Vitamin B12 deficiency: Symptoms, consequences and treatment

Our bodies have vitamin stores, which means that vitamin B₁₂ deficiency usually develops quite slowly. The first signs of vitamin B₁₂ deficiency are often non-specific and subtle, and are the same for both men and women. They include:

• Fatigue

• Feeling weak

• Lack of motivation

• Difficulty concentrating

• Dizziness and headaches

Since vitamin B12 is important for blood formation, a deficiency can also lead to anaemia. Typical signs of anaemia include pale skin, shortness of breath and a rapid heartbeat.

In the long term, untreated vitamin B₁₂ deficiency can damage the nerves and cause the following symptoms:

• Numbness

• Tingling

• Muscle weakness

• Depressive moods

• Confusion

• Impaired brain function

A vitamin B12 deficiency can have a negative effect on concentration and general well-being, among other things. Studies show that a good supply of vitamin B₁₂ in combination with folic acid and vitamin B₆ can help to lower homocysteine levels. This is positive because elevated homocysteine levels are associated with an increased risk of age-related macular degeneration (AMD), a condition that can lead to vision loss in old age. Studies also show that vitamin B12 deficiency may be linked to dry eyes.

Vegans are particularly at risk of developing vitamin B12 deficiency due to their purely plant-based diet, as vitamin B12 is found almost exclusively in animal products.

There are an estimated 75 million voluntary vegetarians worldwide and 1.45 billion people who are vegetarian due to a lack of options. A strictly vegetarian/vegan diet provides at most 0.5 µg of vitamin B12 per day, which is why this type of diet is one of the main risk factors for B12 deficiency.

Children of vegan or strictly vegetarian mothers may also be affected by B12 deficiency.

Surgery on the gastrointestinal tract can lead to deficiency symptoms. Chronic inflammation of the stomach lining can also cause a B12 deficiency, as can excessive production of stomach acid. 

With age, the performance of the gastrointestinal tract declines, meaning that vitamins are no longer absorbed as effectively.

Taking certain medications, such as those for diabetes, can affect B12 levels.

Those who frequently consume wine, beer and other alcoholic beverages should also keep an eye on their vitamin B12 levels.

Since the symptoms of vitamin B₁₂ deficiency are often ambiguous, a blood test is essential for diagnosis. The standard serum vitamin B₁₂ level is often insufficient, as it is a relatively non-specific marker.

Instead, experts recommend testing additional biomarkers such as holotranscobalamin II (holo-TC) and methylmalonic acid (MMA), which together provide a more reliable picture. Low holo-TC levels below 35 pmol/l are the earliest marker of an impending deficiency, while elevated MMA levels above 271 nmol/l indicate that vitamin B₁₂ stores are already depleted.

When checking and optimising vitamin B12 levels, it may be useful to also measure folic acid and vitamin B6 levels, as these three vitamins are linked in the metabolism. A deficiency in vitamin B6 or folic acid can lead to symptoms similar to those of a vitamin B12 deficiency.

The best way to prevent vitamin B12 deficiency is to eat a balanced diet – but this is especially important for people who eat animal products. This is because B12 is found in large quantities in meat, fish, poultry, eggs and dairy products, while plant-based foods contain only small amounts. However, there are also fortified products such as breakfast cereals and spreads that can contribute to your vitamin B12 intake.

If you follow a vegan diet or eat very little animal products, you should consider taking vitamin B₁₂ in the form of dietary supplements or specifically choosing fortified products. According to the German Nutrition Society (DGE), the recommended daily intake is 4 micrograms. If you eat animal products, your body absorbs the vitamin several times a day in small amounts via an active absorption pathway.

However, if you rely on supplements, for example due to a plant-based diet, you should choose higher doses. This allows the body to use the passive absorption pathway for absorption. This is less efficient and only comes into play when significantly higher amounts of B₁₂ are consumed.

Vitamin B12 injections are primarily used when there is already a severe vitamin B12 deficiency, which is usually accompanied by symptoms such as severe fatigue, anaemia or nerve damage. Such a deficiency usually develops over several years due to digestive problems, the use of certain medications or a vegan diet without additional supplementation. The injection serves to correct vitamin B12 levels as quickly as possible. In the vast majority of cases, vitamin B12 levels can then be optimised by taking high-dose supplements orally.

A vitamin B12 deficiency can be quickly corrected with an injection or oral administration, as both methods allow large amounts of vitamin B12 to be absorbed. In both cases, initial improvements are noticeable after just a few days, at least in terms of fatigue. However, depending on the type of symptoms, it can take up to several weeks for the affected cells to regenerate properly.