Vitamin B12 deficiency in over 16s: diagnosis and management

Context

Vitamin B12 deficiency is caused by a lack of the vitamin in the diet or problems with absorption from the gastrointestinal tract (for example, because of autoimmune gastritis or major gastric resection). Recreational nitrous oxide use can also cause a deficiency because the substance inactivates vitamin B12 in the body. Vitamin B12 deficiency can lead to a wide range of symptoms and complications, including mental health problems and neurological problems such as cognitive impairment. It is more common in older people and is thought to affect around 5% of people aged between 65 and 74 years and more than 10% of people aged 75 and over.

Vitamin B12 deficiency is usually diagnosed and treated in primary care. A blood test is usually done when people present with symptoms such as unexplained fatigue, which can be common in many conditions, or when there are abnormal findings on other blood tests. Testing is also done when investigating conditions such as anaemia, macrocytosis, and neuropsychiatric or neurodegenerative symptoms or signs.

Treatment for vitamin B12 deficiency depends on the cause but the aim is to replace vitamin B12 and improve the person's symptoms. The most common treatments are oral vitamin B12 replacement, or intramuscular injections given by a healthcare professional.

This guideline aims to improve the diagnosis and management of vitamin B12 deficiency, including deficiency caused by malabsorption (for example, linked to autoimmune gastritis or coeliac disease), the long-term use of some medications and diet. It also aims to reduce complications and improve quality of life for people with suspected and confirmed deficiency.