I have had my vitamin d level tested several times simply because I have lived in northern climes where you gotta wonder where you are at in the middle of the winter in regard to d-levels.
To be expected it was very low, can't remember the first test but low- 21 ng's I think, and consistent with your experience I had to work my arse off to get it up to 45-50 which is the top part of the 25 hydroxy test range. I was taking 15,000 units a day. Took me about three months. I didnt worry much about the high level because I was getting tests to monitor. The usual scare literature will say that if you are taking more than 700 units or so a day you are going to die. Don't count on it. It's bitch to build up in your blood and anything less than 150ng is not considered toxic and maybe some people could get up there but it would not be me. People get confused about vitamin d toxicity. Yes, it is highly toxic if you are a kid and think it is candy and a whole bottle of 5000 unit tablets at once because it overwhelms your liver but that is a different scenario.
As far as monitoring calcium, lots of people think that taking lots of vitamin d automatically leads to critically high levels of calcium. No it doesn't. It could but it is not the intake of vitamin d that increases the calcium, it is the increase in the blood serum level of vitamin d that does or could increase calcium. If you are taking lots of d but it is only causing your serum levels to come into a normal range then you are in a normal range of vitamin d. Vitamin D is actually not a vitamin - it is a hormone. One of its major jobs it to help absorb and move calcium around as needed. For most people having vitamin d raise their calcium level is a good thing. But,yeh why not measure along with everything else. Not to get to far into the weeds but Vitamin K is vitamin that calcium going where it should go rather than calcifying your arteries. Google more if needed.
Also, and I am sure you know this but just while we are here, I will add in that I hope you or anyone is taking Vitamin D3 rather than DL. a/k/a D2 but it will usually say DL on labels. They are both widely available and cheaper form is DL/D2. Don't do that. The absorption rate is much less than D3.
