An exception might be if blood levels are low, but you have to spring for a lab test to find that out.
My 97 YO mother just had her serum D tested -- was in normal range.
Although the researchers identified 137 different health outcomes associated with vitamin D levels, they found that only 10 of these outcomes had been comprehensively tested in trials, and only one outcome - that an infant's birth weight is linked to a mother's vitamin D levels in late pregnancy - had enough evidence to deem it a "benefit."
We live in Washington State. The sunshine here is rare during the rainy late fall, winter, and spring.
The last two days it has rained with temps in the mid-sixties to mid-seventies. This means staying inside the house for me. If it wasn’t for the oral dose of D3, I probably wouldn’t be receiving that vitamin.