I've never witnessed Hypervitaminosis D in real life, although it's theoretically possible. Vitamin D deficiency is much more common.

The plasma calcium level is very complicated, and it can't solely blamed on Vitamin D intake. The functioning of the parathyroids and kidneys have as much, if not more, to do with it, and it's a complicated feedback mechanism. Any endocrinologists here who can explain it better?

If you live near Seattle, or are not exposed to sunlight very often, then maybe some supplemental Vitamin D and calcium is in order.

Disclaimer: This is not medical advice. Always consult your physician before changing medications / supplements :)

Isn't the toxicity danger something like > 40K IU / day for some extended time period on the order of weeks? I'd guess most people are going to take 5-10K IU daily...5K is also the version most commonly presented in Amazon searches for D3.

I don't have the right experience to give you a definite answer on this. All I can say is that my doctor had me reduce my dosage, which was 5K IU daily, because my levels were starting to get too high. So it's easy for me to see how someone reading this article would decide to take 10-20K ICU a day and quickly get to levels a doctor would consider out of healthy range.

5K IU/day over the long term is the upper limit of safe D3 supplementation.

To avoid the vascular problems, many people recommend taking vitamin K2 at the same time.

Don't all the fat-soluble vitamins have this issue?

if you are pissing all the time / vomiting that seems like a good feedback that you are doing it wrong.