What is vitamin B12 and why do we need it?

Vitamins are vital for helping our body function and each one plays a different key role.


Vitamin B12 – also known as cobalamin, is a water-soluble vitamin that's naturally found in some foods, added to others and synthesised by bacteria in the small intestine. It is involved in many vital processes in the body, including:

  • Producing red blood cells
  • Keeping the nervous system healthy
  • Releasing energy from food
  • Creating DNA and RNA (the building blocks of every cell in the body)

Check out our Vitamins and Minerals Information Hub to learn more about key nutrients – from whether you’re getting enough vitamin D to the top 10 healthiest sources of vitamin C, plus vital minerals you need in your diet.


The benefits of vitamin B12 include:

  • Produces red blood cells
  • Prevents a blood condition called megaloblastic anaemia
  • May support bone health
  • May improve your mood and mental health
  • May be a good energy boost

How much vitamin B12 do you need each day?

Vitamin B12 is necessary in only very small amounts each day. The NHS advise adults consume 1.5 micrograms (mcg) per day.

What are the symptoms of a vitamin B12 deficiency?

Vitamin B12 deficiency is quite hard to detect and can go undiagnosed for some time. Symptoms can include fatigue, lethargy, shortness of breath, pale skin, mouth ulcers, sensations of 'pins and needles', disturbed vision, impaired mental function and depression. Many of these symptoms are not unique to vitamin B12 deficiency, and not everyone who is diagnosed will experience them.

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A more severe form of vitamin B12 deficiency is called pernicious anaemia. This is an autoimmune disease which occurs due to issues with a specific glycoprotein called intrinsic factor (IF), which is created in the stomach and necessary to absorb vitamin B12. Pernicious anaemia causes the immune system to attack the cells in the stomach that produce IF. Without IF, vitamin B12 cannot be absorbed and therefore deficiency can occur.

Read more from the NHS about vitamin B12 or folate deficiency anaemia and pernicious anaemia.

Who might be at risk of a vitamin B12 deficiency?

If you are unable to enjoy a varied and balanced diet or your digestion is compromised – for example, you have a medical condition such as coeliac disease, Crohn's disease or you are elderly – you may be at higher risk of low levels of vitamin B12.

Strict vegans who do not take vitamin B12 supplements or include two to three servings of fortified foods in their diet daily are also at increased risk of deficiency. Likewise, vegetarians who do not regularly include dairy or eggs in their diet. If you are pregnant and are concerned that you may be at risk of low vitamin B12 levels, refer to your GP, because low levels may increase your baby’s risk of a neural defect.

Those on certain prescribed medications, such as the long-term use of antacids, may also be at risk of lower vitamin B12 levels.

What are the food sources of vitamin B12?

Vitamin B12 is mainly found in the following:

  • Meat
  • Offal
  • Milk/dairy
  • Fish
  • Eggs
  • Liver
  • Clams
  • Kidney
  • Oysters
  • Nutritional yeasts

Other foods rich in vitamin B12 with their recommended doses include:

  • 100g mussels = 10.6mcg
  • 100g lamb liver = 83mcg
  • 100g mackerel = 9.1mcg
  • 100ml soya milk (fortified) = 0.4mcg
  • 100g yogurt = 0.4mcg

For vegetarians and vegans, it is harder to obtain this vitamin, although it is found in some fermented foods, such as tempeh and more commonly in nori. Alternatively, look out for vegan and vegetarian foods that are fortified with vitamin B12; these include nutritional yeast, plant milks, spreads and breakfast cereals.

There is some evidence to suggest that the form of B12 found in vegetarian/vegan sources is not as bio-available as that from animal sources. If you follow a plant-focussed diet and are concerned about your vitamin B12 status, speak to your GP or dietitian for guidance – they may recommend you have a blood test.


If you are concerned about your vitamin B12 status, contact your GP or dietitian before embarking on a supplementary intervention or making significant changes to your existing diet or medication protocol.

Recipes that are rich in vitamin B12

Liver & bacon with onion gravy
Warm mackerel & beetroot salad
Vegan tomato & mushroom pancakes
Mussels with tomato and chilli
Vegan kale pesto pasta
Sauteéd liver & apple salad with blackberry dressing
Steak & kidney pudding
Devilled cheek & kidney pot pie
Lamb's liver & mash
Lamb's liver & onions

Enjoyed this? Now read:

What supplements should I take?
Top 10 healthiest sources of vitamin C
Am I getting enough vitamin D?
What are B vitamins?
Vital vitamins

This content was updated on 18th October 2023.

Kerry Torrens is a qualified Nutritionist (MBANT) with a post graduate diploma in Personalised Nutrition & Nutritional Therapy. She is a member of the British Association for Nutrition and Lifestyle Medicine (BANT) and a member of the Guild of Food Writers. Over the last 15 years she has been a contributing author to a number of nutritional and cookery publications including BBC Good Food.

Jo Lewin is a registered nutritionist (RNutr) with the Association for Nutrition with a specialism in public health. Follow her on Twitter @nutri_jo.


All health content on bbcgoodfood.com is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other healthcare professional. If you have any concerns about your general health, you should contact your local healthcare provider. See our website terms and conditions for more information.

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