Weight gain as a side effect of vitamin B12: the most important questions and answers

Gewichtszunahme als Nebenwirkung von Vitamin B12: Die wichtigsten Fragen und Antworten

Have you suddenly gained weight and are wondering if this is a side effect of your vitamin B12 dosage? Or do you even suffer from a cobalamin deficiency? Vitamins are essential for our body, which is why you should always make sure to cover your needs.

This article is intended to answer the most important questions about vitamin B12 and its weight gain as a possible side effect. We will explain to you which tasks cobalamin takes on in your body and what happens if you take the wrong dosage. We then clarify the question of whether you gain weight because of vitamin B12 and which other factors play a role in weight change.

the essentials in brief

  • Vitamin B12 is one of the B vitamins and is also called cobalamin. It is essential for many functions in the body and can thereby prevent some diseases and symptoms.
  • Neither an overdose nor a lack of vitamin B12 can lead to weight gain. On the contrary, in the USA it is used more as a means of weight loss.
  • In order to counteract weight gain, you should eat consciously, do enough sport and avoid alcohol and cigarette consumption. However, diseases can also lead to weight changes.

Vitamin B12 - weight gain as a side effect: What you should know

In the following section we explain the tasks and functions of vitamin B12. We also look at whether cobalamin can lead to weight gain, or if this is just a myth.

What is vitamin B12 and what is its role in the body?

Vitamin B12 is also known as cobalamin and is one of the B vitamins. It is the only water-soluble substance and is stored in the body. The storage can take place in the liver for several years.

A special protein is required for the absorption of vitamin B12, the intrinsic factor. This is produced by the gastric mucosa and then enters the intestine together with the food.

Vitamin B12 is not only important for cell division and blood formation, but also for the functioning of the nervous system.

The vitamin influences a number of important body processes. By affecting energy and lipid metabolism, DNA synthesis and body detoxification, B12 can combat the following diseases and symptoms:

  • Immune deficiency and chronic diseases
  • Depression, schizophrenia, psychosis (1,2)
  • Anemia and damaged mucous membranes
  • Listlessness, poor performance and chronic fatigue (3)

Furthermore, vitamin B12 can prevent numbness, discomfort, tingling and pain as it plays a crucial role in the production of the myelin sheath in the spinal cord and central nervous system. If the myelin sheaths are destroyed due to a lack of vitamin B12, the symptoms mentioned can occur. (4)

encapsulate vitamin B

Vitamin B12 influences many tasks in the body and can thus fight several diseases. (Image source: unsplash.com / Kayla Maurais)

In addition to vitamin 6 and folic acid, vitamin B12 also causes a significant reduction in homocysteine ​​levels. The vitamins thus reduce the risk of cardiovascular disease. (5)

In addition, a study proved that vitamin B12 can be beneficial for neurodermatitis. Creams and lotions can improve your complexion a lot. (6)

Cobalamin can affect brain functions.

Another important function of cobalamin is to improve cognitive functions, especially immediate and delayed memory. The vitamin promotes brain function and thus prevents the brain from shrinking, which would lead to a loss of brain power in old age. This has a positive impact on your short-term and long-term memory performance. (7.8)

Taking vitamin B12 can also be beneficial for children. A study has shown that a lack of cobalamin in children has a negative impact on the development of their mental abilities. It is therefore more difficult for them to imagine something spatially or to perceive things in general. (9)

How much vitamin B12 should I take in a day?

The daily requirement of vitamin B12 varies from person to person. According to the German Society for Nutrition (DGE), a quantity of 4.0 micrograms of vitamin B12 per day is recommended for young people from the age of 13 and adults, depending on their age. The daily requirement of babies is around 0.5 to 1.5 micrograms, children have a daily requirement of between 1.5 and 3.5 micrograms of vitamin B12, depending on their age.

Old Vitamin B12 daily requirement
0 - 4 months 0.5 micrograms
4 - 12 months 1.4 micrograms
1 - 13 years 1.5 - 3.5 micrograms
From 13 years 4.0 micrograms

Pregnant and breastfeeding women should take a higher dose of vitamin B12. The DGE recommends a daily amount of 4.5 micrograms of B12 for pregnant women and 5.5 micrograms of vitamin B12 for breastfeeding women.

How does a vitamin B12 deficiency occur and what happens in the event of an overdose?

A vitamin B12 deficiency can occur due to low intake of the vitamin, as well as excessive consumption or loss.

An unbalanced diet can lead to a deficiency.

A vitamin B12 deficiency is widespread and can be unspecific. Risk groups include the elderly, vegetarians/vegans, pregnant women and patients with kidney or intestinal diseases. If you belong to one of the risk groups, you should definitely have yourself examined regularly every few years. (10)

A lack of cobalamin develops very slowly and insidiously. It is often only recognized after two to three years, when all reserves in the liver have been used up. However, a diagnosis is very important, since a deficiency can cause neurological and irreversible damage.

The most important triggers for a vitamin B12 deficiency are:

  • Lack of intake due to a vegan or vegetarian diet
  • Lack of the important protein called intrinsic factor
  • Chronic kidney or liver disease
  • Inflammatory bowel disease or partial removal of the bowel
  • taking certain medications
  • Chain smoking and excessive alcohol consumption

Vegetarians and vegans often suffer from a vitamin B12 deficiency because their diet is very unbalanced. You can find large amounts of cobalamin in animal products in particular. You can also find traces of the vitamin in plant foods, but these can rarely cover your daily requirement.

It is common in alcoholics that the walls of the stomach and intestines are damaged due to excessive consumption of alcohol. As a result, they are no longer able to absorb vitamin B12. Furthermore, a disturbed B12 metabolism can also occur in a chain smoker.

If you have been diagnosed with a vitamin B12 deficiency, you can usually compensate for it by changing your diet or by taking vitamin B12 supplements. These preparations can be taken as tablets, for example, or administered directly into the bloodstream, for example as an infusion.

Cobalamin overdose is very rare.

It can hardly happen that you take in too much vitamin B12, since the body does not normally absorb amounts that it does not need through the intestinal wall. Furthermore, an excess of cobalamin , in contrast to other vitamins, is excreted through the kidneys.

However, it is better not to take too high amounts of vitamin B12 so that an overdose does not put a strain on your kidneys.

Vitamin B12 next to spoon

Normally, an overdose of vitamin B12 cannot lead to further damage. (Image source: unsplash.com / Michael Longmire)

However, the following various medical conditions can lead to an overdose:

  • leukemia
  • Polycythemia vera (abnormal proliferation of red blood cells in particular, but also of white blood cells)
  • hepatitis
  • liver metastases

Too high a supply of vitamin B12 by the doctor can also occur if he has given you a dose via an injection. However, this is very rare.

Is Weight Gain a Possible Side Effect of Vitamin B12?

No, there is no weight gain due to cobalamin. In addition, weight gain is usually not a direct sign of a vitamin B12 deficiency. (11)

In some cases, weight gain can occur as a result of a disease that occurs due to vitamin B12 deficiency. One such disease would be autoimmune thyroiditis.

What are possible causes of weight gain?

Gaining weight can have several causes. It doesn't always have to be the wrong diet.

Poor lifestyle often leads to weight gain. This includes not only wrong eating habits, but also too little exercise.

However, more serious medical conditions can also cause you to gain weight. Examples of such diseases include hypothyroidism, heart failure or tumors.

In addition , taking medication can increase your weight. Some of these drugs could be antidepressants, estrogens or insulin, for example.

Mental illnesses and addictions , such as depression and excessive alcohol consumption, can also be associated with weight changes such as weight gain.

Can Vitamin B12 Help With Weight Loss?

As has already been found, weight gain is not normally a possible side effect of vitamin B12. In the following section, we take a closer look at whether cobalamin can help with weight loss.

What are vitamin B12 shots?

Vitamin B12 shots have become an absolute trend in the USA. Many celebrities, including Rita Ora and Katy Perry, are said to have tried an injection.

So far, this effect could not be proven concretely.

Vitamin B12 shots are injections or infusions through which cobalamin is injected. This can be administered not only in a highly concentrated dose, but also in smaller amounts along with other vitamins.

Does Vitamin B12 Help You Lose Weight?

On the one hand, the extra dose of the vitamin should ensure a healthy body, but on the other hand it should also accelerate the metabolism, support muscle building and performance and increase energy.

An extra portion of vitamin B12 to lose weight is not suitable for everyone. People who exercise enough and eat consciously, but need a kind of metabolic boost, can benefit from vitamin B12. That way you could lose a few extra pounds.

However, severely overweight people should not rely on the sole effect of vitamin B12, because they are not just a pound or two. If you are severely overweight, you should first have a basic understanding of a healthy lifestyle.

healthy meal

Good eating habits are an important basis for a conscious lifestyle. (Image source: unsplash.com / Jannis Brandt)

Ultimately, it comes down to developing a way of life that is best suited to the individual so that they can sustain their efforts over time. (12)

Conversely, micronutrient deficiencies are also common in weight loss diet plans. (13)

Can vitamin B12 prevent weight gain?

No. Relying solely on an extra dose of vitamin B12 is not enough to prevent weight gain.

If you want to prevent gaining weight, then you should make sure that you eat consciously and in a balanced way. It is also important to get enough exercise.

However, that doesn't mean you have to cut out sugar or calories completely.

A healthy lifestyle also includes avoiding excessive alcohol and cigarette consumption. Instead of consuming alcohol, make sure to drink enough water. This can also help you to satisfy big hunger pangs. (14)

Other factors in healthy living include optimal sleep, a safe and peaceful environment, stress-free and enjoyable activities, social connections and support, and spiritual pursuits. (15)


Vitamin B12 can affect many tasks and functions in the body, but weight gain is an exception. Cobalamin has no side effect that would lead to weight gain. Neither a deficiency nor an overdose leads to a drastic increase in your weight.

On the contrary, vitamin B12 is used in the USA to lose a few kilograms. Studies have not yet been able to prove this effect, but many famous personalities are convinced of the results.


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