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Anaemia - how to diagnose and treat

Anaemia: Causes, Symptoms and Treatment

Blood is coloured red because of the iron contained in the molecule haemoglobin.


Haemoglobin is held inside the red blood cells and its job is to carry oxygen around the body. Anaemia is diagnosed when either the number of red blood cells, or the amount of haemoglobin that they contain, is too low.


The cells of our body need oxygen to use the fuel that provides energy for all the body’s functions. If you suffer with anaemia, then your body can’t effectively get oxygen to where it needs to go, and therefore the symptoms of anaemia are basically the symptoms of lacking energy. This means that people with anaemia suffer with shortness of breath, tiredness, weakness, lightheadedness and, in severe cases, chest pain because the heart itself is not getting enough oxygen. Sufferers may also be pale because they lack the haemoglobin that gives them a healthy colour.


There are many causes of anaemia, but they fall into two broad categories; either the body is not making enough blood, or too much blood is being lost.


Making Blood

Sometimes the body can’t make enough blood because it lacks the basic ingredients it requires. Iron is needed to make haemoglobin so, if iron levels are low (iron deficiency), haemoglobin levels soon follow. Similarly, vitamin B12 and folic acid are important for making blood, and deficiencies in these micronutrients can also result in anaemia. Because plant-based diets may contain fewer sources of B12 and iron, we sometimes see anaemia in people who follow them.


The vast majority of blood cells are made in the bone marrow, so if the bone marrow is not working then the body won’t produce enough blood. There are a number of causes for this including viral infections, medications, toxins, autoimmune disorders, radiotherapy, and chemotherapy. Anaemia may therefore complicate a variety of illnesses and the treatment for some illnesses.


The kidneys are also important for making red blood cells because they produce a hormone called erythropoietin which stimulates the bone marrow to produce red blood cells. You may have heard of erythropoietin as the medication ‘EPO’ which some doping athletes use to cheat their way to a higher blood count. Kidney disease can therefore also cause anaemia because of the underproduction of erythropoietin.

Tests we offer for diagnosing Anaemia

Losing Blood

The most obvious way to lose blood is through bleeding. This bleeding may be dramatic, such as following a traumatic injury or a big operation, or it may be more mundane. Perhaps the most common cause of anaemia amongst women of child-bearing age is the blood loss that occurs during periods, particularly if periods are heavy. Blood loss may be more insidious; small amounts of blood may be lost continually in the bowel or urinary tract. Blood loss like this might come from a relatively harmless cause, such as wear and tear changes in the bowel or haemorrhoids, but if we find evidence of bleeding in these places, we normally exclude sinister causes such as bowel or bladder cancer.


Sometimes blood cells are destroyed more quickly than they are produced which causes a steady decline in the total number of red blood cells. This is known as haemolytic anaemia and can be caused by autoimmune conditions, medications, and severe infections. It can also occur in inherited conditions such as thalassemia or sickle cell disease. In sickle cell disease, for example, the red blood cells are sickle shaped instead of being round, and this causes them to be damaged as they squeeze through blood vessels.


Diagnosing Anaemia

Diagnosing anaemia is very straightforward. The ‘Full Blood Count (FBC)’ blood test is one of the most commonly requested blood tests in medical practice and it tells us about haemoglobin levels, the number of red blood cells, and how much haemoglobin those red blood cells contain. It therefore tells us immediately whether there is anaemia or not.

Working out why there is anaemia can be more difficult, although the FBC may give us a clue. One of the parameters in the FBC is the Mean Cell Volume, which is a measurement of the average size of the red blood cells. The cells are small (a low MCV) in iron deficiency and in thalassemia. The cells are large (a high MCV) with vitamin B12 or folate deficiency, and may also be large in thyroid disease, alcohol abuse and some other blood disorders.


If the haemoglobin is low and there is an abnormal MCV, this narrows down the number of extra tests we need to do to work out the cause. If the MCV is normal then we need to think about the other causes of anaemia such as chronic kidney disease, or inflammatory and autoimmune conditions.

Treating Anaemia

Treatment of anaemia depends on the cause of the anaemia and the severity of the anaemia. It may be as simple as taking iron or vitamin supplements, or may be as dramatic as an urgent blood transfusion. In between there are intravenous iron infusions, B12 injections, or injections of EPO. Of course, the underlying cause must also be addressed and the treatment of this will be different for each cause. Once the anaemia is corrected, people tend to feel much better.

Diagnosing Anaemia blood tests

Limitations of Full Blood Count in diagnosing anaemia

The Full Blood Count (FBC) test is a commonly used diagnostic test that provides important information about the number and type of cells in the blood, including red blood cells, white blood cells, and platelets. However, despite its usefulness, the FBC test has some limitations in diagnosing anaemia, which include:

  1. Insufficient Information: An FBC test provides information about the number and type of cells in the blood, but it does not provide information about the function of these cells. Therefore, additional tests, such as a ferritin test or iron studies, may be needed to diagnose the specific type of anaemia and determine the underlying cause.

  2. False Negative Results: In some cases, an FBC test may show normal results even in the presence of anaemia. This can occur if the person has a mild form of anaemia, or if the person has a condition that affects the production of red blood cells. 

  3. False Positive Results: An FBC test may show elevated levels of red blood cells even if the person does not have anaemia. This can occur if the person has a condition that affects the volume of fluid in the blood, such as dehydration, or if the person is taking certain medications, such as steroids. Therefore, the results of an FBC test must be interpreted in the context of the person's overall health and medical history.

  4. Interference from Other Factors: The results of an FBC test can be influenced by factors such as age, sex, and race, and can also be affected by certain medications, such as blood thinners. Therefore, the results of an FBC test must be interpreted in the context of the person's overall health and medical history.

  5. Variability of Results: The results of an FBC test can vary depending on the laboratory that performs the test, and different laboratories may use different methods and reference ranges. Therefore, it is important to have the test performed at the same laboratory each time, to ensure that results are comparable.

Despite these limitations, the FBC test is still a valuable diagnostic tool and is often used in combination with other tests to diagnose anaemia and evaluate a person's overall health. It is important to interpret the results of the FBC test in conjunction with the person's symptoms, medical history, and other relevant test results.

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