It is for some people. I currently need to take 100k iu/week in order to be on the low end of normal.
I was on 150k iu, but I had to switch doctors. The new idiot didn’t believe me and just told me take an OTC pill a day.
I left that guy. The next time I got checked, I was in the single digits. The new one didn’t really believe me either. Each winter visit I’ve been low and she just keeps adding another pill. I suspect I’ll be back up to 150k then.