What is pernicious anaemia?
Pernicious anaemia is an autoimmune condition where your immune system mistakenly attacks cells in your stomach. These cells are responsible for producing a protein called intrinsic factor — helps your body absorb vitamin B12.
If you’re not producing enough intrinsic factor, your body can’t absorb vitamin B12 and it leads to a deficiency. This means your body can’t make enough red blood cells or each blood cell doesn’t have enough haemoglobin — anaemia.
Pernicious anaemia is the most common cause of vitamin B12 deficiency in the UK.
What does vitamin B12 do?
Vitamin B12 is essential for a healthy brain and nervous system. It’s also needed for making red blood cells — which are important for your energy levels.
If you’re deficient, common symptoms include:
- tiredness
- weakness
- pins and needles
- heart palpitations
- shortness of breath
- headaches
- difficulty concentrating


How to measure your vitamin B12 levels
You can measure your vitamin B12 levels with a blood test. If you’re getting vitamin B12 injections to treat pernicious anaemia, you can also check if your levels are improving.
An active vitamin B12 test is the best way to measure your levels — this is the amount of vitamin B12 your body can actually use. Active B12 represents 10-30% of the total B12 in your blood.
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Jane has pernicious anaemia and has been getting vitamin B12 injections to increase her levels. She's been monitoring if they're improving with a home blood test kit.
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