HealthInfo West Coast-Te Tai Poutini
Vitamin B12 deficiency & pernicious anaemia
Being low in vitamin B12 can cause serious problems as it is 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 food such as eggs, dairy and meat. It's not 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 haven't had enough time to store vitamin B12 in their bodies
- older adults or others who may not get enough nutrients from the food they eat
- 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 your intrinsic factor so your body can’t absorb vitamin B12. We don't 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 parts of your bowel
- some medicines that affect the absorption of vitamin B12, including metformin and proton pump inhibitors
- 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 may be at higher risk for weakened bone strength and stomach cancer.
See your doctor if you have the symptoms listed above.
Treating vitamin B12 deficiency
You will need vitamin B12 injections to replace, then keep up your body stores of vitamin B12. If you have pernicious anaemia, you will need these injections every two to three months for the rest of your life.
You can also help yourself by choosing good food sources of vitamin B12, such as:
- meat, chicken, seafood and eggs
- milk and milk products such as yoghurt, cheese and ice cream
- foods fortified with vitamin B12, such as some soy, almond and rice milks, and some yeast extracts such as Marmite.
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. Endorsed by clinical director, Haematology Department, Canterbury DHB. Last reviewed May 2020.
Review key: HIANA-16978
