I took 10,000 ui a day for over a year to build my vit d level up to 176. I have multiple sclerosis. My goal is 200, have done a tone of research on the topic, toxicity levels, etc... For 12 years in a row, have had a relapse every winter, past winter didn't have one. One could say this is a coincedence, I say no.
In the summer I am always out in the sun alday, mostly every day, shorts, t-shirt, etc... For some reason, my body doesn't absorb the vit d good. I have fair skin, that tans very well. Anyways, I just wanted to share my knowledge to help others.