I've been interested in large doses of vitamin d for obesity, I was obese as a kid and still carry more fat than I'd like, but what do you think about vitamin d being potentially toxic as it builds up? Do you take high doses for a few months and then take a few months off?
Jiggzz has the answer pretty much.
My girlfriend has a rare autoimmune disease that I found a study from 1930 showing 600,000 iu/day of vitamin D put into remission. That dose scared me without access to bloodwork (her pcp sucks big time). But I risked it for MONTHS at 200,000 iu. Not recommending this.
I have taken 20,000 iu for a year with no issues at all, but I think this could push the limits. I don't have bloods to test, again, so I dropped that to 10K after that.
My dad had a stroke in October 2018. I put him on 200,000/week for about 2 months, then dropped it back to 20,000 a day for about 6 months and his bloods came back at 80 ng/ml so I dropped it to 10K.
I am not recommending there are no toxicity concerns, but I have taken risks and you can learn a little from it.
I would recommend 10K/day if you are NOT in the sun a lot. If you are a landscaper or something, 5K would be better.
There is a case of a guy recently taking 10K per day for a while and sunbathing whike continuing to take this dose. He wound up in the ER from that. So if you do get sun, be more careful. I have an office job and get little sun.
I believe you can get something like 20,000-30,000 iu from the sun in about 30 minutes if you have your shirt off. Not sure of the exact numbers, but it is something like that.
All in all, don't be crazy like me and you will likely not have to worry too much.