I’m the author. In reading the comments here, there are some common questions and misunderstandings that I would like to address.

First, about the patient being an outlier:

I wrote the article because I see cases like hers pretty frequently, and it’s frustrating. She is an outlier in the severity of her symptoms, but not an outlier in getting Vitamin D toxicity from 5,000 units daily. I get at least one patient a week contacting me about their high calcium levels - and when I get into their medical history it is clear that Vitamin D is the cause of the high calcium. In most cases, they are on 5,000 units daily. Stopping the Vitamin D allows the calcium to drop back to normal, though it usually takes a few months.

Regarding those of you on high doses who are doing just fine:

I believe you. This actually doesn’t change the point of my article. I even state in there that some people can take high doses and not develop any problems. And some people need higher doses of Vitamin D because they have problems with Vitamin D metabolism. In addition, there are people on higher doses because they are treating other medical conditions like psoriasis. The point of my article is that you need to monitor your calcium and Vitamin D levels if you are going to take these higher doses. And you need to know the risks of taking high-dose Vitamin D over a long period of time. There are risks to any medication; treat Vitamin D like the medication that it is.

About the multiple studies posted here with statements that high-dose Vitamin D is safe and toxicity is rare:

It's really important to follow the sources. I cannot say this enough. Most of the articles cited are review articles that are simply repeating things from other review articles. You have to keep following the citations back to find the actual studies in which humans consumed Vitamin D.

When you do that, you find very few human studies on high doses. The larger studies on Vitamin D will typically use more moderate doses, such as 2,000 units daily. Most of the articles on high doses are case reports in which someone took outrageous amounts of Vitamin D and eventually got really sick from it. These case reports don’t tell us where the safe level is, only that some people can tolerate outrageous doses for a short period of time.

But isn’t there an actual study showing that high doses are safe? One controlled study that many of the review articles refer back to is a small study done in men in high latitudes in winter, when skin production of Vitamin D is decreased. It consisted of a small number of patients who were randomized to receive different amounts of Vitamin D, from none to 10,000 units daily. Only a small number actually got 10,000 units a day, the highest dose. And this was over a period of just 5 months, in the winter, in high latitude, when it is difficult to get skin production of Vitamin D. You can read the article here: https://pubmed.ncbi.nlm.nih.gov/12499343/ Also note that in this study, they found that adequate Vitamin D levels were maintained with doses well under 10,000 units daily.

A few of the review articles lead back to Michael Holick, controversial figure. He is well-known for pushing high doses of Vitamin D. Please read this NY Times article for a great summary of the issues here: https://www.nytimes.com/2018/08/18/business/vitamin-d-michae...

Regarding skin production of Vitamin D and why you don’t overdose on the sun:

Others mentioned this in their responses, but just to reiterate: you can’t get toxic levels of Vitamin D from being in the sun, because of the complex interactions that occur with UVB exposure. For those who want a very detailed explanation, read this article: https://www.tandfonline.com/doi/full/10.4161/derm.24494. TL;DR version: after a certain amount of previtamin D and Vitamin D3 is made as a result of UVB radiation, excess exposure then causes breakdown of these into products that are inactive, so you get to an equilibrium where you can’t make more Vitamin D even with more sun exposure.

And for those who think I am somehow anti-Vitamin D:

I take Vitamin D, and recommend it to patients all the time (unless they have high calcium). I recommend moderate amounts, since for most people a dose of 1,000 to 2,000 units daily is more than enough. I do have patients who need to take much higher doses, and I have some patients on 5,000 units daily who are doing just fine. There are even rare patients who need more than that. The key here is that I’m monitoring their calcium and Vitamin D levels, and I only recommend 5,000 units daily if there is some evidence that they require it.

About selling high doses in pharmacies:

I really don’t like that in the US you can pretty easily buy 10,000 unit Vitamin D pills over the counter at common pharmacies (example: https://www.walgreens.com/store/c/nature's-bounty-d3-10,000-.... I would prefer that pharmacies sold Vitamin D in doses of 1,000 or 2,000 units, rather than 5,000 units, since the lower doses are almost always safe, but the higher doses may not be. Someone mentioned that Tylenol and ibuprofen are also dangerous, but available over the counter. This is not exactly the same thing, since those bottles are generally very conservative in how much they recommend taking, with strict warnings about not taking too much. This is not the case with most Vitamin D bottles.

If you want more info on Vitamin D, I wrote a couple other posts that cover some important background information and then the evidence for Vitamin D:
Part 1, Basics of Vitamin D: https://www.devaboone.com/post/vitamin-d-part-1-back-to-basi...
Part 3, Evidence for supplementation: https://www.devaboone.com/post/vitamin-d-part-3-the-evidence

Note that I wrote these several years ago in 2020. There have been more trials published since then, but the results are similar.