High RDW: what does it mean?

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We know that the world of acronyms can be a bit complex and confusing at times, especially if they refer to an English term and the letters of the acronym do not match the Spanish translation. So if you ever go to the doctor and they tell you that you have a high RDW, this article will help you understand exactly what they mean.

First of all: RDW stands for red cell blood distribution width.i.e. erythrocyte distribution breadth test. It is indeed an analysis, to put it another way, in which blood, once again, is the protagonist. Thanks to it and its examination we can detect any kind of unevenness in its components and understand what is happening to the patient. This also makes the treatment much quicker and more concrete, which is what we are always looking for.

What is RDW?

Even if we have translated it, it is normal that it is not understood what an RDW is. This is, to put it in a more understandable way, a haemogram or complete blood count. This test is used to measure the number, composition and proportions of cellular components of the blood.

Although the acronym may not ring a bell, the RDW is one of the most basic tests for the in primary care and can help the physician to detect a large number of organic irregularities or pathologies even before symptoms develop in the patient. This particular analysis helps to assess the The red blood cells, the cells that carry oxygen from the lungs to the rest of the body.

The RDW, therefore, is part of or within what is a hemogram. and analyses both the production of blood cells and the patient’s general state of health. It is an excellent tool for detecting anaemia if the doctor sees any signs that could lead him or her to think about this problem. This is one of the most commonly requested scenarios, especially if accompanied by symptoms such as dizziness, tiredness or pale skin, among others.

However, the physician will also request an RDW when the patient has or has had an RDW:

  • Family history of blood disorders.
  • Bleeding during surgery or after a blow.
  • Have or have had a disease that can cause alterations in the blood cells.
  • Chronic diseases (such as HIV).

There is also the possibility that this test may be requested in a routine blood test, without there being any specific cause for it.

The values that appear when performing an RDW analysis have normal, high and low levels. These indicate the size of the red blood cells: if they are normal, their size is standard, if they are high, they are larger than normal, and if they are low, they are too small. When the analysis is received, the doctor will be in charge of reading the results, expressed in percentages. The standard value ranges from 11% to 14%.. Values below or above indicate that something is not working properly and therefore the cause of the problem should be sought and remedied.

The RDW as such does not require any prior preparation for its realisation. However, an 8-hour fast is usually carried out The blood test is usually performed together with the blood count, which does require fasting. In any case, it is best to follow the doctor’s instructions for taking a blood sample (maximum 5 minutes) on the spot by health professionals through a vein.

Although RDW is primarily used to distinguish between different types of anaemia, it is nowadays an analysis that is also used to determine the outcome and mortality in patients with heart failure, making it a very useful tool.

RDW high

Let us now look at the reason for this article: a patient is considered to have a high RDW, as we can deduce from the normal values, if it exceeds 15%.. This result suggests that there is an irregularity in the size of the red blood cells, so it is necessary to observe what is happening in the red blood cells. cause. Some of the most frequent are:

  • Iron deficiency anaemia. It is due to an iron deficiency that causes haemoglobin not to be synthesised correctly. In this case haemoglobin levels would be low and MCV decreased.
  • Megaloblastic anaemia. In this case, the cause of this disease is a deficiency of folic acid or vitamin B12. Our body needs these elements to synthesise the DNA in the precursors of these cells. The haemoglobin in this case would also be low and the MCV high, which is common in this disease.
  • Thalassemias. This is a series of genetic disorders in which abnormal forms of haemoglobin are synthesised. Both haemoglobin and MCV would have low values.
  • Liver disease. This organ regulates most of the chemical levels in the blood and also has the function of eliminating waste substances. If there is a problem that hinders their missions, the size of the red blood cells is often affected.

In addition to the causes, it has been shown that high RDW can help in the detection of other chronic diseases. (type 2 diabetes, cardiovascular pathologies such as heart failure, cancer…). Although there is currently no concrete and specific treatment to combat high RDW, we can change our lifestyle habits to favour the restructuring of levels. We’ll explain them below, so read on!

Let us now take a closer look at what the RDWalto blood values mean, as the same treatment will not have to be followed if it is slightly elevated or excessive:

  • Slightly elevated levels. It comprises a percentage in adults of 14.5 to 18 %. These results are generally not cause for alarm, especially if this is the only parameter that is above normal. The cause of this small increase may be an infection (which will go away with proper treatment), strenuous exercise or taking certain medications. Microcytic anaemia (low MCV and haemoglobin) may indicate iron deficiency anaemia.
  • Moderately high levels. It ranges from 18-26 % in adults and these levels may be indicative of severe iron deficiency anaemias, although they are more characteristic of megaloblastic anaemias (lack of vitamin B12 or folic acid). Low haemoglobin and high MCV would appear as a result.
  • Excessively high levels. Includes any value exceeding 26 %. In this case we would be dealing with sideroblastic anaemias due to a massive increase in the size of red blood cells. It can also occur if haemoglobin is extremely low in deficiency anaemias such as iron deficiency anaemia (low MCV) and in megaloblastic anaemias (high MCV). However, another cause of these excessive values may be the existence of 2 distinct red blood cell populations. This usually occurs when the patient is undergoing treatment for iron deficiency anaemia or megaloblastic anaemia, where red blood cell values can exceed 30%. But there is no cause for alarm: these results, in this case, indicate a positive response to treatment. Remember that if you have had a blood transfusion, values may also increase, so it is important to follow up routinely and consult a doctor whenever in doubt.

How to lower high RDW

As mentioned above, there is no single drug that can be used to treat the There is no immediate cure for elevated red blood cell values, but rather intervention on the underlying cause. It all depends on the person’s medical history and physical condition. That is why it is so important that, in the event of such an outcome, some changes in the patient’s daily habits. Here are some tips:

  • Regular physical exercise (does not need to be intense).
  • Sleep between 7 and 9 hours a day.
  • Avoid tobacco and alcohol consumption.
  • Increase consumption of foods rich in iron, vitamin B9 or vitamin B12. The doctor will indicate the diet to be followed, but it is important to prioritise foods containing these elements.


It is just as important to know the cause of high values as it is to know the cause of below-average values. Normally no disease or pathology associated with a low RDWespecially if the rest of the parameters analysed are OK. In this case, there is no need to worry, but it is advisable to analyse the reason for this decrease, since there are occasions in which it can indicate the existence of some disease.

Low RDW is also called Isocitosis and occurs when anaemia is caused by chronic disease (liver pathologies, kidney problems, HIV, cancer or diabetes).). In addition to RDW, MCV or mean corpuscular volume also tends to have low values.

When doubts and fears arise, the best thing to do is to go to a health centre and explain the problem so that your doctor can start investigating and can give you the most appropriate solution. That’s why testing and analysis is so important, and that’s what we do here at Ambar Lab. We have both a clinical laboratory as well as R&D collaborations.

Our services range from the performance of laboratory diagnostic tests to the development of new projects and advice on laboratory management issues. If you have any questions just contact us at contact our team so that they can help you find the specific solutions you need.

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