RT Journal Article SR Electronic T1 Frequent blood donors risk iron deficiency JF Canadian Medical Association Journal JO CMAJ FD Canadian Medical Association SP 817 OP 817 DO 10.1503/cmaj.109-4807 VO 186 IS 11 A1 Miriam Shuchman YR 2014 UL http://www.cmaj.ca/content/186/11/817.abstract AB