Quick answer
What is vitamin b12 deficiency?
Vitamin B12 deficiency means the body lacks a vitamin essential for healthy blood and nerves. It can cause tiredness, pins and needles, a sore tongue, low mood and memory problems. It is diagnosed with a blood test and treated effectively with B12 tablets or injections — and it matters to treat it early.
What is vitamin B12 deficiency?
Vitamin B12 is essential for making healthy red blood cells and keeping the nervous system working. A deficiency develops when the body cannot absorb enough B12 or the diet does not supply it. It is common — particularly in older people — and very treatable, but it deserves to be caught early because of its effects on the nerves.
Symptoms
B12 deficiency develops gradually and its symptoms are varied:
- tiredness, lethargy and breathlessness
- pins and needles
- a sore, red or smooth tongue, or mouth ulcers
- muscle weakness
- low mood, irritability
- problems with memory, concentration or balance
What causes it
The most common cause is pernicious anaemia, an autoimmune condition that stops the gut absorbing B12. Other causes include a diet lacking B12 — it comes from meat, fish, eggs and dairy, so vegans need fortified foods or supplements — certain medicines, and gut conditions or surgery affecting absorption.
Diagnosis and treatment
A simple blood test makes the diagnosis. Treatment depends on the cause: if absorption is the problem, B12 injections (often lifelong) restore levels; if diet is the cause, high-dose tablets and dietary changes are usually enough. It is best not to self-treat with supplements before testing, as this can mask the diagnosis.
Why early treatment matters
Blood-related symptoms recover fully with treatment. Nerve-related symptoms — numbness, weakness, balance trouble — also usually improve, but can become permanent if the deficiency is left untreated for a long time. Worsening nerve symptoms are a reason to see a GP promptly, not to wait.
Common questions
- What are the symptoms of B12 deficiency?
- They are varied — tiredness and lack of energy, pins and needles, a sore or red tongue, mouth ulcers, muscle weakness, low mood, and problems with memory or concentration. Symptoms often develop gradually.
- What causes B12 deficiency?
- The most common cause is pernicious anaemia, where the body cannot absorb B12 properly. Other causes include a diet low in B12 (it is found in meat, fish, eggs and dairy — vegans need fortified foods or supplements), some medicines, and gut conditions or surgery affecting absorption.
- How is it treated?
- With B12 injections or high-dose tablets, depending on the cause. If absorption is the problem, injections — often lifelong — are usually needed. If diet is the cause, supplements and dietary changes can be enough.
- Why does early treatment matter?
- B12 deficiency can affect the nerves, causing numbness, weakness and balance problems. These nerve symptoms can become permanent if deficiency goes untreated for a long time, while blood-related symptoms usually recover fully.