I've tried taking vitamin D bc heard it was so great. After taking 1000 ui a day for a week or two, I will start to experience mood issues like increased anger and anxiety which will go away after a couple days of stopping. I have heard of others with this complaint as well, but I do not know why. ChatGPT suggests something about magnesium and calcium levels, but it's certainly not a commonly talked about side effect…
Maybe you have some sort of sensitivity to medium in which its dissolved?