Iron deficiency anemia (IDA) is a common problem worldwide, whose cause is typically attributed to an improper diet and chronic blood loss. Lower iron absorption by the intestine, deficiency in dietary iron intake, increased iron requirements, and iron loss due to bleeding are the major causes of IDA. Iron loss during menstruation is the most common cause of IDA in women. Autoimmune atrophic gastritis and infection with Helicobacter pylori can also cause IDA by decreasing iron absorption in the intestines. In addition to these common causes, IRIDA may be caused by germline mutations of TMPRSS6. Homozygosity for the TMPRSS6 rs855791 C genotype has an active role in protecting women at reproductive age, against IDA, especially in those with menorrhagia. TF, TFR2, and TMPRSS6 polymorphisms are mainly associated with decreased iron levels, but only mutations in TMPRSS6 are genetic risk factors for iron deficiency and IDA.