I get my vitamin D levels check every quarter because of my kidney failure. Based on my past experiments, I'd say if you are in the bay area, walking in the noo

I get my vitamin D levels check every quarter because of my kidney failure. Based on my past experiments, I'd say if you are in the bay area, walking in the noon sun for 15 minutes every workday would be enough to keep healthy vitamin D levels. In terms of supplements, about 1500 IU/day is enough during winter season.