Vitamin B12 deficiency: symptoms, causes, treatment and recovery

The NHS says vitamin B12 and folate keep the nervous system healthy, among other functions, and that a deficiency in either can cause a wide range of problems. Symptoms tend to develop gradually, and not everyone has all of them.

The NHS also says some of these problems can happen if you have a deficiency but do not have anaemia, and that symptoms must be taken into account alongside blood tests. Some people have symptoms and seem to have normal levels, and some have low levels without symptoms.

• Extreme tiredness and a lack of energy.

• Pins and needles.

• A sore and red tongue, and mouth ulcers.

• Muscle weakness.

• Problems with your vision.

• Psychological problems, which can range from mild depression or anxiety to confusion and dementia.

• Problems with memory, understanding and judgement.

Vitamin B12 is involved in making red blood cells, keeping the nervous system healthy, releasing energy from food and using folate, according to the NHS. When too little is available, red blood cells can grow abnormally large and work poorly, a pattern called vitamin B12 deficiency anaemia. The same NHS page notes that some of the problems can also occur when B12 is low but you are not anaemic, so a normal blood count does not rule it out.

The body can store B12 for a while, which is one reason that deficiency often creeps up over months or years and symptoms are easy to mistake for ageing, stress or overwork.

The NHS says B12 deficiency anaemia is usually treated with injections of hydroxocobalamin, given every other day at first by a GP or nurse. What happens next depends on the cause. If the deficiency is diet-related, you may be advised to take B12 tablets daily between meals, or to have a hydroxocobalamin injection twice a year. People who struggle to get enough B12 from food, such as those following a vegan diet, may need tablets for life, while someone whose deficiency came from a prolonged poor diet may be able to stop once levels and diet have recovered.

If the deficiency is not diet-related, as in pernicious anaemia, you usually need an injection of hydroxocobalamin every 2 to 3 months for the rest of your life. If you have had neurological symptoms such as numbness or tingling in the hands and feet, you will be referred to a haematologist and may need injections every 2 months. The NHS says hydroxocobalamin is preferred to cyanocobalamin in the UK because it stays in the body for longer.

Monitoring is simple. A blood test is often done around 7 to 10 days after starting treatment, and another after about 8 weeks to confirm it has worked. Most people do not need further monitoring unless symptoms return or treatment is ineffective.

Pernicious anaemia is the most common cause of B12 deficiency in the UK. In this autoimmune condition the immune system attacks healthy cells in the stomach, which stops the body absorbing B12 from the food you eat. Because the problem is absorption rather than intake, eating more B12-rich food does not fix it.

Diet can also be responsible, though the NHS calls this uncommon. It can happen with a vegan diet if B12 supplements or fortified foods are not used, or after a restrictive or poor diet over a long time. Certain medicines, including anticonvulsants and proton pump inhibitors, can affect how much B12 the body absorbs. The NHS vitamin pages add that B12 is not found naturally in fruit, vegetables and grains, so vegans may not get enough. Older people are more affected, with roughly 1 in 10 people aged 75 or over having B12 or folate deficiency.

A GP can often make the diagnosis from your symptoms and blood tests. The NHS says the tests check haemoglobin level, whether red blood cells are larger than normal, and the levels of B12 and folate. It stresses that symptoms must be weighed alongside results, because some people have symptoms with seemingly normal levels, and some have low levels without symptoms.

If B12 deficiency is confirmed, further tests may look for the cause. These can include blood tests for pernicious anaemia, which the NHS says are not always conclusive but often give a good idea. Referral may go to a haematologist if the cause is uncertain, you are pregnant, or symptoms suggest nerve involvement; to a gastroenterologist if poor absorption by the gut is suspected; and to a dietitian if poor diet is the likely cause.

The NHS says good sources of vitamin B12 include meat, fish (salmon and cod), milk and other dairy products, cheese and eggs, and some fortified breakfast cereals. Vegetarians and vegans can look for foods fortified with B12, such as some yeast extracts, breakfast cereals and soy products, and should check the nutrition labels.

Adults aged 19 to 64 need about 1.5 micrograms a day, according to the NHS. It says that if you eat meat, fish or dairy foods you should be able to get enough from your diet, but that as B12 is not found naturally in foods such as fruit, vegetables and grains, vegans may not get enough.

The NHS says there is not enough evidence to show what the effects may be of taking high doses of B12 supplements each day, and that taking 2mg or less a day in supplements is unlikely to cause any harm. Eating more B12 does not fix pernicious anaemia, because the problem is absorption rather than intake.

Although uncommon, the NHS says B12 or folate deficiency, with or without anaemia, can lead to nerve problems, temporary infertility, heart conditions, and pregnancy complications and birth defects. Severe anaemia in adults can contribute to heart failure. Some complications improve with treatment, but nervous system problems can sometimes be permanent, which is why the NHS advises seeing a GP promptly if you think you may be deficient.

Folate deficiency can look similar, and the two are often considered together. The NHS says folic acid tablets are used for folate deficiency, usually for about 4 months. Before starting them, your GP will check your B12 level, because folic acid can improve symptoms so much that it masks an underlying B12 deficiency. If B12 deficiency is missed it could affect the nervous system.

The NHS says to see a GP if you think you may have a vitamin B12 or folate deficiency. These conditions can often be diagnosed from your symptoms and a blood test, and it is important to be diagnosed and treated as soon as possible because some problems can be irreversible.

The NHS says you will be referred to a haematologist if you have neurological symptoms such as numbness or tingling in the hands and feet caused by B12 deficiency, if your GP is uncertain of the cause, or if you are pregnant. Do not start or stop B12 treatment without medical advice.

Diagnosis and treatment are normally handled in primary care, with the district nurse or practice nurse giving injections. Private GPs and clinics can order the same blood tests, and some offer B12 injections, but the sensible questions are the same: what is the cause, what level was measured and how will the schedule be reviewed. Avoid starting supplements before testing if you can, since tablets can alter blood results.

Be wary of treatment schedules that are not linked to a diagnosed cause. The NHS pathway is built around identifying why B12 is low, because that decides whether treatment is short-term or lifelong.