I am not aware of any documented toxicity resulting from oral D3 @ 5,000 IU/day, but it is certainly possible.
Without question, Vitamin D3 from Sun is the best form and self-limiting b/c its sulfated, whereas no known enzyme exists to sulfate orally administered D3, leaving it potentially much more active. This is an area of much needed research in the vitamin D3 field, which could minimize much confusion in research findings.
However, it is established that "10–15 min whole-body exposure to peak summer sun will generate and release up to 20,000 IU vitamin D-3 into the circulation."
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