If your iron is low, your body doesn't get the oxygen it needs to function as it should. This is why you can feel exhausted, breathless, and dizzy when your iron is low. Low iron can be due to dietary factors; you don't eat enough iron for your body's needs, or your body can't absorb iron properly because you have a gut or bowel condition like coeliac disease or Crohn's. Low iron is commonly caused by blood loss from menstruation or internal bleeding, often in the digestive tract. Iron deficiency anaemia can also develop in pregnancy.
Iron deficiency is the most prevalent nutritional problem in the UK and worldwide. In developed countries, around 10-20% of women of childbearing age are anaemic.