What is Vitamin B12?

Vitamin B12 (1) is a type of B vitamin, which is essential for our body to survive. It is also referred to as cobalamin. Vitamin B12 is needed to form red blood cells, form DNA, and plays a large role in the function and development of brain cells and nerve cells (1). It is naturally found in animal based foods such as meat poultry and fish, however it can also be fortified into foods such as cereal and sports drinks, and be supplemented into the diet.

What is Vitamin B12 Deficiency?

Vitamin B12 (2) deficiency, commonly referred to as folate deficiency anaemia, is when the body is not getting sufficient amounts of vitamin B12, so the body begins producing abnormally large red blood cells that don’t function as they are meant to. Those who are 65 (3) and older are more at risk of developing vitamin B12 deficiency as well as people who follow a vegan and vegetarian diet, or those who struggle with disordered eating.


It is easy for this vitamin deficiency to go unnoticed for some time as it can be hard to detect. Since B12 plays a large role in (3) producing red blood cells, keeping the nervous system healthy and creating the building blocks of all cells in our body, it is quite important that we notice the symptoms of a deficiency so we can fix it before more issues are caused!

Vitamin B12 deficiency could cause some of the following problems (3):

  • Abnormal lack of energy
  • Being lethargic
  • Pale appearance
  • Ulcers in the mouth
  • Always tired even when well rested
  • Vision issues
  • Weakness of your muscles
  • Brain fog / Confusion
  • Issues remembering things
  • Mild depression
  • Anxiety
  • Feelings of ‘pins and needles’

As many of these symptoms are common to other illnesses, please raise question with your health providers if you are experiencing any of the listed problems.


As there is a list of reasons one could be deficient in vitamin B12 these are a few of the most common (3):

Pernicious Anaemia (3)- This is an autoimmune disease, which attacks healthy cells in your body that prevents the absorption of B12 from digested food. In the UK this is the most common cause for vitamin B12 deficiency.

Dietary Habits (3) – A long term restrictive diet, disordered eating, or poor dietary habits can be the cause behind deficiency in many vitamins, one being vitamin B12. Aside poor or restrictive diets, those who follow plant-based, vegan, or vegetarian diets may also be at risk of B12 deficiency if not eating fortified foods or supplementing.

Medical Conditions (4) – Certain medical conditions such as atrophic gastritis, intestinal disorders, or celiac disease can put someone at higher risk of vitamin B12 deficiency.

Medications (3)– Different medications can lower B12 levels or heavily affect how much B12 your body absorbs. A few of these medications include metformin, proton pump inhibitors (PPI’s), antiepileptic drugs, chloramphenicol, as well as anticonvulsants.

Treating B12 Deficiency

Diet related:

Those who have been deemed deficient in vitamin B12 due to a lack of it in the diet have a few options for treatment. Those who eat animal products can begin to add foods high in B12 consciously into their diet daily until levels become normal again. Those who follow a plant-based, vegan, or vegetarian diet can look to implement foods fortified with B12 into their diet, however this may not be sufficient amounts, therefore supplementation may be necessary. If you or someone you know is struggling with getting enough vitamin B12 in their diet, speak to one of our expert dietitians for help!

Non-Diet Related:

Normally if your B12 deficiency is not due to a lack of the vitamin in your diet, the probable treatment is injection. Depending on your specific cause for deficiency or level of deficiency of B12, an injection of hydroxocobalamin every 2 to 3 months is usually sufficient to keep levels healthy. Those who require injection in the UK will likely be given hydroxocobalamin because it stays in the body for longer (5), however there is an alternative injection called cyanocobalamin.

Foods High in Vitamin B12

The NHS advises (6) that adults 19 to 64 have around 1.5 micrograms (1.5 ug) of vitamin B12 daily.

Animal Sources:

(per serving)

  • Clams: (84.1 ug)
  • Liver: (70.7ug)
  • Trout: (5.4 ug)
  • Salmon: (4.8 ug)
  • Tuna: (2.5 ug)
  • Beef: (1.4 ug)
  • Milk: (1.2 ug)
  • Yoghurt: (1.1 ug)
  • Cheese: (0.9 ug)
  • Eggs: (0.6 ug)
  • Chicken Breast: (0.3 ug)


(per serving)

  • Nutritional Yeast: (5 ug)
  • Marmite: (1.9 ug)
  • Fortified Tofu or Tempeh: (2-4 ug, varying on type – check label)
  • Fortified Breakfast Cereals: (1-5 ug varying on cereal)
  • Fortified Plant Milks: (0.5-2.0 ug varying on type)
  • Fortified Margarine Spreads: (0.2 ug)
  • Nori: (2 ug)
  • Fortified Dairy Free Yoghurt: (1.4 ug)
  • Fortified Fruit Juices: (1-2.5 ug varying on juice)

Written By: Faith Kinsley 08/05/2023

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1 – Mayo Clinic. (2021, July 17). Vitamin B-12. Retrieved from Mayo Clinic: https://www.mayoclinic.org/drugs-supplements-vitamin-b12/art-20363663

2 – NHS. (2023, February 20). Symptoms -Vitamin B12 or folate deficiency anaemia. Retrieved from NHS: https://www.nhs.uk/conditions/vitamin-b12-or-folate-deficiency-anaemia/symptoms/

3 – NHS. (2023, February 20). Overview -Vitamin B12 or folate deficiency anaemia. Retrieved from NHS: https://www.nhs.uk/conditions/vitamin-b12-or-folate-deficiency-anaemia/

4 – Wiginton, K. (2023, January 14). What Can Cause a B12 Deficiency? Retrieved from WebMD: https://www.webmd.com/diet/b12-deficiency-causes#:~:text=What%20Can%20Cause%20a%20B12%20Deficiency%3F%201%20Pernicious,Surgery%20…%206%20Vegan%20or%20Vegetarian%20Diet%20

5 – NHS. (2023, February 20).Treatment -Vitamin B12 or folate deficiency anaemia. Retrieved from NHS: https://www.nhs.uk/conditions/vitamin-b12-or-folate-deficiency-anaemia/treatment/

6 – NHS. (2020, August 3). B vitamins and folic acid. Retrieved from NHS: https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-b/#B12