Women tend to have higher iron requirements than men, and iron deficiency is most prevalent among women due to loss of blood during menstruation and pregnancy. Iron is an important nutrient because your body needs it to make the protein called haemoglobin. Without haemoglobin your red blood cells can't carry oxygen from your lungs to the rest of your body. A lack of iron can lead to feeling tired or having no energy. The amount of iron suggested by the NHS is around 8.7 mg a day for men over 18 and 14.8 mg a day for women aged 18-50 years.