Understanding iron deficiency anaemia: causes and treatments

Anaemia is a condition where you haven’t got enough healthy blood cells to carry oxygen around your body. There are several different types of anaemia, however, iron deficiency anaemia is the most common. Before we look at causes, risk factors and treatments for this condition, it’s helpful to understand how your blood cells are made.

Making blood cells

Your bone marrow is a sponge-like substance that sits in the centre of your bones. It’s responsible for making your blood cells. To do this, it needs some essential building blocks, including folate and vitamin B12. When making red blood cells, specifically, it also needs iron. This is because iron is used to make haemoglobin, a substance that allows your red blood cells to carry oxygen.

If your body lacks enough iron, your bone marrow can’t make enough healthy red blood cells.

Causes of iron deficiency anaemia

Iron deficiency anaemia can develop if there is not enough iron in your diet, your body can’t absorb the iron from your diet or due to blood loss.

Low iron levels

Low-iron diets are more common in vegans and vegetarians, which puts them at greater risk of developing iron deficiency anaemia. If you are a vegan or vegetarian, it is therefore important to include enough non-meat, iron-rich foods in your diet, such as tofu, soy beans, lentils and dark, leafy greens. If you’re concerned that you still may not be getting enough iron in your diet, speak to your GP about whether you should take supplements.

You are also at greater risk of developing iron deficiency anaemia if you have severe Crohn’s disease or coeliac disease. These autoimmune conditions can prevent your gut from properly absorbing iron from your food. 

Blood loss

Iron deficiency anaemia caused by blood loss is more common in women of reproductive age. This is because heavy periods can lead to significant blood loss. Women can also develop iron deficiency anaemia during pregnancy because your blood volume increases to support your growing baby. As your body produces more blood, you therefore need to consume more iron to meet the demands of producing more red blood cells.  

Iron deficiency anaemia due to blood loss in men is less common. However, it can occur due to unnoticed blood loss, which usually occurs in the gut. This should be investigated urgently to rule out bowel cancer. Blood loss in the gut can also be caused by other conditions that need treatment, such as ulcers and polyps.  

A less common cause of iron deficiency anaemia is regularly donating blood. This is usually picked up by the National Blood Transfusion Service, who will screen your blood before you donate to check your iron levels. If your iron levels are too low, you will not be able to donate blood and should see your GP in case there is an underlying cause preventing your body from effectively replenishing your iron stores in between blood donations. 

Symptoms of iron deficiency anaemia

The main symptoms of iron deficiency anaemia include tiredness and an inability to complete your usual physical activities, such as walking up the stairs or uphill, or running to catch a bus, without becoming breathless and extremely tired. You may also develop pale, cold extremities (eg your fingers and toes). 

It is important to note that the symptoms of tiredness and reduced tolerance to exercise are different from generally being unfit. Iron deficiency anaemia develops gradually and these symptoms steadily get worse, resulting in a gradual decline in your ability to perform everyday physical activities. 

Treating iron deficiency anaemia

Iron deficiency anaemia can be resolved by taking prescribed iron tablets or liquid iron medication for a defined period. Both cause your stools to become black, as excess iron that isn’t absorbed by your body is passed out. You may also develop stomach cramps and constipation.

If you can’t tolerate the side effects of iron tablets or liquid iron, or you have inflammatory bowel disease, your doctor may prescribe intravenous iron infusions where iron is directly administered into your bloodstream.

By taking additional iron, orally or intravenously, your body will be able to replenish its iron stores. This will allow your bone marrow to produce healthy red blood cells, resolving your iron deficiency anaemia. In cases of severe anaemia, you may need a blood transfusion.

It is also important to address the underlying cause of your iron deficiency anaemia — treatment varies depending on the specific cause. Once this has been resolved, your anaemia will improve and you can continue to follow your usual diet.

Author biography

Dr Gary Mackenzie is a Consultant Gastroenterologist at Spire Gatwick Park Hospital, specialising in gastrointestinal cancer and the early detection of bowel cancer, inflammatory bowel disease, capsule endoscopy, iron deficiency anaemia and reflux disease. He holds a PhD from University College London for studies into the diagnosis of gastro-oesophageal reflux disease (GORD), Barrett's oesophagus and the development of gastrointestinal cancer and their treatment. Dr Mackenzie is also a mentor within the National Bowel Cancer Screening Programme.