Is it possible to have an allergy to vitamin B12?

Cobalamin is a complex vitamin that has a long history in our body. In addition, it is one more nutrient as many others are, so it is possible that there may sometimes be allergies to vitamin B12 or some negative reactions of lesser impact. It is important to note that the body does not produce this micronutrient itself. We must acquire it ourselves, either through food or supplements. Once consumed and after it is absorbed by the body, it is stored in the liver, where it has a useful life of between 2 and 3 years.

However, the process is much longer and more complex than this, so it is possible that in some of the many steps you take until it is stored, our body may react negatively to it. When taking supplements, there are people who develop an allergic reaction to them. In most cases, the reactions are not severe and, in addition, allergies to vitamin B12 are very rare. Let us focus precisely on this point.

Functions of B12 or cobalamin in the organism

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This nutrient of vitamin B complex has a wide selection of functions in the organism.

  • First, it plays a leading role in the production of DNA and RNA.
  • Secondly, it is essential for the proper functioning of the nervous system because it is responsible for keeping the myelin sheath of nerve cells in good condition.
  • It then helps to improve the symptoms of some mental illnesses such as depression because it participates in the production of neurotransmitters.
  • It also helps to maintain the energy of the muscular system.
  • It also produces red blood cells, which oxygenate our blood.
  • And, finally – and although it fulfills other functions, we emphasize that it is essential for the organism to metabolize folic acid.

It is clear that this is necessary for our body, although it cannot always be taken without some side effect. Let’s take a closer look.

Vitamin B12 allergy – Is there any risk?

Is it possible to have an allergy to vitamin B12?

There are two population groups that need to be compulsorily supplemented with cobalamine.

On the one hand, vegan and vegetarian people, those who do not include in their diet foods of animal origin. It is important to remember that the foods rich in cobalamin are precisely of animal origin; some of them, such as tempeh, fermented soybean, contain it but in very low quantities, so it is necessary to take supplements in order not to suffer deficiency of this nutrient.

On the other hand, people with digestive tract diseases that prevent them from absorbing the micronutrient correctly. Allergic reaction may occur when taking cobalamin supplements. The truth is that this is a very rare thing, which happens on rare occasions, but there is a slight possibility.

Usually, this reaction is given in people allergic to cobalt; cobalamin contains this metal. It can also occur in people with Leber’s disease. By statistic, it is clear that individuals belonging to these two risk groups will suffer allergic reactions, as they are the ones who take the most supplements. However, this does not mean that the rest of people do not suffer from these alterations if they have to supplement themselves at some point.

Knowing exactly what supplements caused the allergic reaction is no easy task. Once you notice the symptoms that we will explain in the following section, it is best to consult with your doctor. It is he who will recommend some allergy tests to assess whether your body is correctly creating certain antibodies, known as immunoglobulin E or IgE.

Perhaps when you take the supplementation, your body will not identify them as such, but as a dangerous substance that it is beginning to defend itself against. That is, your immune system reacts incorrectly to supplements and creates these antibodies to fight them.


Symptoms of a vitamin B12 allergy are varied. It usually occurs in the vast majority of cases:

  • Persistent headache
  • Wheezing
  • Crying eyes
  • Asthma
  • Fatigue
  • Sneezing

In addition, various pathologies related to the digestive tract, such as nausea, vomiting or abdominal cramps, can develop, although it is more rare. Other warning signs such as numbness, fever, and pain may also occur.

In these cases, and as we have indicated, it is essential to go to the family doctor for a check-up or analysis and begin to rule out pathologies until we find the problem that, we repeat, does not have to be cobalamin allergy; these symptoms can be a sign of other pathologies but when several of them are given it is advisable, if the doctor does not indicate it, we propose the vitamin allergy as a possible cause.


As a treatment, it is most effective to stop taking supplements. To avoid suffering deficiency of this nutrient, which can be considered a serious pathology, you should include in your diet foods that contain it as eggs, dairy, sardines or beef, to give some examples.

Vitamin B12 deficiency – Is it considered a serious pathology?

Symptoms of vitamin B12 deficiency fatigue

Why is supplementation so important? Simply, because the deficiency of this micronutrient is a pathology that can be serious, including very important consequences such as health problems in the medium and long term. Some are as follows:

  • Nerve degeneration
  • Loss of brain mass
  • Numbness of arms and legs
  • Ulcers

The needs of B12 are covered in people with a rich and varied diet; however, these people can also take supplements, always in adequate doses, to ensure good levels of this nutrient in blood. However, there are certain patients who need supplements, yes or yes:

  • People over 50 years of age, as the body no longer absorbs nutrients well after that age.
  • People who take heartburn or epilepsy medications
  • Patients with Crohn’s disease or ulcerative colitis
  • Vegetarians and vegetarians
  • Pregnant or nursing women

In cases of need, where there are allergies to cobalamin, only a doctor will determine how to proceed, assessing the consequences of both stopping taking the supplement and the symptoms you have when consuming it. We must never leave this decision to ourselves.

Required daily amount or dosage of vitamin B12

How much cobalamin the body needs daily depends basically on age.

  • Up to 6 months: 0.4 micrograms
  • From 7 to 12 months: 0.5 micrograms
  • From 1 to 3 years: 0.9 micrograms
  • 4 to 8 years: 1.2 micrograms
  • From 9 to 13 years: 1.8 micrograms
  • 14 to 18 years: 2.4 micrograms
  • Pregnant women: 2.6 micrograms
  • Breastfeeding women: 2.8 micrograms

These are not quantities impossible to reach without supplementation. With a well-designed diet you can have an optimal level of cobalamin in your blood, so if you have allergic reactions to supplements, you can always improve your diet. The exception, as we have indicated, is for those population niches at risk that need to be forcibly supplemented.


By way of conclusion, make special emphasis on the fact that taking supplements is never a negative thing. People over 50, as well as vegans and vegetarians, can take B12 supplements. It is most commonly taken as a weekly supplement; 1 pill of 1000 or 2000 micrograms per week. For patients with a disease that does not allow their body to properly absorb the nutrients, it is best to consult with your doctor, who will be the one to tell you which is the best option.

They will need supplements that do not need to be absorbed by the body, but come into direct contact with the bloodstream, such as injections or nasal gels. In the case of symptoms following supplementation, a doctor should be advised to rule out or confirm if we suffer from allergies to vitamin B12 and, with its supervision, act accordingly.

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Did you know of any possible allergies to B12 or other supplements? Have you suffered from this one? What was your treatment? Tell us about your experiences to help the community!

If you found it helpful or have any questions, please comment and share, thank you! 😉

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