Vitamin B 12 deficiency - symptoms and causes

Vitamin B 12 deficiency - symptoms and causes

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Everyone is talking about vitamin B12 deficiency, various companies advertise dietary supplements with the vitamin, but what does a deficiency mean for our health at all? Why does the organism need this chemical substance? Which population groups risk undersupply?

An overview

  • Vitamin B12 plays an important role in cell division, blood formation and the functioning of the nervous system.
  • Contrary to what advertising for vitamin B12 supplements suggests, a deficiency is rather rare, since most people in Germany are adequately supplied with the substance.
  • Healthy people don't usually need vitamin supplements.
  • Since vitamin B12 is increasingly contained in animal products, vegans are an exception because they have to take additional vitamin B12 to stay healthy.

Why do we need the vitamin?

Vitamin B12 denotes chemical compounds with cobalamins and is mostly bound to proteins. We only need these chemical compounds in a negligible amount, but they are involved in various processes of the organism. This includes:

  • DNA synthesis,
  • the formation of blood and cells,
  • the provision of folic acid,
  • the energy balance of the cells,
  • fat metabolism and
  • the functions of the nerves.

In addition, the vitamin also influences the production of hormones and neurotransmitters.

Where can you find vitamin B12?

The vitamin can be found in animal foods such as meat, eggs, fish and in all dairy products. Small amounts are also contained in a few herbal products such as sauerkraut, but these are not sufficient to supply the body with the substance. With an average mixed diet in Germany, even with an ovo-lacto-vegetarian diet with milk, eggs and cheese, we consume more of the vitamin than is necessary.

How does a deficiency come about?

Our body does not produce the vitamin itself, so we have to get it from food. It is released in the stomach and bound to proteins, which then transport it. The body then absorbs it through the intestinal mucosa, while the liver stores the substance.

A deficiency occurs because those affected either do not consume enough vitamin B12 or the body cannot use it, which is often the case with diseases in the intestine. If the mucous membrane of the digestive organs is damaged, for example due to Crohn's disease or an inflammation of the stomach, it often cannot transport the vitamin. Another disturbance in the vitamin balance is caused by a lack of gastric acid, which is usually triggered by proton pump inhibitors. In this case, the vitamin can no longer be released from the diet and bound to proteins.

Unlike in industrialized countries, people in premodern societies and developing countries ingested much less or too little of the vitamin from meat. However, the deficiency has seldom reached such an extent as is the case with other pathological vitamin deficiencies (scurvy or rickets), since the rural people generally always had (and still have) access to milk and milk products.

How does a deficiency show up?

Vitamin deficiency leads to anemia (megaloblastic anemia), which in turn leads to pallor and exhaustion. Other symptoms may include a burning sensation on the tongue, numbness, an unsteady gait, and confusion (mental confusion).

Anemia causes a decrease in the number of blood platelets, which results in a decrease in white blood cells. This means a higher susceptibility to infections, because the body's own defense system weakens.

The unsafe gait is due to dysfunction of the nervous system, as well as the psychological confusion and tingling in the limbs. If the vitamin deficiency persists, even paralysis can occur.

A deficiency affects the messenger substances and nerves, which is why mental illnesses can also have long-term effects from a vitamin deficiency: depression, dementia, anxiety disorders, psychoses and hallucinations are possible.

The problem with this is that none of these symptoms are specific. All of them can have entirely different causes than a deficiency. Anemia, for example, could be the result of iron deficiency, nerve disorders can be the cause of a nerve disease, etc. - so you should not come up with the idea of ​​making an independent diagnosis. This is a matter for doctors.

When do the symptoms show up?

The vitamin deficiency develops in the long term. The liver of a healthy person usually stores the substance in an amount that meets the need for three years. So vegans should be careful: they can eat vegan for years without showing symptoms of deficiency, although they do not ensure an adequate supply of the vitamin. However, this only means that the liver draws on its supplies. The “harmless” symptoms such as fatigue already appear while the liver is emptying.

Is there an overdose?

A deficiency is not only problematic for many vitamins, because an overdose can also be harmful. With a vitamin B12 excess, there is no evidence of such damage because the body excretes unused B12. So if you do not suffer from an acute B12 undersupply, you can still take the vitamin without hesitation - it will only damage your wallet because you are paying for a superfluous product.

Ask the doctor

If you suspect a B12 deficiency, consult a doctor. Pregnant women have an increased need for vitamin B12, which they can meet by consuming meat, eggs and dairy products. Ask your gynecologist if supplements are an option.

In the case of chronic bowel diseases, you should explicitly pay attention to your B12 budget and talk to your responsible specialist about ways to get it going. If the intestinal mucous membranes do not transport the vitamin, additional vitamin preparations do not make sense, since you have sufficient amounts of the substance in the body. This also applies to a lack of stomach acid.


If the doctor asks you about your diet and / or chronic illnesses and if you suspect a deficiency, this can be proven with several tests.

The serum test shows the total amount of B12 in the blood. However, it is considered inaccurate because it also measures compounds that only resemble the vitamin. The holo-transcobalamin test is safer because it measures the usable vitamin B12, which is transported by the transcobalamin. A test of methylmalonic acid in blood or urine is also considered safe because this acid is a by-product of the vitamin B12 balance. The lower the value, the higher the deficiency.

Preventive check-up

If you are neither a vegan nor suffer from the "typical suspect", that is, diseases of the intestine, stomach or pancreas, there is no risk of a vitamin B12 deficiency. If in doubt, just eat more meat, liver or eggs. A test can easily be done with your family doctor.


A lack of the vitamin can be treated with a variety of preparations. After the diagnosis, the doctor decides whether it is suitable to increase the intake via dietary supplements or medication.

Beware of advertising promises

If you have an actual deficiency, caution should be exercised with chlorella-based supplements. These are advertised as a bio-alternative to cyanocobalamin, but only contain vitamin B12 analogues that do not work like vitamins. The basis for vitamin B12 products is usually cyanocobalamin formed by microorganisms such as propionibacteria.

The manufacturers of dietary supplements naturally have a financial interest and of course want to sell their funds. Since the supplements mentioned are not medicinal products, they must not be touted as medicines for diseases. With vitamin B12, for example, advertising phrases such as "contributes to energy metabolism" or "plays a role in the functioning of the nervous system" etc. are often added. This is not wrong, but if the suggestions go subliminally in the direction that a healthy person needs these preparations or that they also promote his "well-being", it is simply wrong. Don't throw your money out the window. (Dr. Utz Anhalt)

Author and source information

This text corresponds to the specifications of the medical literature, medical guidelines and current studies and has been checked by medical doctors.


  • Hans Konrad Biesalski, Stephan Bischoff, Matthias Pirlich et al., Nutritional Medicine, According to the nutritional medicine curriculum of the German Medical Association and the DGE, Thieme Verlag, 4th edition, 2010
  • Larry E. Johnson, Nutritional Disorders - Vitamin Deficiency, Addiction, and Intoxication - Vitamin B12, MSD Manual, (accessed June 25, 2019), MSD
  • Uwe Gröber: Medicines and micronutrients: medication-based supplementation, Wissenschaftliche Verlagsgesellschaft Stuttgart, 4th edition, 2018
  • Bruce H.R. Wolffenbuttel, M. Rebecca Heiner Fokkema, Hanneke J.C.M. Wouters, Melanie M. van der Klauw: The Many Faces of Cobalamin (Vitamin B12) Deficiency, Mayo Clinic Proceedings: Innovations, Quality & Outcomes, (available on June 25, 2019), MAYO

ICD codes for this disease: E56ICD codes are internationally valid encodings for medical diagnoses. You can find yourself e.g. in doctor's letters or on disability certificates.

Video: Vitamin B12 Digestion and Absorption (August 2022).