Causes of vitamin B12 deficiency: the most important questions and answers

Ursachen für Vitamin B12 Mangel: Die wichtigsten Fragen und Antworten

It is not uncommon for the causes of a vitamin B12 deficiency to be ignored. Instead of examining and treating the cause of the symptoms, often only the symptoms are temporarily eliminated. However, this does not solve the problem itself. Because it causes the vitamin B12 deficiency symptoms to occur again and again.

In the following article we explain in detail which symptoms can alert you to a B12 deficiency. Furthermore, we show possible vitamin B12 deficiency causes that can trigger an undersupply.

Finally, we bring you closer to various options for treating or preventing a B12 deficiency. In this article we will provide you with extensive information so that you are informed about the most important background of the causes of a vitamin B12 deficiency.

the essentials in brief

  • From malnutrition or malnutrition to a B12 absorption disorder - the list of potential triggers for a low B12 level is long. Since the symptoms of a B12 deficiency are very unspecific, it is usually difficult to diagnose the cause.
  • In order to avoid serious consequences, however, it is necessary to determine the cause of a vitamin B12 deficiency. The medical diagnosis is made with the help of various examinations.
  • The human body can store vitamin B12 for several years. (1) As a result, deficiency symptoms only appear after years of insufficient vitamin 12 intake. This gradual progression makes it even more difficult to diagnose a deficiency.

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Vitamin B12 deficiency causes: What you should know

In the following you will find relevant background information on the potential triggers of a vitamin B12 deficiency. In the course of this, we would like to note that this article does not replace a medical visit.

If you experience the symptoms listed below, we recommend that you consult a doctor. This can check your vitamin B12 balance and help you to determine the individual cause of a deficiency.

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

As the name suggests, vitamin B12 belongs to the group of B vitamins. The special feature of B12 is that it can be stored in the human body for several years. (1) Vitamin B12 is also known under the name cobalamin. Before we explain what can trigger a B12 deficiency, we would like to briefly describe the function of this vitamin.

Vitamin B12 is essential for a variety of processes in the human body.

The main tasks include the formation of red blood cells and the construction of the sheaths of the nerve fibers. This aims to preserve the nervous system. Furthermore, vitamin B12 supports the formation of DNA, RNA and other genetic material. Finally, vitamin B12 is also necessary for the breakdown of the amino acid homocysteine. If the homocysteine ​​level is too high, the risk of cardiovascular diseases can increase. (2.3)

To put it simply: vitamin B12 is essential for human life. However, since the human body cannot produce the vitamin itself, it has to be supplied in a different way.

How much vitamin B12 do you need daily?

Depending on your age, you should consume a certain amount of vitamin B12 on a daily basis. Compared to other vitamins, the required amount of B12 is rather low. Normally, a deficiency is therefore rather rare. The German Society for Nutrition recommends the following guidelines:

Old micrograms/day
0 to 4 months 0.5l
4 to 12 months 1.4
1 to under 4 years 1.5
4 to under 7 months 2.0
7 to under 10 years 2.5
10 to under 13 years 3.5
from 13 years 4.0
pregnant women 4.5
breastfeeding 5.5


As you can see in the table above, adolescents and adults over the age of 15 should consume around 4 micrograms of vitamin B12 every day. The requirement is increased in pregnant and breastfeeding women. The simple reason for this is that the unborn child or the newborn must also be supplied with the necessary nutrients.

The vitamin can only be absorbed through diet. In the following paragraphs you will learn more about the intake of B12 through food.

Which foods provide vitamin B12?

Although the human body is able to store the B12 vitamin in the long term, regular intake is necessary. This is done through foods that contain the vitamin.

Animal products are a good source of vitamin B12. Significant amounts of B12 are found in meat, fish, seafood, eggs and dairy products. (5)

tuna on a plate

With a significant amount of 4.3 micrograms per 100 grams, tuna is a good source of vitamin B12. (Image Source: Taylor Grote / Unsplash)

However, if you want to use plant-based foods, the choice is much smaller. According to our research, it is difficult to meet the B12 requirement with a plant-based diet. (5.6)

Plant products only get the B12 vitamin through bacterial fermentation. For example, sauerkraut, beer, and seaweed are sources for vegetarians, and especially vegans. However, since the B12 content is very low and the usability cannot be guaranteed, a purely plant-based diet can be problematic. (6)

What are the symptoms of a vitamin B12 deficiency?

The symptoms of an undersupply of the B12 vitamin are very diverse. In addition, the signs in the early stages of a vitamin B12 deficiency can still be quite unspecific. Because of this, a blood test is recommended for a clear diagnosis. It should also be noted here that symptoms of deficiency can become noticeable years later.

Basically, the deficiency symptoms can be divided into neurological and physical complaints. In the initial stage, when the store is slowly being emptied, the symptoms tend to be mild to moderate.

These include, for example, weakness and tiredness, hair loss, torn corners of the mouth, mood swings, personality changes, sleep, coordination and vision disorders. (7)

woman holding her baby

In newborns, a vitamin B12 deficiency can lead to developmental disorders. Because of this, breastfeeding women should make sure they are getting enough B12. (Image Source: Wes Hicks / Unsplash)

In the advanced stage, when the B12 store is completely exhausted, severe symptoms occur. These include paralysis, spastic cramps, movement disorders, dementia or anemia. But you will learn more about this in the course of the article.

How does a vitamin B12 deficiency occur?

Compared to many other nutrients that the human body needs, the daily requirement of vitamin B12 is comparatively low. Nevertheless, a study shows that a quarter of people over 65 fail to meet their daily B12 requirements. (8th)

There are various influences that favor a vitamin B12 deficiency.

In the following paragraphs we will explain the causes of such a defect. In principle, a deficiency always occurs when the absorbed amount of the vitamin falls below the requirement. In some cases, a shortage can occur when the need is higher than the norm. This often applies to pregnant or breastfeeding women. Furthermore, an increased loss can also lead more quickly to insufficient vitamin B12 storage.

For a better overview, we have listed the most common and most important causes:

  • Malnutrition or malnutrition: Too little B12 intake is a common cause of vitamin B12 deficiency. This occurs either in vegetarians/vegans or in people with anorexia.
  • Intrinsic factor: In order to be able to absorb vitamin B12, a special protein must be present in the human body. This is also called the intrinsic factor. Those suffering from an intrinsic factor deficiency cannot actively absorb B12 in the intestine. The missing transport protein can therefore also be a decisive factor for a vitamin B12 deficiency.
  • Disturbed bowel function: The absorption of vitamin B12 can be made more difficult by, for example, chronic inflammatory bowel diseases.
  • Increased consumption : In particular, people suffering from diseases such as chronic kidney or liver diseases have to cope with higher consumption. Consumption also increases when the intestines are infested with parasites.
  • Taking medications: Medications that affect vitamin B12 balance include diabetes medications, antibiotics, antihistamines, proton pump inhibitors, and more.

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How is a vitamin B12 deficiency diagnosed?

Since the symptoms of a B12 deficiency are very unspecific, it is necessary to carry out a medical laboratory test. In order to be able to interpret the symptoms, you should have a blood and urine test carried out by a doctor of your choice.

Various laboratory values ​​can then show whether there is a deficiency or not. During the examination, the doctor looks at the vitamin B12 level, the holo-transcobalamin and the homocysteine ​​value. However, the latter is not very meaningful, since an increased homocysteine ​​value can also indicate kidney weakness or diabetes.

You should know that such examinations are usually not covered by health insurance. It is therefore best to find out in advance about the costs involved.

Who belongs to the risk group of a vitamin B12 deficiency?

A vitamin B12 deficiency can have health consequences. Especially people who belong to the risk groups should pay attention to an adequate intake of B12.

There is an increased risk for the following groups of people:

  • Vegetarians and Vegans (9)
  • people with malnutrition
  • Pregnant and lactating women
  • Elderly people
  • Individuals suffering from certain medical conditions and/or taking medication

Basically, a distinction can be made between two different types of risk groups. On the one hand, there are people who do not reach the recommended guideline value due to malnutrition or malnutrition. This includes vegetarians, vegans and people with an eating disorder.

On the other hand, there are groups of people who have an increased need and therefore have to pay additional attention to an adequate intake. The occurrence of a defect is more likely in such cases.

In the following paragraphs you will learn more about the effects of a B12 deficiency.

What are the consequences of a vitamin B12 deficiency?

If the organism does not absorb enough vitamin B12, this leads to health consequences. As we have already mentioned several times, the problem with a B12 deficiency is that it is only noticed over the course of a few years.

It is therefore recommended to have an examination carried out if there are any signs. A permanent undersupply can otherwise have serious consequences.

As soon as the B12 store is completely depleted, anemia can occur. The so-called anemia occurs because the formation of blood cells is disturbed. Furthermore, a vitamin B12 deficiency can lead to damage in the peripheral and central nervous system. This would manifest itself in paralysis and psychoneurological problems.

Since irreparable nerve damage cannot be ruled out in extreme cases, a permanent undersupply should not be underestimated. (10) Because of this, we subsequently researched possible approaches to prevent and treat a vitamin B12 deficiency for you.

How can you treat or prevent a vitamin B12 deficiency?

If you are affected by a vitamin B12 level that is too low, there are a few aspects that can counteract this. The following factors can have a positive influence on your B12 household:

  • Nutrition: A deficiency can be prevented or treated by consuming foods with a high vitamin B12 content. Since the vitamin is mainly found in animal products, foods such as meat, fish, milk and eggs should be part of the diet.
  • Avoiding alcohol, nicotine and caffeine : Drinking alcohol and smoking can promote a deficiency of the B12 vitamin. Because of this, it is recommended to keep alcohol and drug consumption as low as possible. In addition, no more than four cups of coffee should be consumed daily, as this can have a negative effect on the B12 household.
  • Stress reduction: Those who are constantly under stress have a higher need for vitamin B12. The usual amount is no longer sufficient for a balanced B12 household. You should therefore minimize stress on the one hand and increase the dose of B12 in your diet on the other to meet consumption.
  • Dietary supplements: The intake of vitamin B12 in the form of dietary supplements is usually only necessary if there is an increased need or if there is a deficiency caused by a disease, such as chronic intestinal inflammation. You can alternatively choose between B12 tablets, capsules, sprays or drops.
  • Recovery cure: In the case of an acute B12 deficiency, only a recovery cure can usually help. Similar to the dietary supplements, you get extra B12 here. This is administered via infusions.


In order to find out the cause of a vitamin B12 deficiency, it is necessary to first recognize the deficiency as such. The many different symptoms that can indicate an undersupply do not necessarily indicate a vitamin B12 deficiency.

The problem with this is that it is difficult to make an unambiguous determination. Since a deficiency can only become noticeable over the course of a few years, it is difficult to make an early diagnosis. With the help of medical examinations, however, one can approach a finding.

Once you have identified a vitamin deficiency, it is important to find out the cause. This is necessary to counteract undersupply in the long term. The most common causes include insufficient intake or intake or an increased need for the B12 vitamin. In such cases, a rebuilding cure or the supply of B12 by means of dietary supplements should finally be initiated.

Otherwise, neurological damage can occur. In summary, it can be said that the causes of the diagnosis of a B12 deficiency should not be underestimated, since the vitamin plays an essential role in the human body.


  1. Donald S McLaren. The luxury vitamins-A and B12 Am. J.Clin. nutr. 34:161 1-1616, 1981.
  2. Wald, DS, Law, M, & Morris, JK (2002). Homocysteine ​​and cardiovascular disease: evidence on causality from a meta-analysis. BMJ (Clinical research ed.), 325(7374), 1202.
  3. Fanapour, PC, Yug, B, & Kochar, MS (1999). Hyperhomocysteinemia: an additional cardiovascular risk factor. WMJ: official publication of the State Medical Society of Wisconsin, 98(8), 51-54.
  4. German Society for Nutrition eV, reference values ​​​​of vitamin B12 according to age
  5. Watanabe, F., & Bito, T. (2018). Vitamin B12 sources and microbial interaction. Experimental biology and medicine (Maywood, NJ), 243(2), 148-158.
  6. German Society for Nutrition eV, position on purely plant-based nutrition
  7. Lukaski H.C. (2004). Vitamin and mineral status: effects on physical performance. Nutrition (Burbank, Los Angeles County, Calif.), 20(7-8), 632-644.
  8. Conzade R, Koenig W, Heier M, Schneider A, Grill E, Peters A, Thorand B. Prevalence and Predictors of Subclinical Micronutrient Deficiency in German Older Adults: Results from the Population-Based KORA-Age Study. nutrients. 2017; 9(12):1276.
  9. Lederer, AK, Hannibal, L., Hettich, M., Behringer, S., Spiekerkoetter, U., Steinborn, C., Grünemann, C., Zimmermann-Klemd, AM, Müller, A., Simmet, T., Schmiech, M., Maul-Pavicic, A., Saturday, Y., & Huber, R. (2019). Vitamin B12 Status Upon Short-Term Intervention with a Vegan Diet-A Randomized Controlled Trial in Healthy Participants. Nutrients, 11(11), 2815.
  10. McCombe, PA, & McLeod, JG (1984). The peripheral neuropathy of vitamin B 12 deficiency. Journal of the neurological sciences, 66(1), 117-126.
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