It's not though. That is to say... people really ought to check their blood results and act appropriately.

The truth is that in northern latitudes, anyone with dark skin is simply unable to meet their vitamin D intake from sun exposure alone. In certain parts of America, and a lot of Europe, a dark skinned person spending the entire lit part of the day outside buck naked is still not enough to synthesize enough vitamin D to be sufficient. Supplementation or dietary ingestion is necessary.

For me, as a dark skinned person in a northern latitude, my levels were very low. Taking 2000 IU a day did nothing. I had to take 10000 IU a day in order to appreciably raise my Vit D levels. That is what we found after checking with a doctor. I would recommend anyone else do the same. 5000 IU + is typical for people with vitamin D deficiencies. Some doctors even recommend extremely high megadoses to reset your vitamin D intake.

Because it's really hard for your body to absorb, unless taken sublingually (or maybe with a fatty meal, given it's fat soluble).

All that matters is your serum level. 800IU may work for you, but you may need several times that. Best to just get it checked. People feel better at different levels, e.g., I seem to feel best around 35-40 ng/mL.

Check out Dr. Rhonda Patrick (@foundmyfitness) on the topic: https://www.youtube.com/watch?v=uc815fQn8iY.

Vitamin D is fat-soluble, so dosing daily isn't required (the excess is stored and not excreted in urine). The 5k and 10k IU pills are useful because you can pop a few on weekends (or whenever you remember) and don't need to build a daily habit.

There is evidence to say that the recommended dose is much much lower than what is beneficial.

Plus if you actually do OD, the symptoms are very apparent and treatment readily available.

Also to OD I think you need a LOT more than 5000 IU a day.

It would probably be wise to not post your opinion on things like vitamin dosages unless you're a medical doctor.

My doctor prescribed 1 week of 15000 IU a day, then a week of 10000 IU, then a running dose of 5000 IU a day. I've seen measurements of 50k IU from a day in the sun. 3000-5000 is not too much or "obscenely high" for many people, but as with literally everything like this, its best to consult a doctor about an individual's needs.

Yeah you can overdose [1]. It's not just what these people are getting in supplements, but also about what they are getting naturally.

[1] https://en.wikipedia.org/wiki/Hypervitaminosis_D

Do they actually make 5000IU pills?

I've been taking 1 pill of 1000IU whenever I stay inside an entire day without even 5 minutes outdoors, but I really don't know for sure what the recommended doses are.