There are three main causes of iron deficiency.

• not eating enough iron-rich foods
• trouble absorbing iron
• blood loss

If you have iron deficiency, it’s important to know the cause so you can get the right treatment. Also investigating why you may have iron deficiency may mean a serious disease won’t be overlooked, plus it will help prevent the deficiency coming back.

Not eating enough iron-rich foods

While your body can store iron, it can’t make it. You need to get iron from food. Red meat is the best source of iron, although you can also get some iron from other meats. Some plant foods also contain iron; some vegetables and pulses have more iron than others.

Some people need more iron than others. The people who need most iron are children, teenagers (especially girls), females who have periods, pregnant women and breastfeeding women.

Babies need breast milk or iron-fortified formula for the first year. Babies who have cow's milk instead are more likely to get iron deficiency.

Trouble absorbing iron

Iron in food is absorbed through your stomach and bowel. Some health conditions affect how much iron you absorb, such as coeliac disease. If you’ve had stomach surgery, that can also affect how much iron you can absorb.

The iron in plant-based foods is much harder to absorb than the iron in animal foods. So if you’re a vegetarian or vegan, it’s important to understand how to prepare iron-rich foods to make sure you absorb as much iron as possible.

Blood loss

If you lose blood through any sort of bleeding, this means you lose iron too.

The main causes of excess blood loss are:

• having heavy menstrual periods
• bleeding in the stomach or bowel — this may be from medicines such as aspirin or other anti-inflammatory medicines, ulcers, bowel polyps or cancer

Other causes can include giving blood too regularly, losing blood due to surgery, some gut conditions such as inflammatory bowel disease, and infection with parasites such as hookworms.