I was taking 10,000 IU/day and had a blood test done. My PCP advised me to throttle back on it.
I am on medicare and have to go twice a year to the doc and get bloodwork each time. I had been taking 10k d3 and he told me the proper level number and 5k keeps it there. I do bump it up when some bug is going around town. It is like getting sunshine. You get too much daily you see some changes like loss of appetite.