What is Vitamin B12?

Vitamin B12 is part of the B complex of vitamins alongside vitamin B9 (folic acid). They are essential vitamins, however the body is unable to make them itself and so instead must take them in through the diet. Vitamin B12 is required for the formation of red blood cells as well as for forming a coat around nerve cells called myelin.[1]

What Role/s Does It Play in The Body?

Vitamin B12 plays a key role in several physiological functions. It is needed for the maturation of red blood cells, if it is not present then this can lead to pernicious anaemia which can have neurological side effects.[2]  

Vitamin B12 is also required for cell metabolism and function, so deficiency can have detrimental effects on the body’s organ systems. Deficiency can be subtle and non-specific which can make diagnosis difficult.[2]

The body can store vitamin B12 which means deficiency may occur over a prolonged period.[3] The body can store up to 5mg of vitamin B12 and as the UK government recommends a daily intake of 1.5 micrograms per day, depleting these stores can take several years.[4]

How Does Vitamin B12 Affect My Wellbeing?

Vitamin B12 can only be derived from animal sources such as meat, fish and dairy. Therefore, deficiency can be common amongst the vegan and/or vegetarian community. It can also be present in pregnant women as their requirements will increase. Older people are also susceptible possibly due to poor nutrition. Some of the symptoms of vitamin B12 deficiency include:

  • Fatigue
  • Anaemia
  • Neurological features
  • Sore tongue
  • Bone marrow suppression
  • Cardiomyopathy

Usually, folate is also analysed alongside vitamin B12 as these can both be markers for macrocytic anaemias (where red cells are larger than they should be and have a reduced oxygen carrying capacity). They can also both be used to look at nutritional status especially if malnutrition is suspected. Both B vitamins are needed for adequate red cell development, cell repair and DNA synthesis.

High levels of vitamin B12 are not usually observed but may be seen with leukaemia or liver dysfunction.

How Can I Improve My Result?

Vitamin B12 can only be acquired from the diet and so this may be the best place to start with improving and maintaining B12 levels. Supplementation may be required particularly during pregnancy.


As vitamin B12 is found in foods derived from animal sources you should incorporate these into your diet. Good sources include:

  • Liver
  • Beef
  • Clams
  • Trout
  • Salmon
  • Cheese
  • Milk
  • Yoghurt
  • Eggs
  • Chicken

If you cannot eat meat, then vitamin B12 supplementation may be required to ensure you have enough in your body for it to function appropriately.[5]

If your diet is high in vitamin C this can also limit the normal absorption of vitamin B12. Therefore, you should keep your intake of vitamin C within normal parameters and perhaps consume it separately to vitamin B12 where appropriate.[1]


Exercise is believed to be key to managing stress and reducing anxiety and depression.[6] You should aim to exercise for 30-60 minutes most days of the week to feel the full benefits of exercise.

However, you should bear in mind that anaemia can seriously affect your energy levels. Therefore, you may find that your performance may be affected if you are anaemic


You can track your Vitamin B12 level through a simple at home finger prick blood test.

[1] The Open University. (2017). Nutrition: Vitamins and Minerals. The Open University.

[2] Peters, P and Schaefer, C. (2007). Vitamins, Minerals and Trace Elements. In: Drugs During Pregnancy and Lactation, 2nd ed.

[3] Institute of Medicine (US). (1998). Standing Committee on the Scientific Evaluation of Dietary Reference Intakes and its Panel on Folate, Other B Vitamins, and Choline. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington (DC): National Academies Press (US); N, Estimation of the Period Covered by Vitamin B12 Stores.

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

[5] National Institutes of Health. (2018). Vitamin B12. Available at: https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/#h3

[6] Harvard Health Publishing Harvard Medical School. (2011). Exercising to Relax. Available at: https://www.health.harvard.edu/staying-healthy/exercising-to-relax