Vitamin B12 deficiency: what is it and what are the symptoms?

Victoria Lambert
B12 is necessary for healthy blood - Collection Mix: Subjects RM

Our bodies are remarkably adept at absorbing, storing and using vitamins and minerals. But sometimes our diet and lifestyle can make it more difficult to get enough of certain nutrients – which is where deficiency comes in.  

Lack of sunlight can lead to a deficiency in vitamin D, for example, which we need to build strong bones. And as you probably already know, low levels of fruit and vegetables in our daily diet can cause a shortage of vitamin C, which is crucial in keeping our immune systems healthy.

One of the vitamins which is most commonly associated with deficiencies is vitamin B12, which we need to maintain healthy blood and a healthy nervous system. It is estimated by the NHS that B12 deficiency affects around 1 in 10 people aged 75 or over, and 1 in 20 people aged 65 to 74. The symptoms of vitamin B12 deficiency can be physical or mental. 

Vitamin B12 is only found in animal products so vegetarians and vegans can find it difficult to source. To counter this, some foods are fortified with vitamin B and it is possible to take a daily supplement, but certain drugs such as Metformin (taken for diabetes) can also interfere with its absorption.

Here's everything you need to know about vitamin B12...

What is vitamin B12? 

Vitamin B12, sometimes called cobalamin, is one of eight B vitamins that have a vital role in keeping our bodies happy. B12 is water-soluble, meaning it cannot be stored in the fat cells in the body; any not used at once is flushed through the body.

What are the sources of vitamin B12?

Foods high in vitamin B12 include: shellfish such as oysters, clams and mussels; crabs; fish; beef; milk and yoghurt; eggs and fortified breakfast cereals.

How much Vitamin B12 is in one egg?

There's around 50 microgrammes of vitamin B12 in one large egg.

What are the benefits of vitamin B12? 

Vitamin B12 has an important role in the normal functioning of the brain and central nervous system as it helps with the formation of myelin, a fatty white substance crucial to the health of nerve cells, including neurotransmitters, the brain cells responsible for sending messages around the body. This means cobalamin is particularly essential during pregnancy to support the growth of the developing foetus.

It also helps with digestion and heart health, so a vitamin B12 deficiency can lead to both digestive disorders and an increased risk for heart disease. We need B12 to create healthy red blood cells too and to create DNA.

Deficiency in vitamin B12 has been linked to depression and poor mental health.

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What are the symptoms of vitamin B12 deficiency? 

Cobalamin deficiency symptoms include extreme tiredness, a lack of energy, pins and needles (paraesthesia), a sore and red tongue, mouth ulcers, muscle weakness, disturbed vision, psychological problems, which may include depression and confusion and problems with memory, understanding and judgement. One or more of these could indicate your vitamin B12 levels are too low.

As ever with medical matters, if you are worried you could be suffering from one or more of these symptoms, you are advised to make an appointment with your local GP who will test for B12 deficiency.

What causes vitamin B12 deficiency?

“There are a number of potential causes of vitamin B12 deficiency,” says Wai Ling Lo, Senior Clinical Pharmacist at The Princess Grace Hospital, part of HCA UK. “This reflects its relatively complex absorption process and the numerous potential sources of interference with this process.”

The most common cause is autoimmune disease pernicious anaemia, Lo explains, where the immune system attacks healthy cells in the stomach, preventing vitamin B12 being absorbed from food. “Non-immune disorders of the stomach or small intestine such as bariatric surgery, Crohn’s disease or coeliac disease can also interfere with vitamin B12 absorption,” she adds.

Lo points out that there are other risk factors for deficiency, including a decreased intake (due to reduced intake of animal products, a strict vegan diet or breastfeeding by a vitamin B12-deficient mother). Other autoimmune conditions such as thyroid disease or vitiligo may affect B12 levels, as can some rare genetic disorders.

She says: “Medications and drugs that interfere with absorption or stability such as metformin, histamine receptor antagonists, proton pump inhibitors and nitrous oxide can all have an impact.”

How is age a factor?

Older individuals, says Ms Lo, may have a combination of conditions that interfere with absorption of vitamin B12 from food, including inflammation of the stomach, reduced or halted production of stomach acid due to antacid use, intestinal bacterial overgrowth due to antibiotics, and/or excess alcohol.

“These individuals can adequately absorb crystalline vitamin B12 from supplements; thus, this condition is referred to as food cobalamin malabsorption. A similar phenomenon was reported in individuals infected with human immunodeficiency virus (HIV).”

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How is vitamin B12 treated?

If you are concerned about a deficiency, your GP can check your vitamin levels with a blood test. Treatment usually begins with a course of injections, one given every other day for two weeks or until symptoms improve. If deficiency is diet related, then you may be prescribed vitamin B12 tablets to take between meals or offered an additional injection every six months.

Improving or changing your diet can prevent it recurring. Vitamin B12 is found in meat, fish, eggs, dairy products, yeast extract (such as Marmite) and specially fortified foods.

But if the deficiency is not related to your diet, injections will be needed every three months for life.

Can you take too much vitamin B12?

There is insufficient evidence on the effects of large daily doses of vitamin B12, but taking less than 2mg per day in supplements is unlikely to do you any harm.