What causes low iron?

This answer shows a full list of all the diseases and conditions listed as a possible cause of Low blood iron by various sources. Acute Blood loss Blood test shows falsely decreased iron levels - e.g. error in collection or storage Breastfeeding Chronic Blood loss Chronic haematuria Chronic haemoptysis Colorectal malignancy Decreased acidity in stomach (hypochlorhydria) Decreased dietary intake Gastric malignancy Gastritis Gastrointestinal bleeding Hookworm Infancy Inflammatory bowel diseases Medications causing decreased stomach acidity Menstruation NSAID/aspirin use Parasites Peptic ulcer Pregnancy Puberty