Consultant Physician, medical researcher and author, Dr David Grimes conducted much original research on the essential to life Vitamin D. Buy his inexpensive latest book here. https://yorkbookshop.com/health-and-p... 2 minor corrections - 150nmol/L = 60ng/mL (not 80ng/mL as stated and at 2min 27secs) 57min 11 secs Calcifidiol appears in the BNF here: https://bnf.nice.org.uk/drugs/calcife... and medicinal form here https://bnf.nice.org.uk/drugs/calcife...