Vitamin B12 is a water-soluble vitamin required for healthy red blood cell formation, DNA synthesis and normal development and function of the central nervous system.

Where vitamin B12 comes from

Vitamin B12 occurs naturally in animal-derived foods and is also added to some fortified foods. Supplements are another source. People who eat little or no animal food may need particular attention to reliable fortified foods or supplementation.

Vitamin B12 deficiency

Deficiency can occur because intake is inadequate or because the body has difficulty absorbing B12. Pernicious anaemia, some gastrointestinal conditions or surgery, and prolonged use of certain medicines can contribute.

Possible deficiency symptoms include fatigue, weakness, megaloblastic anaemia and neurological changes such as numbness or tingling. These symptoms are not specific to B12 deficiency, so symptoms alone cannot establish a diagnosis.

Testing and treatment

Blood testing is commonly used to assess B12 status, with additional testing sometimes needed when results are uncertain. Treatment depends on the cause and severity of deficiency.

Taking extra B12 when a person is already sufficient should not be presented as a proven way to boost energy, immunity, cognition or sleep. Anyone concerned about deficiency should discuss appropriate testing and treatment with a qualified healthcare professional.