Iron deficiency vs anaemia (anemia): what the terms mean

The words get used interchangeably, which makes reports and appointments harder to follow than they need to be. They describe three different things.

• Iron deficiency means the body’s supply or stores of iron are low.
• Anaemia (spelled anemia in the United States) means there are fewer red blood cells, or less haemoglobin in them, than expected. It has several possible causes.
• Iron deficiency anaemia is anaemia caused by a lack of iron. The body needs iron to make haemoglobin, the part of red blood cells that carries oxygen.

MedlinePlus notes that low iron often causes no symptoms until it is very low, which is one reason doctors sometimes order iron tests for people at higher risk even when they feel well.

What the NHS lists as causes

The NHS describes iron deficiency anaemia as most often caused by blood loss or by pregnancy, when the body needs more iron. Its list of causes includes:

• Heavy periods.
• Pregnancy, where it is most often due to low dietary iron.
• Bleeding in the stomach or bowel, which can come from medicines such as anti-inflammatory painkillers, ulcers, inflammation of the gut, piles and, less commonly, cancers of the stomach or bowel.
• Any other condition or event that causes blood loss.

How it is usually found

The NHS says a GP will ask about your history and arrange a full blood count, which checks the red blood cells and needs no preparation. Depending on the cause, further tests may follow, such as a test of a stool sample for hidden blood or a referral to a specialist. Other iron tests, including ferritin, are covered in the guide to iron blood tests.

Why the cause matters

The NHS says treatment starts with the underlying cause, such as heavy periods or an ulcer, alongside iron tablets and diet. That is why a result on its own is rarely the whole story, and why a record of dates, units and symptoms helps whoever is trying to work out the cause.