© Anna Shvets
May 20, 2026
Marianne Waldenfels
Fatigue, brain fog, tingling in the hands and feet? A vitamin B12 deficiency can go unnoticed for years. Here’s what to watch for
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For most people in Germany, vitamin B12 plays hardly any role in everyday life. For others, such as vegansthe elderly, or people with certain diseases, an undiscovered deficiency can have serious consequences. On social media and podcasts, it is touted as an energy booster and health hack, often together with ashwagandha, magnesium or collagen powder. A sober look at a nutrient that is neither a miracle cure nor should be underestimated.
Vitamin B12, also known chemically as cobalamin, is involved in several key metabolic processes: it regulates the formation of red blood cells, keeps the nervous system functioning properly, and is needed for DNA synthesis. The daily requirement for an adult is about 2.4 micrograms – an extremely small amount that the body cannot produce on its own and must be completely absorbed through food.
What makes this nutrient special is that the body can store B12 in the liver for years. A deficiency therefore develops slowly, often over months or even years, without those affected initially noticing.
A deficiency often initially manifests itself through general complaints. These include:
If left untreated, neurological symptoms may occur. Typical symptoms include tingling or numbness in the hands and feet, unsteady gait, or muscle weakness. Some affected individuals also report depressive moods or irritability.
In severe cases, memory disturbances or confusion may even occur. Especially neurological damage can take a long time to recover – sometimes they remain permanent.
However, it is important to note: These complaints are not specific. Other conditions can also cause similar symptoms. Therefore, medical clarification is advisable.
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Certain groups of people are particularly at risk of developing a B12 deficiency:
Vegans and strict vegetarians are at the forefront. Since B12 is practically exclusively found in animal products such as meat, fish, eggs, or dairy products, a purely plant-based diet without targeted supplementation is not sensible in the long term. Enriched plant drinks hardly meet the needs in practice.
People over 50 are another important risk group. As you age, the stomach produces less stomach acid and less of the so-called intrinsic factor – a protein necessary for the absorption of B12 in the intestine. According to studies, between 10 and 30 percent of people over 50 are affected.
People with gastrointestinal diseases such as Crohn's disease, ulcerative colitis, or celiac disease also have restricted B12 absorption. The same applies after bariatric surgeries or when parts of the stomach are removed.
Long-term medication is an often underestimated risk factor: Those who regularly take proton pump inhibitors like omeprazole or the diabetes medication metformin should have their B12 status checked regularly.
The standard value in the blood test – total B12 – alone is not sufficient for a reliable diagnosis. It is more useful to determine holotranscobalamin (Holo-TC), which only represents the biologically usable portion. Additionally, methylmalonic acid (MMA) can be measured, which increases in a functional deficiency. Homocysteine provides additional clues but is less specific.
As a guideline: Levels below 200 pg/ml are considered deficient, the range between 200 and 400 pg/ml is a diagnostic gray area that requires further investigation.
Vitamin B12 can be taken in different forms: as tablets or capsules, as drops or lozenges, and in cases of severe deficiency, also as an injection.
Cyanocobalamin and methylcobalamin are particularly widespread. Both forms are generally considered effective. Cyanocobalamin is often used because it is well-researched and relatively inexpensive.
The recommended daily dose depends on your situation:
For prevention in vegans: 250-500 µg daily or 2500 µg once weekly
In case of mild deficiency: 1000 µg daily for several weeks to months
In case of severe deficiency with neurological symptoms: High-dose injections according to medical protocol, often 1000 µg daily for a week, then weekly
Overdose: B12 is very safe as excess amounts are excreted through the kidneys. Even high-dose supplements with several thousand micrograms are considered harmless. Some studies suggest possible links between very high doses and acne or certain types of cancer, but the evidence is not clear.
Those who consume animal products can easily meet their B12 needs. The richest sources per 100g:
Plant-based foods like algae (nori, spirulina) or fermented products like sauerkraut contain only inactive B12 analogs, which cannot be used by the human body and can even block the absorption of real B12.
The most common signs are persistent fatigue, concentration problems, and paleness. Later, tingling in the extremities or mood changes may occur. Since these symptoms are non-specific, a deficiency can only be reliably diagnosed by a blood test.
This depends on the severity of the deficiency and the chosen therapy form. Mild deficiencies often improve with oral supplementation within weeks to months. Neurological symptoms can take significantly longer – and in severe cases, residual complaints may persist.
The dosage and form are more important than the brand. For most purposes, 500–1000 µg daily is sufficient. If absorption is impaired, intake should be coordinated with a doctor.
Adequate intake through conventional plant-based foods is not possible. Vegans rely on supplements or fortified products – and should regularly have their status checked by a doctor.
Yes. The need slightly increases during pregnancy and breastfeeding. A deficiency in the mother can impair the child's neurological development. Vegan pregnant women should definitely supplement and seek medical supervision.
Vitamin B12 is not a lifestyle supplement, it is an essential nutrient with clearly defined risk groups. Those who eat a balanced diet with animal products and have no absorption problems need not worry. However, those who live vegan, are older, or take certain medications long-term should know their status.
The recommendation is simple: If there is suspicion or as a member of a risk group, have your holotranscobalamin and MMA levels determined by your doctor.
