B12 Deficiency & Neurology: Brain Fog, Tingling & Balance

Neurology 09 October, 2026

Understanding vitamin B12 and its role in neurology

What is vitamin B12?

Vitamin B12 (also called cobalamin) is found naturally in animal products, such as meat, fish and dairy. Importantly, your body can’t make vitamin B12, which means most people get vitamin B12 from their diet.

You need vitamin B12 to make red blood cells, to keep your nerves healthy and to maintain the integrity of your DNA. Cobalamin deficiency can affect different aspects of your health and, in particular, can cause neurological symptoms.

A cobalamin deficiency may also lead to high levels of homocysteine, which can increase the risk of various diseases. Maintaining a normal level of both vitamin B12 and folate is essential for long-term health.

How vitamin B12 supports the nervous system

The nerves in your body are wrapped in a layer of insulation called a myelin sheath. This protects the nerves and helps electrical signals move faster along the nerves.

Vitamin B12 is required to make myelin. Therefore, vitamin B12 is essential for the development and process of insulating nerves with myelin, which is called myelination. This is needed to protect the spinal cord and ensure the brain works correctly.

Vitamin B12 deficiency can result in demyelination because there isn’t enough myelin being produced to maintain the myelin sheath. B12 deficiency also negatively affects the repair of damaged nerves because there isn’t enough myelin available for rebuilding the myelin sheath. Left untreated, this can lead to subacute combined degeneration, a condition where the spinal cord is damaged due to a lack of nutrients.

As demyelination of nerves due to vitamin B12 deficiency can affect both the nerves in the brain and those outside of the brain, it can cause a range of neurological symptoms.

In some cases, the recreational use of nitrous oxide — commonly called laughing gas — can cause a rapid deficiency. This is because nitrous oxide interferes with how the body uses vitamin B12.

Vitamin B12 deficiency: causes and risk factors

Pernicious anaemia and malabsorption

The leading cause of B12 deficiency is pernicious anaemia. This is an autoimmune condition where your immune system mistakenly attacks your own healthy tissue.

For most people with pernicious anaemia, the body creates antibodies that attack and destroy cells in the stomach called parietal cells. These cells make hydrochloric acid and a substance called intrinsic factor, which is essential for the body to be able to absorb vitamin B12.

Vitamin B12 binds to intrinsic factor in the stomach. This then travels to the last section of your small intestine (ileum), where it’s finally absorbed into your bloodstream. Once in your blood, vitamin B12 can be transported to cells throughout your body where it’s required.

Without enough hydrochloric acid or the intrinsic factor protein, the right amount of vitamin B12 can’t pass from your small intestine into your blood.

In some cases of pernicious anaemia, it’s not only the parietal cells making intrinsic factor that are destroyed. Antibodies are also made that attach to intrinsic factor by itself or to intrinsic factor bound to vitamin B12. In both cases, this stops vitamin B12 from being absorbed into your blood.

Your risk of developing pernicious anaemia increases with age. The mean age for diagnosis is often over 60 and it’s more common in women.

Diet

Another major risk factor for developing vitamin B12 deficiency is your diet. As vitamin B12 is mainly found in animal products, your risk is higher if you don’t eat meat, fish or dairy, or don’t eat enough of these foods.

This makes it more likely to occur if you follow a vegetarian or vegan diet. However, you can compensate for the lack of naturally-occurring vitamin B12 by eating food fortified with vitamin B12 (eg fortified breakfast cereals, plant-based milks and nutritional yeast) or taking a vitamin B12 supplement.

It is important to ensure you also get enough folate — folate and vitamin B12 work together on several bodily functions, and vitamin B12 activates folate. However, high levels of folic acid can sometimes hide the signs of a vitamin B12 deficiency.

It’s important to note that your body stores enough vitamin B12 to last 2–5 years, so switching to a vegan or vegetarian diet may not immediately result in vitamin B12 deficiency.

Gut diseases and medications

Conditions that make it difficult for your gut to absorb nutrients can also lead to vitamin B12 deficiency.

For example, an inflammatory bowel disease called Crohn’s disease causes nutritional deficiencies due to inflammation along different parts of the digestive system. If it causes inflammation of the ileum, where vitamin B12 is absorbed, it can lead to B12 deficiency.

Patients with diabetes should also be aware that certain medications can affect vitamin B12 levels over time.

In contrast, if you have another type of inflammatory bowel disease called ulcerative colitis, vitamin B12 deficiency is less likely to happen. This is because ulcerative colitis affects the colon, not the ileum.

Gastric surgery to remove all or part of your stomach can also increase your risk of vitamin B12 deficiency. Stomach cells called parietal cells are needed to make intrinsic factor, which is essential for vitamin B12 absorption.

Repeated recreational use of nitrous oxide can cause a rapid progression of subacute combined degeneration in those with low vitamin B12 levels.

Recognising symptoms: brain fog, tingling and balance issues

As mentioned earlier, vitamin B12 deficiency can affect the health of nerves in your brain and nerves outside your brain (peripheral nerves), causing different neurological symptoms.

Warning signs of peripheral neuropathy

Peripheral neuropathy refers to damage to your peripheral nerves, for example, due to vitamin B12 deficiency.

The most common symptom is numbness and/or tingling in your arms, legs, hands and feet. This can lead to difficulty walking and change the way you walk (your gait). If you are experiencing symptoms like these, it is vital to determine the cause.

You can also develop muscle weakness and a reduced ability to feel sensations like vibrations in your limbs. This leads to poor balance. Severe cases of peripheral neuropathy or subacute combined degeneration can make life difficult if not treated promptly.

Brain and central nervous system symptoms

The effect of vitamin B12 deficiency on the brain can:

Make it harder to remember and understand things
Impair your judgement
Cause anxiety, confusion, low mood and depression

Vitamin B12 deficiency can also damage your optic nerve. This can cause vision problems, such as blurred vision, reduced colour vision and blind spots. A folate deficiency may cause similar problems, and many people have both a B12 and folate deficiency.

Symptoms that are not neurological

Vitamin B12 deficiency causes your body to make abnormal red blood cells, leading to anaemia. This makes it harder for oxygen to be effectively transported to your tissues. This can cause tiredness, low energy, a sore tongue and muscle weakness.

While most people notice the fatigue first, the neurological symptoms are often the most concerning part of the condition.

Diagnosing B12 deficiency

If you’re experiencing symptoms of B12 deficiency, it is important to have these symptoms investigated.

A doctor can usually determine if you have a vitamin B12 deficiency from your symptoms and a blood test. Early detection is essential to stop the progression of neurological damage.

The blood test checks patients for vitamin B12 levels – the normal range is 180–914 ng/L. A blood test will usually also check the size of red blood cells as vitamin B12 deficiency causes abnormally large red blood cells. Doctors will also check for folate levels to rule out a folate deficiency, as taking folic acid can mask a lack of vitamin B12.

Treatment options

Vitamin B12 deficiency is initially treated with vitamin B12 injections every other day until your symptoms improve. After this period, your treatment will depend on the cause of your B12 deficiency.

If it is caused by pernicious anaemia, you’ll continue to have vitamin B12 injections every 2–3 months for life. This treatment is needed to prevent subacute combined degeneration from returning.

If it’s due to your diet, your doctor will recommend taking daily vitamin B12 tablets. They may also suggest a folic acid supplement if you also have a folate deficiency. If your diet is not enough to prevent a lack of vitamin B12, you may still need vitamin B12 injections.. Your doctor will regularly review your blood test results to ensure your vitamin B12 levels remain normal.

Check your vitamin B12 levels

Do you have tingling hands or feet? Feeling more tired than usual? You may have a vitamin B12 deficiency. Get the clarity you need with a simple blood test with Vista Health.

Simply book our 360 Health MOT package to check your vitamin B12 levels, as well as a range of other health markers like folate, at one of our clinics nationwide.