---
title: "Vitamin B12 deficiency: Symptoms & Treatment | HealthAnswers"
description: "A plain-English guide to vitamin B12 deficiency — symptoms, causes and treatment."
url: https://healthanswers.co.uk/conditions/vitamin-b12-deficiency/
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---

# Vitamin B12 deficiency: Symptoms & Treatment | HealthAnswers

Health A–Z

A plain-English guide to vitamin B12 deficiency — symptoms, causes and treatment.

Written by HealthAnswers editorial team Medically reviewed by [HealthAnswers UK doctor review panel](https://healthanswers.co.uk/our-doctors/) Reviewed 3 July 2026

## 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.

## Who is this page for?

This page is for people in the UK who want a plain-English overview of Vitamin B12 deficiency, including when to seek help and what NHS care usually involves. It explains general information, not what is wrong with you personally.

## Who should skip this page?

Skip this page if you need a diagnosis, a prescription, or emergency care. It cannot replace a GP, pharmacist, NHS 111 or 999. If you are in immediate danger, call 999; for urgent advice that is not life-threatening, call 111 in England, Scotland or Wales, or use your GP out-of-hours service in Northern Ireland.

On this page 5 sections

## Key facts about vitamin b12 deficiency

- B12 is essential for healthy red blood cells and nerves.
- Deficiency causes tiredness, pins and needles, and other varied symptoms.
- It is diagnosed with a simple blood test.
- Treatment with tablets or injections is effective — earlier is better.

## 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.

## ! When to see a GP about vitamin b12 deficiency

See a GP if you have persistent tiredness, pins and needles, a sore or red tongue, low mood, or memory problems — a blood test can check your B12. Don't self-treat with supplements before testing, as this can mask the diagnosis. See a GP **promptly** for worsening numbness, weakness or balance problems, because nerve symptoms recover best when treated early.

## Common questions about vitamin b12 deficiency

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.

## Sources

- [NHS — Vitamin B12 or folate deficiency anaemia](https://www.nhs.uk/conditions/vitamin-b12-or-folate-deficiency-anaemia/)