Red Blood Cell (RBC)

What Are They?

Red blood cells are made in the bone marrow and are fundamental in transporting oxygen from the lungs to the cells. A red blood cell count determines how many red blood cells are in circulation.[1]

Which tests include this marker?

What Role/s Red Blood Cells Have in The Body?

Red blood cells are the most common type of blood cell in circulation. Their main function is to distribute oxygen around the body via the protein, haemoglobin. They also carry carbon dioxide, which is a waste product, from the cells to the lungs where it can be exhaled and removed from the body entirely.

Red blood cells have no nucleus which means they have a greater surface area and this enhances their ability to transport oxygen. They are a biconcave disc shape with a depressed centre. The normal size of a red blood cell is between 6 and 8 µm (micrometres) and have a thickness of 2 µm.

A red blood cell count can be used to diagnose many blood-related disorders. Women naturally tend to have a lower red cell count than men, while levels will naturally decrease with age in both genders. If the level is more than 10% below the normal value then the person can be classed as anaemic.

How Do Red Blood Cells Affect My Wellbeing?

A low red blood cell count often indicates the presence of anaemia. Anaemia can be caused by various factors including nutritional deficiencies such as vitamin B12.

Vitamin B12 Deficiency
Vitamin B12 is needed in the production of DNA and for cell metabolism. Thus, if there is a deficiency in this essential vitamin, then it can have serious clinical consequences. We get our B12 from our diet, but it is only found in animal-derived products. Therefore, deficiency is common in vegetarians and vegans. Our body storage of vitamin B12 is relatively high, so it can take a few years for these stores to be depleted and for deficiency to occur. The symptoms of vitamin B12 deficiency are: 

  • Fatigue
  • Sore tongue
  • Shortness of breath
  • Neurological features e.g. confusion, forgetfulness, loss of balance, psychosis
  • Pale skin
  • Heart palpitations

It is not possible to prevent the occurrence of vitamin B12 deficiency in some cases. However, if it is caused by malnutrition or poor diet then it is possible that with some changes vitamin B12 deficiency could be kept at bay.[2]

Folate Deficiency
Another nutritional deficiency which may result in a low red cell count is folate deficiency. The condition is like vitamin B12, except the deficiency is caused by a lack of folate. The symptoms are very similar between the two types of anaemia.  Human beings must get their intake of folate from the diet as we are unable to make it ourselves. Folate is particularly important during pregnancy and is needed for adequate foetal and placental development.[3] All females are advised to take 400 micrograms of folic acid while they try to get pregnant and then for the first 12 weeks of pregnancy. This helps to ensure the baby’s spine develops properly and reduces the risk of neural tube defects including spina bifida.[4]

Other reasons for a low red cell count include:

  • Bleeding
  • Kidney disease
  • Bone marrow failure possibly caused by a tumour or from radiation therapy

A high red cell count can indicate congenital heart disease, dehydration, chronic obstructive lung disease or the over-production of red cells by the bone marrow. 

How Can I Improve My Result?

Red blood cells and their components are highly valuable in the human body. Their transportation of oxygen around the body is vital to carry out the metabolic processes required to sustain life. Our lifestyle can have major impact on the health of our red cells. For example, chronic obstructive pulmonary disease is a treatable and preventable disease which is characterised by a progressive airflow obstruction. The development of the disease is linked to an abnormal inflammatory response by the lungs to toxic particles or gases i.e. smoking. Therefore, by not smoking or giving up your risk of COPD could be reduced. COPD is linked with a high red cell count.[5] 


Iron is fundamental to the health and efficiency of red blood cells. There are two types: haem and non-haem. Haem iron is found in foods which are animal derived such as red meat, liver, fish and poultry. Non-haem iron, however, is found in plants like green leafy vegetables, seeds, pulses and nuts. Some companies also fortify their products with iron usually this includes breakfast cereals, bread and milk/dairy products. Women are more susceptible to iron deficiency due to the iron lost during their menstrual cycle. Therefore, it is essential to increase the amount of iron they eat, particularly before and during a menstrual bleed.[6] 

You should also make sure you are adequately hydrated at all times. Dehydration can result in a high red cell count.

Vitamin B12 also needs to be consumed through the diet. However, it is normally found in animal-based products, including: 

  • Eggs
  • Milk
  • Fish
  • Poultry
  • Meat
  • Shellfish

Therefore, for some groups, it may be necessary to supplement. Vitamin B12 deficiency is common in elderly people who are often reliant on a ‘tea and toast’ diet.


Exercise is an important aspect of a healthy lifestyle. Regular exercise can help to increase blood flow to muscles which enables oxygen to reach the tissues. Exercise also helps to increase the oxygen-carrying capacity of red blood cells.[7]

Tests that include this marker

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[1] National Health Service. (2015). Red Blood Cell Count. Available at:

[2] Hunt, A., Harrington. D and Robinson, S. (2014). Vitamin B12 Deficiency. BMJ: 349.

[3] Castaño, E., Piñuñuri, R., Hirsch, S and Ronco, A, M. (2016). Folate and Pregnancy, Current Concepts. It is Required Folic Acid Supplementation? Rev Chil Pediatr: 88(2), pp 199-206.

[4] NHS Choices. (2018). Why Do I Need Folic Acid in Pregnancy? Available at:

[5] Littner, M, R. (2011). In the Clinic: Chronic Obstructive Pulmonary Disease. Annals of Internal Medicine. Available at:

[6] Coad, J and Pedley, K. (2014). Iron Deficiency and Iron Deficiency Anaemia in Women. Scandinavian Journal of Clinical and Laboratory Investigation: 74.

[7] Mairbäurl, H. (2013). Red Blood ells in Sports: Effects of Exercise and Training on Oxygen Supply by Red Blood Cells. Frontiers in Physiology: 4.

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