Iron deficiency anaemia: symptoms, causes, treatment and tests

Symptoms often build slowly, so people adapt without noticing. The NHS lists tiredness and lack of energy, shortness of breath, noticeable heartbeats, paler than usual skin and headaches. NICE CKS notes that signs such as pallor and atrophic glossitis (a smooth, sore tongue) are common, and that there may be no signs even in someone with severe anaemia.

There is also a group of less common symptoms in people who are not pregnant that the NHS lists, which can surprise people because they seem unrelated to blood.

• Ringing, buzzing or hissing sounds in the head (tinnitus).

• Food tasting strange, a sore tongue and painful sores at the corners of the mouth.

• Hair loss and spoon-shaped nails.

• Itching and restless legs syndrome.

• Difficulty swallowing.

• Craving non-food items such as paper or ice (pica).

Once the reason has been found, the GP recommends treatment for it. If the red cell count is low, the NHS says iron tablets will be recommended and need to be taken for about 6 months, and that drinking orange juice after a tablet may help absorption. NICE CKS describes one tablet once daily of ferrous sulfate, ferrous fumarate or ferrous gluconate, continued for 3 months after iron deficiency is corrected, with haemoglobin checked after 2 to 4 weeks. A rise of less than 20 g/L at that point is a reason for specialist assessment.

Side effects are common, and the NHS lists constipation or diarrhoea, tummy pain, heartburn, feeling sick and darker than usual poo. Taking the tablets with or soon after food may reduce them, and the NHS stresses the importance of continuing despite side effects, and of following the GP's instructions on how to take them.

For diet, the NHS suggests more dark green leafy vegetables, fortified cereals and bread, meat, dried fruit and pulses, and less tea, coffee, milk and dairy foods and foods high in phytic acid such as wholegrain cereals around the time iron is taken, as large amounts can reduce absorption.

The NHS says heavy periods and pregnancy are very common causes. In pregnancy it is most often due to too little iron in the diet. Bleeding in the stomach and intestines is another common cause, and the NHS lists regular use of anti-inflammatory painkillers such as ibuprofen and aspirin, stomach ulcers, inflammation of the bowel or oesophagus, piles, and less commonly cancers of the bowel or stomach.

NICE CKS also names malabsorption as a route to deficiency, and mentions coeliac disease when advising on a trial of iron treatment. Diet matters too, but the NHS says most people can get the iron they need from a varied diet, and the recommended daily amounts are 8.7mg for men aged 19 and over, 14.8mg for women aged 19 to 49 and 8.7mg for women aged 50 and over.

Iron is needed to make haemoglobin, the part of the red blood cell that carries oxygen around the body. When iron stores run low, red cell production falls. NICE CKS describes iron deficiency as arising from long-term negative iron balance, with a spectrum that runs from iron depletion through to iron deficiency anaemia, where the red cell count itself is reduced.

The NHS describes the cause simply as a lack of iron, often because of blood loss or pregnancy. NICE CKS adds that the cause is often multifactorial and can broadly be attributed to dietary deficiency, malabsorption, increased loss or increased requirements.

Iron deficiency can exist without anaemia, and anaemia can have other causes. That is why a diagnosis depends on blood results and a search for the reason behind them, not on symptoms alone.

A GP asks about lifestyle and medical history and usually arranges a full blood count (FBC) to check the red blood cell level. The NHS says no preparation is needed and that the test also looks for other types of anaemia. NICE CKS defines anaemia by haemoglobin below 130 g/L in men over 15, below 120 g/L in non-pregnant women over 15, and below 110 g/L in pregnancy, with a lower figure of 100 g/L after birth.

Serum ferritin is described by NICE CKS as the test that most reliably reflects total body iron stores, with a level below 30 micrograms/L confirming iron deficiency. It is harder to interpret with infection or inflammation and may be less reliable in pregnancy.

If the cause is unclear, the NHS says the GP may arrange a faecal immunochemical test (FIT) to look for blood in a stool sample or refer to a specialist. NICE CKS advises urgent suspected-cancer referral for people with iron deficiency anaemia and a FIT result of at least 10 micrograms of haemoglobin per gram of faeces, and gastroenterology referral for all men and postmenopausal women unless there is obvious non-gut bleeding. It also says a trial of iron without investigation should not be used for men and postmenopausal women.

The NHS says untreated iron deficiency anaemia makes you more at risk of illness and infection because iron affects the immune system, may increase the chance of heart or lung complications such as an abnormally fast heartbeat or heart failure, and carries a greater risk of problems before and after birth in pregnancy.

Repeat blood tests over the following months show whether iron is recovering. NICE CKS also recommends that premenopausal women under 50 with colon symptoms, a strong family history of gut cancer, persistent anaemia despite treatment or no periods are referred to gastroenterology, and that women with heavy periods unresponsive to medical treatment or with postmenopausal bleeding are referred to gynaecology.

The NHS advises seeing a GP if you think you might have iron deficiency anaemia. The NHS says that if the reason is not clear, the GP may arrange other tests, such as a faecal immunochemical test (FIT) to look for blood in a stool sample, or refer you to a specialist.

NICE Clinical Knowledge Summaries, written for clinicians, sets out when the cause is looked for more urgently. It says to refer urgently on a suspected cancer pathway if a FIT result is at least 10 micrograms of haemoglobin per gram of faeces, to refer all men and postmenopausal women with iron deficiency anaemia to gastroenterology unless there is obvious bleeding from somewhere other than the gut, and to investigate men with haemoglobin below 120 g/L and postmenopausal women below 100 g/L more urgently. It also says women with postmenopausal bleeding should be referred to gynaecology.

Iron tablets are dangerous to young children. The NHS says an overdose of iron in a young child can be fatal, so keep tablets out of reach and get urgent medical help if a child swallows them.

The NHS says women who lose a lot of blood in their periods are at higher risk of iron deficiency anaemia and may need iron supplements, and suggests speaking to a GP or registered dietitian. It says taking 17mg or less a day of iron supplements is unlikely to cause harm, but you should continue a higher dose if a GP advises it.

On the NHS, the first step is a GP appointment and a full blood count, usually followed by iron treatment and a search for the cause. Depending on the findings, the GP may arrange a FIT test or refer you to gastroenterology or gynaecology, as described above. The NHS says you might be referred to a specialist dietitian if you find it hard to include iron in your diet.

The same blood tests (full blood count and ferritin) can be arranged privately if you prefer. Whichever route you take, the NHS and NICE guidance above is clear that the reason for low iron needs to be found, so share results with your GP rather than simply starting supplements.