A daily dose of 2000-4000 is enough and is very safe.

42% of Americans are deficient, much more the darker your skin is.

https://www.healthline.com/nutrition/vitamin-d-deficiency-sy...

Could help explain why COVID-19 is much more severe (on average) if you’re black...

It's definitely a factor!

The literature states 1000-2000 is safe for basically anyone, but you really shouldn't be taking more than that without actually going to a doctor and getting your deficiency confirmed. Just because you have darker skin, it doesn't mean taking a higher oral dose won't cause other issues.

IIRC daily doses above 2000 over a longer timespan can (infrequently) cause your vitamin B12 levels to fall off, and/or the amount of calcium in your blood to build up, so your doctor might want to schedule a follow-up appointment after some time has passed to make sure those levels still look okay, and adjust supplements for those variables accordingly.

If you have an easy access doctor around to ask, I completely agree with that!

If you're not going to see a doctor about this, for laziness/poverty/whatever reasons, I think the average risk from not taking Vitamin D is vastly bigger than the risk from taking it.

You would have to take crazy amounts of vitamin D - more than 250 mcg (10000 IU) - for it to be toxic [0][1].

[0] https://academic.oup.com/ajcn/article/85/1/6/4649294

[1] https://asbmr.onlinelibrary.wiley.com/doi/full/10.1359/jbmr....

Over a prolonged period of time...

I got my D3 levels up to 478nmol/L according to the UK NHS Vit D blood spot service. Supplemented up to starting point of around 200-240nmol/L and then spent the summer outside with top off working on laptop. Never felt so good. Bought some Lizard flo tubes after that to bask under after I was craving a suntan one winter. Odd feeling, but I was also doing alot of magnesium sulphate (Mag oil) topically which helps and some zinc orally. The Mag oil stings the skin much like Deep Heat, so be warned and thinner skinned individuals will experience more pain.

400mg = 400000mcg = 16000000ui https://www.azcalculator.com/calc/vitamin-d-mcg-iu-converter...

This is kind of a silly thing to be worried about with Vitamin D.

Yes it's fat soluble. But the amount you would need to take in supplements to cause a problem is enormous. (Every vitamin is different)

You could probably take an entire bottle and you'd be fine.

The patients in this study were being given 10x the RDA, about 20k IU/day.

You can very very easily get 25k IU out in the sun and your body has no issues.

It's safe to take 2000IU/day and make sure to get sun if possible.

A few days ago, a blog post by a physician was stressing this same point. She was suggesting to be especially cautious with high doses.

High doses don't have much of a health benefit either. It's low doses on a daily basis.

Through in the UK the NHS were handing out high doses of Vitamin D like cotton candy last winter.