Vitamin B12 is an essential nutrient that helps keep your red blood cells healthy, supports normal brain and nerve function, and contributes to energy production. When your body doesn't get enough vitamin B12—or can't absorb it properly—you may develop a deficiency that can affect your physical and mental wellbeing.
Because vitamin B12 deficiency symptoms often develop gradually, they're easy to overlook or mistake for stress, ageing, or simply feeling run down. Recognising the early warning signs and seeking treatment promptly can help prevent more serious complications.
In this guide, we'll explain the common symptoms of vitamin B12 deficiency, what causes it, who's most at risk, and when you should seek medical advice.
Vitamin B12 Deficiency at a Glance
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Question |
Answer |
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Most common symptom |
Persistent tiredness or fatigue |
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Other symptoms |
Pins and needles, numbness, memory problems, sore tongue, low mood |
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Who is most at risk? |
Older adults, vegans, vegetarians, and people with digestive conditions |
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How is it diagnosed? |
Usually with a blood test |
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Can it be treated? |
Yes, with dietary changes, supplements, or injections depending on the cause |
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When should you see a GP? |
If symptoms are persistent, worsening, or affecting your daily life |
Key Takeaways
- Vitamin B12 is essential for healthy red blood cells, nerve function, and DNA production.
- Fatigue is often one of the earliest symptoms of vitamin B12 deficiency.
- Untreated deficiency can lead to nerve damage and neurological problems.
- Older adults, vegans, and people with digestive disorders are at greater risk.
- Early diagnosis and treatment can help prevent long-term complications.
What Is Vitamin B12 and Why Is It Important?
Vitamin B12 (also called cobalamin) is a water-soluble vitamin that plays several essential roles in the body.
It helps:
- Produce healthy red blood cells.
- Support normal brain and nervous system function.
- Contribute to DNA production.
- Support normal energy-yielding metabolism by helping your body release energy from food
Unlike some vitamins, your body cannot make vitamin B12 itself. It must come from your diet or supplements.
Good dietary sources of vitamin B12 include meat, fish, eggs, dairy products, and fortified foods such as some breakfast cereals and plant-based milks.
Without enough vitamin B12, your body may produce fewer healthy red blood cells, which can lead to vitamin B12 deficiency anaemia. This reduces the amount of oxygen carried around the body and is one of the main reasons why people with a deficiency often experience fatigue, weakness, and shortness of breath.
If your intake is too low or your body struggles to absorb vitamin B12, your stores can gradually become depleted, leading to deficiency.
Common Vitamin B12 Deficiency Symptoms
Vitamin B12 deficiency can affect several parts of the body. Some people may have low vitamin B12 levels without experiencing obvious symptoms, which is why blood tests are sometimes needed to confirm a deficiency.
While symptoms vary from person to person, they usually fall into three main categories.
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Physical Symptoms
One of the earliest and most common symptoms is persistent fatigue because your body may struggle to produce enough healthy red blood cells.
Other physical symptoms include:
- Weakness
- Pale or slightly yellow skin
- Shortness of breath
- Headaches
- Heart palpitations
- Loss of appetite
- Indigestion
- Unexplained weight loss
- A sore, red, or swollen tongue
- Mouth ulcers
- Nausea, vomiting, diarrhoea
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Neurological Symptoms
Vitamin B12 is essential for healthy nerves. If the deficiency continues untreated, it may begin affecting your nervous system.
Symptoms can include:
- Tingling sensation or pins and needles in the hands or feet
- Numbness
- Muscle weakness
- Difficulty with balance or coordination
- Vision changes
These symptoms should always be assessed by a healthcare professional, as prolonged deficiency can sometimes lead to permanent nerve damage.
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Cognitive and Mental Health Symptoms
Vitamin B12 deficiency can also affect your mood and thinking.
Some people experience:
- Memory problems
- Difficulty concentrating (brain fog)
- Confusion
- Low mood or depression
- Anxiety
- Irritability
These symptoms can have many causes, but vitamin B12 deficiency is one possibility your GP may investigate.
What Causes Vitamin B12 Deficiency?
Vitamin B12 deficiency develops when you don't get enough vitamin B12 or your body cannot absorb it properly.
Common causes include:
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Not Eating Enough Vitamin B12
People following vegan diets—and some vegetarians—may not consume enough vitamin B12 unless they eat fortified foods or take supplements.
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Pernicious Anaemia
This autoimmune condition prevents the body from absorbing vitamin B12 properly and is one of the most common medical causes of deficiency in the UK.
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Digestive Conditions
Conditions affecting the stomach or intestines can reduce vitamin B12 absorption, including:
- Crohn's disease
- Coeliac disease
- Chronic gastritis
People who have had stomach or bowel surgery may also be at increased risk.
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Certain Medications
Long-term use of some medicines may lower vitamin B12 levels, including:
- Metformin
- Proton pump inhibitors (PPIs)
- Some acid-reducing medicines
If you take these medications for an extended period, your GP may recommend monitoring your vitamin B12 levels.
Who Is Most at Risk?
Anyone can develop a vitamin B12 deficiency, but it's more common in:
- Adults aged 60 and over
- Vegans and some vegetarians
- People with Crohn's disease or coeliac disease
- Individuals with pernicious anaemia
- People who've had stomach or intestinal surgery
- Those taking long-term metformin or acid-reducing medication
- People with low dietary intake during pregnancy or breastfeeding (who should seek advice from their healthcare professional)
If you fall into one of these groups and have symptoms, it's worth speaking to your GP about whether testing is appropriate.
When Should You See a GP?
If you have ongoing symptoms such as persistent tiredness, pins and needles, or memory problems, it's worth speaking to your GP. Vitamin B12 deficiency can often be confirmed with a blood test.
Getting diagnosed and treated early gives you the best chance of a full recovery. Although many symptoms improve with treatment, leaving the deficiency untreated for too long may lead to permanent nerve damage or other lasting complications.
How Is Vitamin B12 Deficiency Diagnosed?
Your GP will ask about your symptoms, medical history, diet, and any medications you're taking.
If vitamin B12 deficiency is suspected, you'll usually have a blood test to measure your vitamin B12 levels. Depending on the results, additional blood tests may be needed to identify the underlying cause or rule out other conditions with similar symptoms.
Identifying the cause is essential, as some people require long-term treatment if their body cannot absorb vitamin B12 properly.
Some symptoms of vitamin B12 deficiency are similar to those of folate deficiency, which is why your GP may test for both.
How Is Vitamin B12 Deficiency Treated?
Treatment depends on what's causing the deficiency and how severe it is.
Your GP may recommend:
- Vitamin B12 tablets if the deficiency is related to diet.
- Vitamin B12 injections if your body cannot absorb the vitamin effectively, such as in pernicious anaemia.
- Dietary changes to include more vitamin B12-rich foods where appropriate.
Some people only need short-term treatment, while others may require lifelong vitamin B12 replacement and regular monitoring.
Looking to support your vitamin B12 intake? If your healthcare professional recommends supplementation, SunVit D3's Vitamin B12 supplements provide a convenient way to help maintain healthy vitamin B12 levels alongside a balanced diet and healthy lifestyle.
Important: Food supplements should not be used as a substitute for a varied, balanced diet and healthy lifestyle.
Foods Rich in Vitamin B12
One of the best ways to maintain healthy vitamin B12 levels is through a balanced diet.
Good dietary sources include:
- Beef and lamb
- Clams
- Salmon, tuna, and sardines
- Chicken
- Eggs
- Milk, cheese and yoghurt
- Fortified breakfast cereals
- Fortified plant-based milks
- Nutritional yeast fortified with vitamin B12
If you follow a vegan or vegetarian diet, choosing fortified foods or taking a vitamin B12 supplement may help you meet your daily requirements.
How Much Vitamin B12 Do You Need?
The NHS recommends that adults aged 19 to 64 need around 1.5 micrograms (mcg) of vitamin B12 each day. Most people who eat meat, fish, eggs, or dairy products can meet this requirement through a balanced diet.
However, because vitamin B12 isn't naturally found in plant foods, people following a vegan diet—and some vegetarians—may need to rely on fortified foods or supplements to maintain healthy vitamin B12 levels.
Complications of Vitamin B12 Deficiency
While many people recover well with prompt treatment, untreated vitamin B12 deficiency can lead to more serious health problems over time.
Possible complications include:
- Permanent nerve damage (peripheral neuropathy), which may cause ongoing numbness, tingling, or muscle weakness.
- Problems with balance and coordination, making walking more difficult.
- Memory and cognitive problems, particularly if the deficiency is severe or prolonged.
- Vision problems caused by damage to the optic nerve (rare).
- Temporary infertility, which usually improves once the deficiency is treated.
If you're pregnant or planning a pregnancy, maintaining healthy vitamin B12 levels is also important, as severe deficiency may increase the risk of certain birth defects, particularly when combined with folate deficiency.
Fortunately, most complications can be prevented by recognising symptoms early and receiving appropriate treatment.
Can You Prevent Vitamin B12 Deficiency?
Not every case of vitamin B12 deficiency can be prevented, especially when it's caused by conditions that affect absorption. However, many people can reduce their risk by:
- Eating a balanced diet that includes vitamin B12-rich foods.
- Choosing fortified foods if following a plant-based diet.
- Taking supplements if recommended by a healthcare professional.
- Attending regular health checks if you're at higher risk due to age, certain medical conditions, or long-term medication use.
If you've previously been diagnosed with vitamin B12 deficiency, continue following your GP's treatment plan, even if your symptoms improve.
Final Thoughts
Vitamin B12 is essential for healthy red blood cells, nerve function, and normal energy metabolism. Because deficiency symptoms often develop gradually, they're easy to mistake for everyday tiredness or stress.
If you're experiencing ongoing fatigue, pins and needles, memory problems, or other symptoms of vitamin B12 deficiency, don't ignore them. An early diagnosis can help prevent complications and ensure you receive the right treatment.
If your healthcare professional recommends supplementation, choosing a high-quality vitamin B12 supplement can be a simple way to help maintain healthy vitamin B12 levels as part of a balanced diet and healthy lifestyle.
Disclaimer: This article is for general informational purposes only and should not replace professional medical advice. If you think you may have a vitamin B12 deficiency or are experiencing persistent symptoms, speak to your GP or another qualified healthcare professional for assessment and appropriate treatment.
