© Anna Shvets
May 4, 2026
Marianne Waldenfels
Fatigue, poor concentration, low motivation? A vitamin B12 deficiency could be to blame—affecting millions and often going unnoticed. Yet this essential nutrient is vital for energy, brain function, and overall well-being
Vitamin B12 (cobalamin) is essential for keeping your body running smoothly. It supports red blood cell formation, maintains a healthy nervous system, and plays a key role in DNA production. When levels are low, the body struggles to keep up—often resulting in fatigue and reduced performance. Adults need around 2.4 µg per day, with increased requirements during pregnancy and breastfeeding.
A B12 deficiency usually develops gradually because the liver can store the vitamin – reserves last for two to four years in healthy people. The symptoms are varied and non-specific, making diagnosis difficult:
Common early symptoms:
Neurological symptoms in advanced deficiency:
In severe cases:
Confusion and memory loss
Important: These symptoms can also have other causes. If a deficiency is suspected, you should have your B12 status checked by a doctor.
Certain groups of people are particularly at risk of developing a B12 deficiency:
Along with the total B12 value, other blood parameters provide valuable information:
Values below 200 pg/ml are considered a deficiency, 200–400 pg/ml as a gray area.
In case of proven deficiency or for prevention in risk groups, different forms of administration are available:
Tablets and capsules: The most common form for daily intake. Dosages of 250-1000 µg are common, as only a small part is passively absorbed through the intestinal mucosa.
Sublingual tablets and drops: Placed or dripped under the tongue and partially absorbed directly through the oral mucosa.
Injections: In cases of severe deficiency or when oral absorption is impaired, B12 injections are administered intramuscularly. The initial dose is often 1000 µg daily or several times a week.
Methylcobalamin vs. Cyanocobalamin: Cyanocobalamin is the synthetic, cost-effective standard form with good study data. Methylcobalamin is a bioactive form that the body can directly utilize. Both are effective, but Cyanocobalamin is often preferred due to better data.
The recommended daily dose depends on your situation:
For prevention in vegans: 250-500 µg daily or 2500 µg once weekly
For mild deficiency: 1000 µg daily for several weeks to months
For 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 by 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 cancers, but the evidence is not conclusive.
Those who consume animal products can meet their B12 needs well. The most abundant sources per 100g:
Plant-based foods such as algae (Nori, Spirulina) or fermented products such as sauerkraut contain only inactive B12 analogs, which cannot be utilized by the human body and can even block the absorption of real B12.
With daily supplementation, blood levels usually normalize after 6-12 weeks. However, neurological symptoms can take months to years to subside—or remain permanent in advanced stages.
Yes, with regular consumption of sufficient amounts. However, studies show that many vegetarians still have suboptimal levels, as the amounts are often insufficient.
Yes, a folic acid deficiency can mask B12 deficiency symptoms. Vitamin C improves absorption, while high doses of zinc can impair it.
The timing doesn't matter much. Some people report better tolerance when taken with meals.
Vitamin B12 is an essential nutrient that deserves special attention in certain groups of people. The hype around B12 as an energy booster for healthy, well-supplied people is not scientifically sustainable – those with normal levels will not become more efficient with additional B12.
For vegans, however, supplementation is absolutely necessary, and older people, people with gastrointestinal diseases, or certain medications should regularly check their status.
Our recommendation: If you suspect a deficiency or are a member of a risk group, have your B12 status including holotranscobalamin checked by your family doctor. Targeted supplementation when there is a proven need is sensible and safe – indiscriminate intake of high-dose preparations without indication, on the other hand, is unnecessary.
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