A 2004 study of 75 vegan women in Germany showed that iron deficiency was substantially more common among vegan young women (40%) than the baseline for adolescent girls and women (11%) in the United States. However, only 4% (n=3) had iron deficiency anemia which is about the same as baseline.
A 2015 study of 60 young women in India (30 vegetarians) showed that iron deficiency (low blood haemoglobin level) was substantially more common (100%) than the non-vegetarian group (54%) but severe iron deficiency anemia was not observed in either group.
A 2012 publication in MJA about Iron and vegetarian diets thoroughly summarized the existing literature.
Compared with meat-eaters, vegetarians may often have lower serum ferritin levels (although still within the normal range), even when their iron intakes are adequate, but the physiological impact of reduced ferritin levels in vegetarians is unknown at this time. Vegetarians may reduce their risk of low iron levels by eating foods rich in enhancers, such as vitamin C and organic acids.
In Western countries like Australia, where we enjoy a varied food supply, vegetarians are no more likely to suffer from iron deficiency anaemia than non-vegetarians. Low iron stores, without iron deficiency anaemia, have not been shown to adversely affect function. Iron deficiency clearly impairs function only when haemoglobin concentrations are measurably decreased, but this has not been shown across all studies. In the large European Prospective Investigation into Cancer and Nutrition (EPIC)-Oxford study of 43000 women, vegetarians and non-vegetarians had similar iron intakes and haemoglobin concentrations. Many studies in Western societies suggest there is little difference, if any, in iron status (measured by haemoglobin levels, haematocrit, total iron-binding capacity, transferrin saturation and serum iron levels) between vegetarians and non-vegetarians, but a number of studies suggest that vegetarians are at greater risk of having low iron stores (as reflected by serum ferritin).
Vegetarians and vegans are not at increased risk of iron deficiency anemia, despite usually having lower iron stores in the blood.