Vitamin B12 is a nutrient that helps keep your body’s blood and nerve cells healthy. A lack of vitamin B12 can lead to a condition called vitamin B12 deficiency anaemia.
In some cases, B12 deficiency is caused by pernicious anaemia, an autoimmune condition where the body can’t absorb B12 properly.
Vitamin B12 deficiency is usually treatable with supplements, either as tablets or injections, depending on the cause.
Symptoms of vitamin deficiency B12
- Feel unusually tired with a lack of energy
- Pins and needles (paraesthesia)
- A sore, red tongue
- Mouth ulcers
- Muscle weakness
- Vision problems
- Problems with memory, understanding, or judgment (especially in older adults)
- Depression or mood changes
- Pale or yellowing skin
Causes of Vitamin B12 Deficiency
Vitamin B12 deficiency can be caused by:
- Dietary deficiency – not getting enough B12 from food (common in vegan or vegetarian diets)
- Pernicious anaemia – where the immune system attacks cells in the stomach that produce intrinsic factor, a protein needed to absorb B12
- Digestive conditions – such as Crohn’s disease or coeliac disease
- Certain medicines – such as metformin or proton pump inhibitors
- Older age – where absorption of B12 from food becomes less efficient
Intrinsic Factor and Pernicious Anaemia
Intrinsic factor is a protein made in the stomach that helps your body absorb vitamin B12.
In people with pernicious anaemia, the body produces antibodies that attack the cells that make intrinsic factor. Without intrinsic factor, vitamin B12 cannot be absorbed properly, even if you are eating enough of it.
A blood test can check for intrinsic factor antibodies to help diagnose pernicious anaemia.
Test and Diagnosis
Your GP may arrange blood tests to check:
- Your vitamin B12 levels
- Your full blood count
- Whether you have intrinsic factor antibodies
These tests help to confirm the deficiency and identify the cause.
Treatment
Treatment depends on the cause of the deficiency.
If You Can Absorb B12 (no intrinsic factor antibodies found):
- You will likely be prescribed vitamin B12 tablets to take daily.
- These are effective and safe for long-term use.
If You Cannot Absorb B12 (intrinsic factor antibodies found / pernicious anaemia):
- You will need vitamin B12 injections, usually given every 2–3 months.
- These bypass the gut and deliver B12 directly into the bloodstream.
Treatment may be lifelong in the case of pernicious anaemia
Changing from Injections to Oral Treatment
Some patients currently receiving B12 injections may be offered a switch to oral tablets. This is based on updated clinical guidance and individual test results.
Why the Change?
- If your blood tests show no intrinsic factor antibodies, your body can absorb B12 naturally.
In this case, oral tablets work just as well as injections
Benefits to switching to tablets
- No need for regular appointments
- Easier and more convenient to manage
- Same effectiveness in maintaining B12 levels
Preventing Vitamin B12 Deficiency
- You may be able to prevent B12 deficiency by:
- Eating B12-rich foods like meat, fish, dairy, and eggs
- Taking a B12 supplement if you follow a vegan or restricted diet
- Regular monitoring if you have conditions that affect absorption