Is vitamin D 1,25 the same as vitamin D, 25-OH?

No, vitamin D 1,25 is not the same as vitamin D, 25-OH. Vitamin D, 25-OH (calcidiol) the major circulating form of vitamin D. Vitamin D 1,25 (calcitriol) is the most potent form of vitamin D. Briefly, dietary vitamin D3 gets turned into vitamin D, 25-OH by the liver. Then, the kidneys turn vitamin D, 25-OH into vitamin D 1,25. For more information, visit https://lpi.oregonstate.edu/mic/health-disease/skin-health/vitamin-D