Vitamin B12 is part of the B complex of vitamins alongside vitamin B9 or folate. They are essential vitamins, so 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.
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.
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.
The body can store vitamin B12 which means deficiency may occur over a prolonged period. 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.
All these tests include Active B12. Select the test that suits your personal needs.
Because vitamin B12 plays such a crucial role in the maturation of red blood cells, low levels can have wide-ranging effects on the body which develop gradually over time. Some of the symptoms of B12 deficiency include:
If you have any of these symptoms then a blood test will confirm if it’s related to B12 deficiency and your GP will advise the best course of treatment.
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.
As mentioned above, vitamin B12 is an essential vitamin gained through the food we eat, so the best way to maintain good B12 levels is to eat more food that contains this vitamin. However, if your levels are very low, you may be recommended a vitamin B12 supplement.
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.
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.
Exercise does not directly impact your levels of B12, however, as part of a healthy lifestyle, you should be doing around 120 minutes of exercise per week.
 The Open University. (2017). Nutrition: Vitamins and Minerals. The Open University.
 Peters, P and Schaefer, C. (2007). Vitamins, Minerals and Trace Elements. In: Drugs During Pregnancy and Lactation, 2nd ed.
 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.
 Hunt, A., Harrington, D and Robinson, S. (2014). Vitamin B12 Deficiency. BMJ: 349.
 National Institutes of Health. (2018). Vitamin B12. Available at: https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/#h3