It is my understanding that you are supposed to take b2 to "encourage" your liver to release iron. I can't see any reason why a person who eats meat and/or lives in a country where food is plentiful would need to supplement with iron. It seems to me to be more a matter of getting your liver to release it into your blood and/or storing it in your tissues rather than absorbing it from food or supplements. I took manganese by itself for almost 2 weeks and had cold extremities and chills; they stopped when I added in small amounts of b2 as well as small amounts of b12 (blood building vitamins). This also increased my serum iron levels by a small amount (67 to 77) and caused my ferritin levels to increase from 3 to 14 in less than 2 months.