I take 10,000 i.u. per day.
No flu shots, no shingles shots, no irradiation.
Healthy as a horse and my early breast cancer has mis appeared also.
Bingo on the K2..critical for D3 uptake.
I haven’t been sick since I began taking Vit D religiously in 2007. I just never did know how much to take - I consume 2000iu right now but don’t know if it is enough. I’m glad you are doing well!