10 Warning Signs of Vitamin B12 Deficiency
Vitamin B12 is a nutrient your body needs but cannot make on its own. You have to get it from food or supplements. It plays a key role in making red blood cells, keeping your nerves healthy, and supporting your brain and energy.
Vitamin B12 deficiency is common, and it can develop slowly over time. The signs are often mild at first and easy to mistake for everyday tiredness or stress. But left untreated, low B12 can affect your blood, your nerves, and your overall health.
The good news is that vitamin B12 deficiency is usually simple to diagnose and treat. A blood test can check your levels, and treatment is often straightforward. This guide explains the common signs of B12 deficiency, what causes it, who is at risk, how to treat it, and when to see a doctor.
Quick Overview
| Question | Short answer |
|---|---|
| What is it? | Low levels of vitamin B12 in the body |
| Why it matters | B12 supports blood, nerves, brain, and energy |
| Common signs | Tiredness, weakness, tingling, pale skin |
| Main causes | Poor diet, absorption problems, some conditions |
| At higher risk | Vegans, older adults, some medical conditions |
| How to check | A simple blood test |
| When to see a doctor | Ongoing symptoms, or if you are at higher risk |
Why Vitamin B12 Matters
Vitamin B12 does several important jobs in the body. It helps make healthy red blood cells, which carry oxygen around your body. It keeps your nervous system working properly. And it supports your brain, mood, and energy levels.
Because B12 is involved in so many functions, a deficiency can cause a wide range of symptoms. These can affect your blood, your nerves, and your mind.
Your body cannot make vitamin B12. You get it mainly from animal foods such as meat, fish, eggs, and dairy. Your body then absorbs it through a specific process in your gut. A problem at any stage, whether from diet or absorption, can lead to a deficiency. Because tiredness is such a common early sign, our guide on fatigue causes covers the many reasons for low energy.
10 Common Signs of Vitamin B12 Deficiency
Low B12 often causes mild symptoms at first. They can build up slowly, which makes them easy to miss. Here are the common signs to look out for.
1. Tiredness and fatigue. Feeling tired and low on energy is one of the most common signs. Low B12 affects red blood cells, which carry oxygen, so you can feel drained.
2. Weakness. A general feeling of weakness often comes with the tiredness of B12 deficiency.
3. Pale or yellowish skin. Low B12 can affect red blood cell production, which can make the skin look pale or slightly yellow.
4. Tingling or numbness. B12 is vital for nerve health. Low levels can cause a “pins and needles” feeling, or numbness, often in the hands and feet.
5. Breathlessness. Because B12 affects the blood’s ability to carry oxygen, some people feel short of breath, especially with activity.
6. Dizziness. Feeling dizzy or lightheaded can occur, linked to the effects on the blood. Our guide on dizziness causes covers this symptom in more detail.
7. A sore or red tongue. Some people with low B12 develop a sore, red, or smooth tongue, and sometimes mouth ulcers.
8. Problems with memory or thinking. B12 supports the brain. Low levels can cause problems with memory, concentration, or a feeling of “brain fog.”
9. Mood changes. Low B12 can affect mood, and some people notice low mood or irritability.
10. Balance or walking problems. In more significant deficiency, the effects on the nerves can cause problems with balance or walking. This is a sign that needs prompt medical attention.
These signs can have many causes. So they are prompts to check your B12, not proof of deficiency. Some nerve-related symptoms can become long-lasting if a deficiency is not treated, which is why it is important not to ignore them.
What Causes Vitamin B12 Deficiency?
Vitamin B12 deficiency happens when your body does not get enough B12, or cannot absorb it properly. There are two main groups of causes.
Diet. Vitamin B12 is found mainly in animal foods. People who eat little or no animal produce, such as vegans and some vegetarians, can become low in B12 unless they get it from fortified foods or supplements.
Absorption problems. Even with enough B12 in the diet, some people cannot absorb it properly. This can be due to certain conditions affecting the gut, or a condition where the body cannot absorb B12 from food. Some stomach and bowel conditions, and some surgeries, can also affect absorption.
Age. As people get older, the body can become less able to absorb B12 from food. Older adults are therefore at higher risk.
Some medications. Certain long-term medications can affect B12 levels over time.
Understanding the cause matters, because it affects the treatment. For example, a dietary deficiency may be treated differently from an absorption problem. A doctor can work out which applies to you.
Who Is Most at Risk?
Some groups are more likely to have low vitamin B12. You may be at higher risk if you:
- Follow a vegan or strict vegetarian diet
- Are an older adult
- Have a condition that affects B12 absorption
- Have had certain stomach or bowel surgery
- Take certain long-term medications
- Have a family history of B12 absorption problems
If you fall into one of these groups, it is worth being aware of the signs and speaking to a doctor if you have symptoms. People who avoid animal foods are often advised to take a B12 supplement or eat fortified foods, since diet alone may not provide enough.
How Vitamin B12 Deficiency Is Diagnosed
The way to check for B12 deficiency is a blood test. This measures the level of vitamin B12 in your blood, and can also check your red blood cells for signs of anaemia.
A doctor may suggest a test if you have symptoms of deficiency, or if you have risk factors. If the test shows low B12, the doctor may do further tests to find the cause. This helps decide the best treatment.
If you think you may be low, it is worth speaking to a doctor rather than guessing. This is especially important because some symptoms, particularly nerve-related ones, are best treated early. Guessing and self-treating can delay finding the real cause.
How Vitamin B12 Deficiency Is Treated
Treatment for B12 deficiency depends on the cause. It is usually effective once started.
For dietary deficiency. If the cause is diet, treatment may involve B12 supplements, or eating more B12-rich or fortified foods. For vegans and vegetarians, a regular supplement or fortified foods can maintain healthy levels.
For absorption problems. If the body cannot absorb B12 from food, supplements taken by mouth may not be enough. In these cases, B12 is sometimes given by injection, or in another form, as advised by a doctor.
The right treatment depends on why you are low, which is why a doctor’s assessment matters. Many people need ongoing treatment if the underlying cause continues. With the right treatment, symptoms often improve, though some nerve-related symptoms are best treated early to prevent them becoming long-lasting.
Do not try to self-treat significant B12 deficiency with high-dose supplements alone, especially if you have nerve symptoms. See a doctor, so the cause is found and the right treatment is used.
Foods Rich in Vitamin B12
Vitamin B12 is found mainly in animal foods. Good sources include:
- Meat
- Fish
- Eggs
- Dairy products such as milk and cheese
- Fortified foods, such as some breakfast cereals and plant milks
For most people who eat animal produce, a normal balanced diet provides enough B12. For vegans and strict vegetarians, fortified foods and supplements are the main way to get enough, since plant foods do not naturally contain much B12. If you avoid animal foods, it is worth making sure you have a reliable source of B12.
B12 Deficiency and Anaemia
One of the main effects of low vitamin B12 is a type of anaemia. Understanding this helps explain many of the symptoms.
Anaemia means having too few healthy red blood cells, or cells that do not work well. Red blood cells carry oxygen around your body. Vitamin B12 is needed to make healthy red blood cells. So when B12 is low, the body cannot make them properly, and a type of anaemia can develop.
This is why many signs of B12 deficiency, such as tiredness, weakness, breathlessness, and pale skin, are the same as the signs of anaemia. They all come from the body’s reduced ability to carry oxygen.
Low iron causes a different type of anaemia, but with some overlapping symptoms. This is why tiredness and weakness can come from either low B12 or low iron. Our guide on iron deficiency explains that condition. Because the symptoms overlap, a blood test is the reliable way to find out which is behind your symptoms, and a doctor can test for both at once.
Why Nerve Symptoms Matter Most
While many symptoms of B12 deficiency improve easily with treatment, the nerve-related ones deserve special attention. This is the most important thing to understand about low B12.
Vitamin B12 is essential for healthy nerves. When B12 is low for a long time, it can affect the nerves, causing tingling, numbness, and, in more significant cases, problems with balance and walking. These nerve symptoms are different from the blood-related ones.
The key point is that nerve symptoms are best treated early. If a B12 deficiency affecting the nerves is caught and treated in good time, symptoms often improve. But if it is left untreated for a long time, some nerve damage can become long-lasting. This is why numbness, tingling, and balance problems should not be ignored, and why they are a reason to see a doctor promptly rather than waiting.
This is also why guessing and self-treating is not a good idea for significant B12 deficiency. Getting a proper diagnosis and the right treatment, at the right time, gives the best chance of a full recovery. If you have nerve symptoms alongside other signs of low B12, see a doctor without delay.
When to See a Doctor
Speak to a doctor if:
- You have ongoing tiredness, weakness, or breathlessness
- You have tingling, numbness, or balance problems
- You have several risk factors for low B12
- You follow a vegan or strict vegetarian diet and have symptoms
- Your symptoms are affecting your daily life
- You are unsure whether you need a supplement or test
See a doctor promptly if you have nerve-related symptoms such as numbness, tingling, or problems with balance or walking. These are best treated early, as some can become long-lasting if a deficiency is left untreated.
A doctor can arrange a blood test and find the cause. Most B12 deficiency is treatable once identified, so it is worth getting checked rather than ignoring ongoing symptoms. The NHS guidance on vitamin B12 deficiency explains the tests and treatment.
Final Thoughts
Vitamin B12 deficiency is common, and its signs can be easy to miss at first. Tiredness, weakness, pale skin, tingling, and problems with memory or balance can all point to low levels. Because the symptoms build up slowly, many people live with a deficiency without realising it.
The reassuring news is that B12 deficiency is usually simple to diagnose and treat. A blood test can confirm it, and treatment, whether through diet, supplements, or injections, is often very effective. What matters is not ignoring the symptoms, especially nerve-related ones, which are best treated early.
If you have symptoms or risk factors, particularly if you follow a vegan diet or are an older adult, it is worth speaking to a doctor. Looking after your B12 is a simple step that supports your blood, nerves, brain, and energy. For most people, the right diet, fortified foods, or a supplement when needed are all it takes to keep their levels healthy.
Medical disclaimer: This article is for general educational information only. It is not a substitute for professional medical advice, diagnosis, or treatment. See a doctor for ongoing symptoms, and seek prompt advice for numbness, tingling, or balance problems.
Frequently Asked Questions
What are the signs of vitamin B12 deficiency? Common signs include tiredness, weakness, pale or yellowish skin, tingling or numbness in the hands and feet, breathlessness, dizziness, a sore red tongue, memory or concentration problems, mood changes, and, in more significant cases, balance or walking problems.
What causes low vitamin B12? The main causes are a diet low in animal foods, and problems absorbing B12 from food. Vegans and strict vegetarians are at risk from diet, while some gut conditions, certain surgeries, older age, and some medications can affect absorption. A doctor can find the cause.
How can I increase my vitamin B12? If the cause is diet, eating more B12-rich foods such as meat, fish, eggs, and dairy, or fortified foods and supplements, can help. If the cause is an absorption problem, supplements by mouth may not be enough, and a doctor may recommend injections or another form.
Who is at risk of B12 deficiency? People at higher risk include vegans and strict vegetarians, older adults, people with conditions affecting B12 absorption, those who have had certain stomach or bowel surgery, and people taking certain long-term medications. These groups should be aware of the signs.
Can low B12 cause tiredness? Yes. Tiredness and weakness are among the most common signs of B12 deficiency, because low B12 affects red blood cells that carry oxygen. However, fatigue has many causes, so a blood test is needed to confirm whether low B12 is a factor.
Can vegans get enough vitamin B12? Vitamin B12 is found mainly in animal foods, so vegans need to get it from fortified foods or supplements. With a reliable source, vegans can maintain healthy B12 levels. Anyone following a vegan or strict vegetarian diet should ensure they have a regular source of B12.
Is vitamin B12 deficiency serious? Most B12 deficiency is treatable once identified. However, if left untreated, some symptoms, particularly nerve-related ones like numbness, tingling, and balance problems, can become long-lasting. This is why it is important not to ignore the signs and to seek treatment early.
How is vitamin B12 deficiency diagnosed? It is diagnosed with a blood test that measures your B12 level and checks your red blood cells. If the test shows low B12, a doctor may do further tests to find the cause, which helps decide the best treatment. Guessing is not reliable, so testing is important.