published in 2020 2 found that vitamin D3 doses up to 10,000 IU/day were safe and well-tolerated in healthy adults.
- Another study published in 2014 3 developed a predictive equation to guide vitamin D replacement dose in patients, but it does not provide a direct conversion from vitamin D3 to D2.
- A 2025 study 4 compared the effectiveness of different vitamin D3 supplementation doses in young healthy individuals, but it does not address vitamin D2.
- A 2017 study 5 reported on the safety of daily oral dosing with up to 60,000 IU of vitamin D3 for 2 to 6 years in adult males, but it does not provide information on vitamin D2.
- A 2004 study 6 compared the effects of vitamin D3 adequate intake versus 100 mcg (4000 IU) per day on biochemical responses and wellbeing, but it does not address vitamin D2 or provide a direct conversion from vitamin D3 to D2.
Key Findings
- The safety and efficacy of high-dose vitamin D3 supplementation have been established in several studies 2, 3, 4, 5, 6.
- However, there is no direct evidence to support a specific conversion of vitamin D3 10,000 IU per day to a vitamin D2 dose.
- Further research is needed to determine the equivalent dose of vitamin D2 for a given dose of vitamin D3.