Vitamin B12 deficiency: symptoms, causes and treatment

Vitamin B12 is a vital water-soluble vitamin that is essential for DNA synthesis, normal red blood cell formation, and protection of nerve fibers. Its deficiency develops gradually and may remain unnoticed for a long time. According to studies, it affects up to 15–20% of adults over 50, and is more common for people following a vegan diet, those with atrophic gastritis, or impaired absorption in the gastrointestinal tract.

Without timely correction, it can lead to anemia and damage to the nervous system.

Functions of vitamin B12 in the body

Vitamin B12 plays a key role in metabolic processes. It acts as a cofactor for enzymes involved in cellular energy production and supports overall metabolism.

One of its main functions is participation in the formation of red blood cells that carry oxygen throughout the body. With sufficient B12 levels, these cells have a normal structure and function effectively.

Vitamin B12 is also critically important for the nervous system. It supports the formation of the myelin sheath, which protects nerve fibers and ensures fast and accurate signal transmission.

In addition, it is involved in the conversion of homocysteine into methionine — a process necessary for DNA synthesis and neurotransmitter production (serotonin, dopamine). This directly affects cognitive function, mood, and concentration.

Another important function is the conversion of nutrients into energy. When B12 is deficient, people often experience chronic fatigue and reduced endurance.

Symptoms of deficiency

Vitamin B12 deficiency usually develops gradually over 3–12 months, and early symptoms are often nonspecific.

From the hematological perspective, megaloblastic anemia develops, where red blood cells become enlarged and ineffective. This leads to fatigue, tachycardia, shortness of breath, and weakness.

Neurological symptoms include paresthesia (tingling and numbness) in the hands and feet, impaired coordination, and decreased sensitivity, associated with nerve damage.

Changes in the skin and mucous membranes may appear, including pale-yellow skin tone and glossitis (smooth red tongue), and sometimes hyperpigmentation.

Psychological symptoms include brain fog, decreased concentration, and depressive states, due to impaired neurotransmitter balance.

Gastrointestinal symptoms may include loss of appetite, nausea, constipation, as well as general weakness and low blood pressure.

Diagnosis

Vitamin B12 deficiency is suspected when levels are below 200 pg/mL, often accompanied by elevated homocysteine levels.

It is important not only to confirm the deficiency but also to determine its cause, as this affects treatment.

Conclusion

Vitamin B12 deficiency is a common but reversible condition, especially when detected early.

The earlier it is identified, the easier it is to treat without complications.

Correction should always be done under medical supervision to ensure the right approach.

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Vitamin B12 deficiency: why fatigue, brain fog and tingling appear

Functions of vitamin B12 in the body

Symptoms of deficiency

Diagnosis

Conclusion