October 10, 2025, 2:17 am | Read time: 12 minutes

Vitamin B12 (also called cobalamin) is unique because it cannot be produced by the body, yet it can be stored there long-term. It performs vital functions in the formation of red blood cells, DNA, and the nervous system. A deficiency is therefore dangerous, as it can lead to nerve damage and symptoms such as anemia. Those most affected are older people and vegans, as B12 is primarily found in animal products. In these cases, it may be sensible to take Vitamin B12 as a dietary supplement.

What

Vitamin B12 is not a single vitamin. Rather, it is a water-soluble group of vitamins known as “cobalamins” that occur in almost all living organisms. They owe their name to the common central atom, cobalt. The so-called adenosylcobalamin and methylcobalamin are the bioactive forms. The other inactive storage forms are hydroxocobalamin (Vitamin B12b) and aquacobalamin (Vitamin B12a). The former is found in foods, and the latter acts as an intermediate in the body. Except for the latter, all three vitamin compounds are approved as dietary supplements in Germany according to EU regulations, with most supplements using cyanocobalamin, which is produced by microorganisms or synthesized in the lab.¹

Beware of False Promises

Algae-based alternatives, such as Spirulina products (e.g., Chlorella) or AFA algae, are not reliable B12 sources. These typically contain vitamin analogs that lack vitamin efficacy and are referred to as “pseudovitamins” because they are not usable by humans.² Additionally, these products do not contain as much Vitamin B12 as they claim. A food product can only advertise its Vitamin B12 content if 100 grams of the food contain at least 0.375 µg of B12 (about 15 percent of the nutrient reference value).³

According to the “Health Claims” regulation, statements regarding Vitamin B12 on products may only refer to the maintenance of normal bodily functions:

• Vitamin B12 contributes to normal energy metabolism
• Vitamin B12 contributes to normal nervous system function
• Vitamin B12 contributes to normal psychological function

Misleading claims, such as promises of more energy, better cognitive abilities, and good sleep, are not allowed.⁴

How Does B12 Work in the Body?

Although humans have bacteria that can produce Vitamin B12, the absorption of B12 occurs in the small intestine. Because the bacteria reside in the large intestine, the produced vitamin is unusable by our bodies. Therefore, we rely on intake through food or supplements. The unique aspect is that humans can store two to five milligrams of B12 in the liver and kidneys and can even reuse a large portion of it.

When inactive forms of B12, such as 5-deoxyadenosylcobalamin and methylcobalamin, are ingested, they must first be released by stomach acid and digestive enzymes and converted into corresponding active precursors, known as coenzymes. For absorption, a helper substance produced in the gastric mucosa, the so-called “intrinsic factor,” is necessary. This transports the vitamin to the small intestine cells, from where it enters the blood and nerves.

Once there, Vitamin B12 takes on important tasks. These include the formation of red blood cells and nerve fibers, as well as supporting cell growth and division.

Attributed Effects on Health and Performance

Essentially, Vitamin B12 supplementation is about preventing a deficiency and its corresponding symptoms, as well as maintaining basic bodily functions.

Maintaining Energy and Vitality

Vitamin B12 plays a crucial role in the body’s energy production. It is involved in the conversion of carbohydrates, fats, and proteins, as well as in the activation of folic acid. A deficiency can therefore lead to fatigue, weakness, and dizziness. This can be improved through supplementation, although these symptoms can naturally have many other causes.

Improvement of Neurological Functions

Vitamin B12 is also involved in the formation of the myelin sheath, which protects nerve fibers and enables the transmission of nerve impulses. Supplementation can thus support or even improve cognitive function and the nervous system and should be considered for symptoms such as tingling and burning, balance and gait instability, and an increased tendency to fall. However, the exact mechanism of Vitamin B12 on neurological function is complex and not yet fully understood, although there are initial indications of a connection between Vitamin B12 deficiency and neurological disorders such as memory problems, dementia, and peripheral neuropathy.^5,6 It is important to note, however, that not all of these neurological disorders are directly related to a Vitamin B12 deficiency. Moreover, the effects of Vitamin B12 supplementation on neurological diseases are still being studied.

Improvement of Mood and Mental Health

Since Vitamin B12 is involved in the production of neurotransmitters, it can also influence mood and mental health to some extent. A deficiency in Vitamin B12 is associated with mood swings, decreased performance, forgetfulness, depression, and anxiety, although these symptoms are naturally multifactorial.⁷

Reducing the Risk of Cardiovascular Diseases

Vitamin B12 is often associated with the reduction of homocysteine, as it is involved in its conversion to methionine. Homocysteine is an amino acid whose elevated levels in the blood are linked to an increased risk of cardiovascular diseases. The exact mechanism of Vitamin B12 in relation to the reduction of homocysteine is complex, and further studies are needed to fully understand the connection. However, it is important to note that Vitamin B12 supplementation alone may not be sufficient to lower homocysteine levels. Other factors, such as the intake of folic acid and Vitamin B6, also play a role.⁸

Who Might Benefit from Vitamin B12 Supplementation

In Case of a Deficiency

A B12 deficiency is relatively rare in the average person due to storage and a Western diet rich in animal products. However, this also means that a deficiency may not become apparent until years after it begins, as the symptoms are not always easy to diagnose. If the deficiency is detected early enough, some damage can be reversed. However, if the consequences of the deficiency are too advanced, especially nerve damage may not be repairable.

Symptoms of a Deficiency Include

• Sensory disturbances up to paralysis
• Burning tongue
• Tingling in arms and legs
• Balance issues, increased tendency to fall
• Muscle weakness
• Fatigue, concentration difficulties
• Headaches
• Depression
• Confusion
• Hair loss
• Anemia

Also interesting: Blood, Hair–These Vitamin Self-Tests Are Useless!

Who Is at Increased Risk for a B12 Deficiency?

Those who follow a vegetarian diet can obtain sufficient amounts of Vitamin B12 through dairy products and eggs, although vegetarians still tend to have a lower B12 status. The German Nutrition Society (DGE) recommends that vegans take Vitamin B12 supplements continuously, as studies show they consume less than one µg per day, which is significantly too little. Pregnant and breastfeeding women, especially if they follow a vegetarian or vegan diet, are also advised by the DGE to supplement or at least undergo testing due to the increased B12 requirement.

But older people over 65 often suffer from impaired Vitamin B12 absorption, as the efficiency of the gastrointestinal tract decreases with age. Generally, people with gastrointestinal diseases, such as gastritis or Crohn’s disease, need to be particularly careful, as they often lack the aforementioned “intrinsic factor.” Additionally, certain medications, such as proton pump inhibitors or metformin, which are administered to ten percent of diabetics, can worsen vitamin supply. The same applies to people with high alcohol consumption, and finally, people with kidney disease should also monitor their B12 status, as storage may be impaired.

For athletes and people with intense training, supplementation may be beneficial, as intense physical activity can increase the need for Vitamin B12, but it is not strictly necessary.

How Do I Find Out if Supplementation is Right for Me?

The diagnosis is made by a doctor through a blood test, where several parameters should be measured before drawing conclusions about the B12 status. This includes at least one status marker, such as serum Vitamin B12, and a functional marker (e.g., methylmalonic acid or homocysteine), and only then, if recommended by a doctor, should those affected take vitamin supplements!

An option for diagnostics is the “early detection test for Vitamin B12 deficiency.” According to the IGeL Report 2020, this is one of the 20 most frequently mentioned self-pay services. However, there is not enough data to prove the benefit of early detection testing and subsequent Vitamin B12 supplementation. Even with the preventive administration of Vitamin B12 supplements without prior Vitamin B12 determination, the data is sparse, although it is clear that potential harm is also rather unlikely. However, those who belong to a risk group should definitely undergo testing, which is even covered by insurance.⁹

In What Form Is B12 Taken or Administered?

In addition to the classic dietary supplements in capsule or powder form, there are also intravenous and sublingual forms of administration, such as injections and lozenges. These are necessary for people who cannot produce the “intrinsic factor” in sufficient quantities, as dietary supplements do not guarantee a reliable supply. Lozenges and fortified toothpaste are relatively expensive and are not covered by health insurance.¹⁰

Training and Supplementation–What to Watch Out for

Endurance athletes or people who undergo strenuous training sessions can benefit from adequate Vitamin B12 intake. However, it should also be emphasized that a balanced diet rich in natural sources of Vitamin B12 should be preferred, and if supplemented, the recommended dosage should be observed. In general, intake should only occur in consultation with a doctor or nutritionist to adjust the dosage according to individual needs and health status.

When Not to Take Dietary Supplements

In most cases, Vitamin B12 supplementation is safe and well-tolerated unless there is an allergy or intolerance to the ingredients of the dietary supplement. In any case, consulting your doctor is recommended.

Possible Risks, Side Effects, and Interactions With Medications

Generally, Vitamin B12 supplementation is safe, and side effects are rare. However, high doses can cause gastrointestinal issues. The Federal Institute for Risk Assessment suggests a maximum amount of 25 µg per day in dietary supplements.¹¹

Harmful effects from an overdose are not known to date, as it is assumed that excess Vitamin B12 is excreted or not absorbed by the body. However, two studies showed a connection between very high daily doses (more than 55 µg) and lung cancer risk.¹²

In this article from our colleagues at BILD, you will find the top-selling Vitamin B12 supplements reviewed.

Recommended Dosage

The German Nutrition Society (DGE) recommends that adults consume four micrograms of cobalamin daily through food. Due to the increased need, pregnant women should consume 4.5 and breastfeeding women 5.5 micrograms per day. For people in the aforementioned risk groups, some researchers even recommend up to 6 µg.¹³

More on the topic

Not Just Vegans Affected Symptoms of Vitamin B12 Deficiency and How to Address Them

The Best Supplements for Endurance and Performance

Getting Vitamin B12 Through Diet

Since it is very easy to meet your vitamin needs through food, this should always be preferred over supplementation.

These Foods Are Rich in B12

Animal foods are particularly rich in Vitamin B12. The reason for this is that only bacteria can produce Vitamin B12, which are either present in the animal (keyword: gut flora) or are absorbed through its food, as the bacteria are found on the ground and adhere to plants.

Foods That Provide a Lot of B12

• Offal
• Liver
• Muscle meat
• Fish
• Seafood
• Milk
• Cheese
• Eggs

As mentioned earlier, some sea algae can have a high Vitamin B12 content. Shiitake mushrooms also provide cobalamin, although the amounts contained can vary greatly. Sauerkraut or fermented soy products like tempeh also contain traces of the vitamin. However, these are not sufficient to ensure supply. Additionally, it is still unclear to what extent this form can be absorbed by humans. Even if vegans rely on Vitamin B12-fortified foods, it is not enough to meet the recommended amount.

Conclusion

Vitamin B12 is essential for cell division, blood formation, nerve function, and energy metabolism, and thus for overall health and performance. Adequate intake is therefore important to avoid a deficiency. This is usually ensured through a balanced diet, with exceptions possibly being pregnant women, vegans, competitive athletes, and people with certain conditions. To be on the safe side, regular status checks and consultation with a doctor or nutritionist are recommended in these cases. Furthermore, prescribed dosages should be adhered to, and the quality of the supplement should be considered.