Reference ranges for haemoglobin and ferritin in women of reproductive age are widely reported showing values that are lower than equivalent aged males. Similar values would be expected in the absence of different biological requirements. While reference ranges have been derived from data on large populations, it is likely that these populations have included significant numbers of women who are iron deficient in view of menstrual blood loss and poor dietary intake. Populations with a daily iron intake in excess of 100mg have shown that iron deficiency in females is rare. Studies reporting bone marrow with iron stains from 50 years ago pointed out that significant numbers of women were iron deficient and more recently serum ferritin studies have confirmed this. However, a large number of women in the Western world spend a significant part of their lives in a negative iron balance due to a combination of poor diet and menstrual blood loss. The presence of haem iron in the diet of humans enhances non-haem iron absorption but dietary surveys consistently report that women's diet is deficient in iron. Furthermore, the typical Western diet contains many common foods that limit iron absorption. It appears that lower haemoglobin and ferritin values in menstruating women have been accepted as normal rather than possibly representing widespread iron deficiency. Reference ranges should be re-evaluated in populations proven to be iron replete.