It appears that a majority of people my be deficient. The blood serum measure of 25(OH)2D3 that are considered in the 'normal' range is based on how much D you need in order to not have D-deficiency diseases (e.g. rickets), and not based on an amount that may be optimal (and I think those 'normal' ranges are based on epidemiological, not randomized controlled trials). Those values also do not reflect activated D3 -- 25(OH)2D3 is not usable by the body in that form, and much of it goes through the liver, and then the kidneys, to get activated into 1,25(OH)2D3, which is the form that is actually used by the body. Studying tribes in natural settings (Masai warriors, for example), they have 2-4x (maybe more) the amount of D in their blood (25(OH)2D3). Also, it seems it's really difficult to take enough D to induce a toxic response. Yes, it's fat soluble, but that doesn't mean it's being stored in your body fat. You have to reach a level significantly higher than the normal range before any D is available for storage in body fat -- there is a graph in one of the talks, I think the first one, that shows that. Cases of toxicity so far have been of people taking millions of IUs of D3 per day over an extended time period, inadvertently. D has been reduced or eliminated from foods precisely because of the few cases where millions of IUs were being put into bottles of milk which wasn't supposed to happen. Europe banned D in foods IIRC. This was decades ago. Many are now deficient because they stay out of the sun or wear sunscreen. Surprisingly, taking much higher doses of D battles TB -- they now think that sending TB patients to solariums and warmer climates worked because they were getting more sun, and thus making more D. I've been taking 30,000-50,000 IUs a day for about two months now, not because of coronavirus, but because of these three talks by doctors and other evidence I've looked at. I do think, based on these talks, that the majority of individuals in this country and others have suboptimal D levels and D availability:
https://www.youtube.com/watch?v=B9SNfrE7P1s
https://www.youtube.com/watch?v=EP81YMvs4yI&feature=youtu.be...
https://www.youtube.com/watch?v=N20nyUTqiyY
/s.
