The prescription Vit. D is usually the D2 form and it did nothing for me. Tried for years! There is a lot of info on Vit D 3 here in both the Supplement forum https://forum.lowcarber.org/showthread.php?t=452398 and a buddy group linked within this thread.

I try to get mine first from sun and then from food. Food sources listed here: https://optimisingnutrition.com/vit...ods/#more-18550 I still take an OTC D3 supplement in the winter because as a cancer survivor Want to keep level high, around 80, and measure it with a blood test 1-2 times a year.