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Vitamin B12 deficiency

Vitamin B12 is important for the way the body works, and people who don't have enough of it may feel tired or have a lack of energy

Vitamin B12 helps in the production of healthy red blood cells that carry oxygen around the body.

Not having enough vitamin B12 is called vitamin B12 deficiency anaemia. This condition makes the body produce larger than normal red blood cells, described as megaloblastic or macrocytic, which don't do their job as well.

Once diagnosed, vitamin B12 deficiency can usually be treated successfully with B12 injections and sometimes with B12 tablets.

Symptoms of vitamin B12 deficiency

Anaemia and anaemia caused by a lack of vitamin B12 can result in symptoms which include:

  • Extreme tiredness or fatigue
  • A lack of energy or lethargy
  • Being out of breath
  • Feeling faint
  • Headache
  • Ringing in the ears ( tinnitus)
  • Lack of appetite

More specific symptoms linked to a lack of vitamin B12 include:

  • Yellowing of the skin
  • Sore, red tongue
  • Mouth ulcers
  • Changes or loss of some sense of touch
  • Feeling less pain
  • Walking problems
  • Vision problems
  • Mood changes, irritability, depression or psychosis
  • Symptoms of dementia

Causes of vitamin B12 deficiency

Vitamin B12 deficiency is more common in older people and affects around one in 10 over 75s.

The most common cause of vitamin B12 deficiency is pernicious anaemia, an auto-immune condition that affects around one in 10,000 people. Pernicious anaemia is caused by a lack of a protein called intrinsic factor that’s needed to absorb vitamin B12 from food into the body from the gastro-intestinal tract. This condition is more common in people over 60, in women, in people with a family history of pernicious anaemia or some autoimmune conditions, including Addison’s disease and vitiligo.

Vitamin B12 deficiency is risk for people who follow a strict vegan diet who don't eat the major food sources of B12: meat, eggs and dairy products. Babies whose mums are vegetarians may have vitamin B12 deficiency.
Other causes of vitamin B12 deficiency include:

  • Atrophic gastritis, or thinning of the stomach lining
  • Stomach ulcers
  • Surgery to remove part of the stomach or small intestine
  • Digestive conditions such as Crohn's disease, coeliac disease, bacterial growth or a parasite.
  • Medication, including proton pump inhibitors (PPIs) for indigestion.

Diagnosis of vitamin B12 deficiency

Blood tests and examination of blood cells under the microscope assess haemoglobin levels, the size of red blood cells and the level of vitamin B12 in the blood. The levels of folate are also usually checked for the related condition folate deficiency anaemia.

Once the diagnosis is confirmed, further tests may be carried out to try to find out what's causing the anaemia.

A referral may be made to a specialist, such as a haematologist for blood conditions, a gastroenterologist for digestive disorders or a dietitian for advice on eating food containing more vitamin B12.

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