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Vitamin B12 or folate deficiency anaemia: Symptoms and causes

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Besides an iron deficiency, a lack of vitamin B12 or folate (also known as vitamin B9 or folic acid) may also lead to anaemia. Though less common, a shortage in either one of these nutrients can produce abnormally large red blood cells unable to carry out their job effectively.

Red blood cells transport oxygen around the body via an important substance called haemoglobin. Anaemia arises when there are fewer red blood cells than average or insufficient haemoglobin in each red blood cell.

Both vitamin B12 and folate nutritional deficiencies tend to be more common in older people, affecting around one in 10 people aged 75 or older and one in 20 people aged 65 to 74 (1).

The sooner you can spot the signs of a vitamin B12 or folate deficiency, the sooner you can replace the missing vitamins with the right dietary changes, supplements, or injections.

What are the symptoms of vitamin B12 or folate deficiency anaemia?

Since vitamin B12 and folate play critical roles in the body, especially when it comes to the nervous system, a shortage of either can lead to various symptoms, as we outline below (2).

  • Extreme fatigue

  • Muscle weakness

  • Mouth ulcers

  • Distorted vision

  • A red, sore tongue

  • Pins and needles

  • Emotional health issues, including low mood and confusion

  • Experiencing difficulties with understanding, memory, and judgment

It’s also worth noting that you may experience some of these symptoms if you have vitamin B12 or folate deficiency, not anaemia.

What are the causes of vitamin B12 or folate deficiency?


Poor diet

A lack of dietary vitamin B12 or folic acid may lead to vitamin B12 or folate deficiency anaemia.
Since vitamin B12 is mainly found in animal foods, people who follow strict vegan diets are often thought to be more at risk of a vitamin B12 deficiency.


Nutritionally-unbalanced fad or ‘crash’ diets may also give rise to a vitamin B12 and folate deficiency.

Pernicious anaemia

Pernicious anaemia is an autoimmune condition that affects your stomach and may lead to a vitamin B12 or folate deficiency. The National Institute of Health and Care Excellence (NICE) reports that pernicious anaemia the most common cause of a vitamin B12 deficiency (3).

An autoimmune condition happens when the immune system – your natural defence system against infection and illness – attacks the body’s healthy cells. And when your immune system attacks the cells in your stomach, it can prevent your body from absorbing vitamin B12 and folic acid from the food you eat.

According to the Pernicious Anaemia Society, pernicious anaemia is often thought to be a disease that affects the elderly (4). And yet, a survey carried out by the same society revealed that pernicious anaemia could affect people of all ages.
Pernicious anaemia is also more prevalent in women, families, and those with other autoimmune conditions.

Certain medication

Medication that affects the body’s ability to absorb both vitamin B12 and folate, like anticonvulsants and proton pump inhibitors (PPIs), may contribute to a vitamin B12 or folate deficiency.


Digestive issues, such as coeliac disease and Crohn’s disease, can also prevent the body from absorbing vitamin B12 or folic acid. 


A developing baby can leach a mother’s folate stores to produce amino acids, red blood cells, DNA, and cells, which may lead to folate deficiency anaemia. Without enough folate in pregnancy, it may contribute to the development of congenital disabilities, such as neural tube abnormalities (spina bifida).

What are the risks of vitamin B12 or folate deficiency anaemia?

Although experiencing complications with vitamin B12 or folate deficiency anaemia is rare, it’s still best to be aware of them. They include:

  • Temporary infertility

  • Heart conditions

  • Pregnancy complications and congenital disabilities

  • Issues with the nervous system

More often than not, the right treatment can resolve these problems. However, complications with the nervous system may be permanent.

How to treat vitamin b12 or folate deficiency?      

As with iron-deficiency anaemia, treating vitamin B12 or foliate-deficiency anaemia is usually straightforward, and involves dietary improvements, supplements, and – in some instances – injections, to replenish your depleted nutritional stores. Learn more about the specific changes you need to make here.

If you have pernicious anaemia, on the other hand, you will typically need regular vitamin B12 injections.
To prevent neural tube abnormalities, all women are advised to 400µg of folic acid before conceiving and up until they’re 12 weeks pregnant.

Receiving a diagnosis is an extremely important first step in treating vitamin B12 or folate deficiency anaemia. Always see your GP if you suspect you may be a candidate. With an accurate and early diagnosis, you can easily reverse the condition and restore yourself to health.

To find out more about managing anaemia, head back to our dedicated health blog .


  1. 2021. Vitamin B12 or folate deficiency anaemia. [ONLINE] Available at: 
  2. 2021. Vitamin B12 or folate deficiency anaemia. [ONLINE] Available at: 
  3. 2021. Anaemia - B12 and folate deficiency CKS
  4. Pernicious Anaemia Society. 2021. Who is most at risk? href="!backgroundSub:2">https:#!backgroundSub:2">https:" > NICE. [ONLINE] Available at: 


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Disclaimer: The information presented by Nature's Best is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. Self-treatment is not recommended for life-threatening conditions that require medical treatment under a doctor's care. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications.

Our Author - Keri Filtness


Keri Filtness has worked in the Nutrition Industry for 19 years. She is regularly called upon for her professional comments on health and nutrition related news. Her opinions have been featured by BBC3, Prima, Vitality, The Mirror, Woman’s Own and Cycling Weekly, amongst others. She has also worked one to one with journalists, analysing their diets and health concerns and recommending changes and additions, where appropriate.

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