HealthInfo Waitaha Canterbury
Vitamin B12 deficiency & pernicious anaemia
Te mimititanga huaora B12 me te mate waihanga pūtau toto whero
Being low in vitamin B12 can cause serious problems as it's needed to make red blood cells that carry oxygen around your body. It also helps your nerves and brain.
Most people get vitamin B12 from animal foods such as eggs, dairy, meat and seafood. It isn't found in fruit and vegetables. You also need a protein called intrinsic factor in your stomach to be able to get the vitamin B12 into your blood.
People at risk of vitamin B12 deficiency include:
- vegans
- breastfed infants of vegan mothers – these babies can develop anaemia within months of being born because they have not had enough time to store vitamin B12 in their bodies
- older people and others who have a poor appetite and eat very small meals
- people with digestive conditions such as Crohn's disease and coeliac disease.
Causes of vitamin B12 deficiency
The commonest cause of vitamin B12 deficiency is a condition called pernicious anaemia. It's an autoimmune condition that causes antibodies from your own immune system to attack the cells in your stomach that make a protein called intrinsic factor. This means your body can’t absorb vitamin B12. We do not know why this happens.
Pernicious anaemia usually develops in people aged over 50. Women are more often affected than men and it tends to run in families. It occurs more often in people who have other autoimmune diseases.
Other things that can cause low vitamin B12 include:
- digestive conditions such as Crohn's disease and coeliac disease
- surgery to remove your stomach or the last part of your small bowel
- some medicines that affect the absorption of vitamin B12, including metformin and heartburn medicines such as omeprazole and pantoprazole
- not getting enough vitamin B12 from your food, for example from having a strict vegan diet.
Symptoms of vitamin B12 deficiency
If you have low red blood cells such as in pernicious anaemia, you might:
- feel tired and faint, be breathless, look pale and feel your heart thumping (palpitations)
- have a sore tongue or mouth ulcers
- get pins and needles or numbness
- have vision problems
- feel unsteady
- experience depression, confusion or memory problems.
Severe or long-lasting pernicious anaemia can damage your heart, brain and other organs. It can also cause other problems, such as nerve damage, memory loss and gut problems. You may also have a higher risk for weakened bone strength and stomach cancer.
See your general practice team if you have the symptoms listed above.
Treating vitamin B12 deficiency
You can help yourself by choosing good food sources of vitamin B12, such as:
- meat, chicken, seafood and eggs
- cow's milk and milk products such as yoghurt, cheese and ice cream
- foods fortified with vitamin B12, such as some soy, almond, oat and rice milks and some yeast extracts such as Marmite.
If you have mild vitamin B12 deficiency, you may be able to increase your levels by taking vitamin B12 or vitamin B complex supplements. These aren't free on prescription, but you can buy them from some pharmacies and supermarkets. You'll need at least 50 mcg (micrograms) of Vitamin B12 a day.
If you have more serious vitamin B12 deficiency, you'll need vitamin B12 injections to replace, then keep up your body stores of vitamin B12. If you have pernicious anaemia, you'll need these injections every two to three months for the rest of your life.
HealthInfo recommends the following pages
- Patient.info – Pernicious anaemia and vitamin B12 deficiency
A factsheet on vitamin B12 deficiency anaemia, a condition where vitamin B12 cannot be absorbed into your body.
On the next page: Eating well to prevent vitamin B12 deficiency
Written by HealthInfo clinical advisers. Last reviewed February 2023.
SourcesReview key: HIANA-16978
