Vitamin B12

Vitamin B12 is also called cobalamin and belongs to the group of B vitamins.

Vitamin B12 is needed to make new cells in your body including red blood cells. It's important for normal blood and nerve function. It also plays a part in making folate (vitamin B9).

Most people can get enough vitamin B12 from their diet. Vitamin B12 is found naturally in animal products including meat, chicken, fish, seafood, eggs, milk and other dairy foods such as cheese and yoghurt.

It may also be added to some processed foods such as breakfast cereals, plant-based milks, yeast spreads (eg, Marmite) and nutritional yeast products.

Here are the recommended dietary intakes (RDIs) of vitamin B12 for people of different age groups. The measurement for vitamin B12 is in micrograms, shown as this symbol 'µg'. You might also see it written as 'mcg'.

Getting enough vitamin B12 is especially important during pregnancy and breastfeeding when more vitamin B12 is needed.

• Babies (0 to 6 months): 0.4 µg
• Babies (7 to 12 months):  0.5 µg
• Children (1 to 3 years):  0.9 µg
• Children (4 to 8 years): 1.2 µg
• Children (9 to 13 years): 1.8 µg
• Adolescent (14 to 18 years): 2.4 µg
• Adult (19+ years): 2.4 µg
• Pregnant people: 2.6 µg
• Breastfeeding people: 2.8 µg

Vitamin B12 levels can be measured with a blood test.

• People with pernicious anaemia – which is an autoimmune condition where you're unable to absorb vitamin B12 from food. This is the most common cause of vitamin B12 deficiency.
• People with digestive conditions – such as Crohn’s disease, coeliac disease and atrophic gastritis (where the lining of the stomach is thinned).
• Following gastric surgery – where parts of the bowel including the stomach or end of the small intestine have been removed.
• Prolonged use of certain medicines – metformin or proton pump inhibitors (omeprazole, lansoprazole, pantoprazole).
• Older people – because your gut is less able to absorb B12 as you get older.
• People following a strict vegan or vegetarian diet – where animal products (source of vitamin B12) are reduced or excluded. Read more about being vegetarian or vegan.
• Chronic alcoholics – because of poor nutrition.

Most healthy adults don't need a vitamin B12 supplement.

However, if you're low in vitamin B12 because your body can’t absorb it from food, your doctor will prescribe an appropriate treatment which may include vitamin B12 injections or a high-dose vitamin B12 supplement. 

Eat a variety of foods and at most meals include meat, chicken, fish, eggs, cheese, yoghurt or milk.

If you eat a plant-based or vegan diet and need to include more B12 into your diet:

• Check the ingredients list and look for products where vitamin B12 has been added especially for foods you regularly eat.
• Choose a fortified breakfast cereal.
• Use a fortified plant-based milk daily for tea, coffee, smoothies, breakfast etc.
• Use a fortified yeast spread (eg, Marmite) as a toast topping or sandwich filling.
• Mix nutritional yeast into sauces, soups, mashed potato.
• Sprinkle nutritional yeast over salads, toast toppings etc.

Vitamin B12 deficiency may result in symptoms from anaemia and other symptoms related to the gut, brain and nervous system.

Symptoms may include:  

• feeling weak or tired
• rapid breathing or shortness of breath
• palpitations (uneven heartbeat)
• problems with vision
• problems with memory, understanding and judgment (cognitive changes)
• numbness
• muscle weakness
• pins and needles
• incontinence
• headaches
• indigestion
• loss of appetite
• diarrhoea
• a sore or red tongue, sometimes with mouth ulcers.

Treatment of vitamin B12 deficiency will depend on the cause. 

If you can't get enough vitamin B12 from your diet, a healthcare provider, such as a dietitian, can advise you on how to include more vitamin B12-containing foods. People following a vegan diet will need to increase intake of foods that have had B12 added including breakfast cereals, plant-based milk, nutritional yeast or yeast spreads, (eg, Marmite) and may need to take a vitamin B12 supplement.

If the deficiency is due to poor absorption from your gut, or pernicious anaemia, your healthcare provider may prescribe hydroxocobalamin, which is given as an injection into your buttock muscle. Read more about vitamin B12 supplements.