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Iron deficiency anaemia
What is iron deficiency anaemia?
Iron deficiency anaemia is a condition in which a person has too few red blood cells, caused by low levels of iron in the body. The body needs adequate levels of iron for the production of haemoglobin in red blood cells, which is the component of blood that transports oxygen through the body and gives blood its characteristic red colour. If there is a shortage of iron in the body, the bone marrow produces less red blood cells, which are also smaller in size. As a result of their reduced number and size, these red blood cells carry less oxygen to tissues, which leads to the symptoms of anaemia.
Iron in the body
Iron is typically absorbed by the gastrointestinal tract, which consists of a membrane-lined series of organs extending from the mouth to the anus through which food passes during digestion. The iron is then carried in the blood to the liver, where it can be stored or moved onto the bone marrow to form haemoglobin within red blood cells. The body then recycles the iron from old and worn-out red blood cells to make new ones.
Blood loss is the most common cause of iron deficiency anaemia. It might not always be obvious, such as when it occurs due to trauma, surgery or in women with heavy menstrual bleeding. For example, slow bleeding of the gastrointestinal tract in some circumstances is not visible and can often go unnoticed.
Decreased iron absorption
A less common cause of iron deficiency anaemia is decreased iron absorption. However, if the gastrointestinal tract is inflamed, or if you have a condition such as coeliac disease, you might not absorb enough iron, which can lead to iron deficiency anaemia.
A lack of iron-rich food in developing countries is a cause of iron deficiency anaemia in these places. In contrast, many developed countries have food with added iron. However, if you are vegetarian or if you do not eat enough red meat, you may not get all the iron you need, due to the fact iron is not as readily absorbed from plants as it is from meat.
If you are pregnant, your iron requirements are greater and if your intake is inadequate, you might develop iron deficiency anaemia.
Some of the risk factors for developing iron deficiency anaemia include:
Signs and symptoms
Sometimes, people with iron deficiency anaemia have no symptoms. When they do, common symptoms include:
- Shortness of breath, and;
- A rapid heart rate.
Other symptoms that are not as common include:
Methods for diagnosis
Because there are many potential causes of iron deficiency anaemia, a full history needs to be taken and physical examination performed by your doctor to identify the most likely cause of iron deficiency or blood loss. Relevant investigations will be performed according to your individual circumstances.
Full blood count
Using your blood sample, the number of red blood cells (erythrocytes), white blood cells (leukocytes) and platelets (thrombocytes) will be assessed.
This test assesses the size, shape and colour of red blood cells under a microscope. In iron deficiency anaemia, the red blood cells are typically small (microcytic), lacking in colour (hypochromic) and fewer in number than in healthy blood samples.
Other blood tests
Your blood will also be tested for iron levels and related proteins, such as ferritin, which help in the storage of iron.
The gastrointestinal tract can be a source of a wide range of conditions that cause iron deficiency anaemia so is often the focus of investigation if another cause is not obvious. Even if another cause, such as heavy menstrual periods, is present, your doctor may still wish to evaluate your tract to ensure you are not suffering with a concurrent cause.
Iron deficiency anaemia of unknown cause may be caused by 'occult' (hidden) bleeding or malabsorption from the gastrointestinal tract. Investigations may include:
Further blood tests may be performed to investigate for inflammation, coeliac disease or other deficiencies, such as vitamin B12 or folate, that may occur if the bowel is generally not absorbing substances well.
Faecal occult blood test
A faecal occult blood test (FOBT) detects blood in your faeces. It is most commonly used as a screening test for bowel cancer, but bleeding could be due to other causes. You will need to provide two samples on separate occasions, as bleeding can occur intermittently. FOBT may be helpful to detect if there is any bleeding from the gastrointestinal tract but may in some cases have false negatives. Further testing of the tract is often carried out even if you have a negative FOBT.
A colonoscopy is used to examine the length of the colon (large bowel). Before the procedure, your bowel will be prepared using an oral laxative solution and sometimes an enema washout. You can also help prepare your bowel by not eating but drinking plenty of clear fluids in the 12-24 hours prior. During a colonoscopy, a long tube with a camera called a colonoscope is inserted into your bowel through the anus. Air will be pumped into your colon to allow your doctor to see it properly. This procedure can help diagnose conditions of the bowel such as diverticular disease, bowel cancer and Crohn's disease that may be causing blood loss.
During an upper endoscopy you'll be sedated and a long, narrow, telescopic camera will be gently fed down the oesophagus and into your upper digestive system. Ulcers, cancers or inflammation of the oesophagus, stomach or small bowel may be seen. Biopsies may be taken to look for inflammation, infection or coeliac disease. All of these conditions can lead to iron deficiency anaemia.
Other gastrointestinal tract procedures
In some circumstances, where the cause of bleeding is not found with gastroscopy or colonoscopy, the remainder of the small bowel may need to be examined. Wireless capsule endoscopy may be used, in which a small capsular camera is swallowed and passes through the entire length of the bowel recording the bowel's appearance. Other investigations may include a small bowel follow-through, or radionuclide scanning, depending on your circumstances.
Types of treatment
Ideally, treatment of the underlying cause of iron deficiency or blood loss aims to correct the deficiency and anaemia. Sometimes oral or intravenous supplementation of iron is required, depending on the cause and/or severity of your iron deficiency anaemia.
Oral iron supplements come in a few different forms. Types of oral iron include ferrous fumarate, ferrous gluconate and ferrous sulphate in tablet or liquid form. It is generally recommended that people with an iron deficiency need 100 to 200 mg of elemental iron per day. Be sure to discuss dosage with your doctor, as the amount of the ferrous salts can be different to the level of elemental iron in the preparation. For example, a 325 mg ferrous sulphate tablet contains 105 mg of elemental iron. Taking too much iron can be dangerous for the body.
Taking iron tablets with food, calcium supplements, antibiotics, or drinks other than water (especially milk products) reduces the absorption of iron. Taking iron tablets with vitamin C tablets or orange juice increases the absorption of iron, because iron is best absorbed in an acidic environment.
Slow release polymer-coated iron tablets are not used to treat iron deficiency, as iron is best absorbed in the first part of the intestine and their coating means they are not absorbed until too far down the tract.
Parenteral iron (iron infusion)
If you cannot tolerate oral iron supplements, or your gastrointestinal tract is unable to properly absorb iron, then iron can be given as an infusion into the veins (intravenous).
Blood transfusions involve the administering of packed red blood cells into your bloodstream. Usually one or two units are required in people with iron deficiency anaemia. Each unit contains roughly 200 mg of iron. There are certain risks with blood transfusions, so these are generally reserved for those with very low red blood counts.
Treatment side effects
Side effects of oral iron include nausea, constipation and vomiting. These side effects can be reduced by lowering the iron dose, or taking the liquid form of ferrous sulphate and adjusting the amount you take. Iron also turns your stool very dark, almost black in colour. This is expected and is not a problem.
Children under six years of age are at risk of iron poisoning, so it is important to keep your iron tablets out of their reach.
Side effects of parenteral iron include itching, heart palpitations and dizziness. Iron dextran is a type of parenteral iron that can cause allergic reactions, which can be life-threatening. Non-dextran forms of parenteral iron, such as iron sucrose and ferric gluconate complex, carry much less risk and are used for that reason. Iron infusions are carried out under medical supervision in case of any adverse reactions.
The most common side effects of a blood transfusion are mild shortness of breath, fever and chills. Rare side effects include incompatibility reactions and infection with hepatitis C virus or HIV. However, rigorous blood donor screening and blood testing makes these extremely rare in Australia.
Iron deficiency anaemia leaves you feeling lethargic and unproductive, making it difficult to stay awake or exert energy on activities such as exercise.
Heightened risk of infection
Iron deficiency anaemia weakens your immune system, making you more likely to become ill as a result of infection.
Heart and lung problems
If the anaemia is severe, you are at risk of developing heart and lung complications such as a fast heart rate or heart failure.
If you are pregnant and have severe anaemia, it can increase the chances of your baby being born prematurely, having a low birth weight, having problems with their iron levels and poor performance in mental aptitude tests later in life. You are at risk of the same complications otherwise experienced in iron deficiency anaemia and can have an increased risk of developing postnatal depression.
Restless leg syndrome
Restless leg syndrome is thought to sometimes result from iron deficiency anaemia. It is a common condition that affects the nervous system, resulting in unpleasant sensations in your legs such as itching, tiredness, soreness or twitching, and an associated compelling need to move your legs. It is usually experienced when trying to sleep, but can occur during the day when symptoms are generally less noticeable.
Treatment continues until your red blood counts return to normal. You may still need to take iron supplements for a period of time after this to restore your iron stores. Some people do not respond to oral iron, in which case further testing is required to find out why. However, it may simply be that they were wrongly using slow-release iron tablets, or that they were not taking them as prescribed by their doctor.
Eating a balanced diet usually provides you with enough iron to meet your body's needs. Most of the time iron supplements will not be needed, as increasing dietary iron is enough to maintain iron stores.
If you have had iron deficiency before, you are at increased risk of getting it again, so daily iron supplementation, as prescribed by your doctor, may be used to prevent iron deficiency anaemia from returning. It is important to consult your doctor first, otherwise you risk an iron overdose.