Everything you need to know about vitamin B12


Vitamin B12 is a crucial B vitamin. It is needed for nerve tissue health, brain function, and the production of red blood cells. Cobalamin is another name for vitamin B12.

Deficiency can result when levels of vitamin B12 are too low. This can lead to irreversible neurological symptoms. In the United States (U.S.), between 1.5 and 15 percent of the population are currently diagnosed with vitamin B12 deficiency.

This article will explore the functions of vitamin B12, how a person would know they are not consuming enough vitamin B12, and where to source more.

Fast facts on vitamin B12

  • Vitamin B12 is important for brain function the synthesis of red blood cells.
  • Deficiency of vitamin B12 can lead to neurological difficulties and anemia.
  • People over the age of 14 should consume more than 2.4 micrograms (mcg) of vitamin B12 daily.
  • Vitamin B12 is naturally available in meats, but people who do not eat meat, such as vegans, can obtain vitamin B12 in supplement form.

What is vitamin B12?

Vitamin B12 is a water-soluble vitamin, like all other B-vitamins.

This means it can dissolve in water and travel through the bloodstream. The human body can store vitamin B12 for up to four years. Any excess or unwanted vitamin B12 is excreted in the urine.

Vitamin B12 is the largest and most structurally complicated vitamin. It occurs naturally in meat products and can only be industrially produced through bacterial fermentation synthesis.


Vitamin B12 can be found naturally in animal products, such as fish, meat, eggs, and dairy products. It does not typically occur in plant foods.

Good dietary sources of vitamin B12 include:

  • beef
  • pork
  • ham
  • poultry
  • lamb
  • fish, especially haddock and tuna
  • dairy products, such as milk, cheese, and yogurt
  • some nutritional yeast products
  • eggs

Some types of soya milk and breakfast cereals are fortified with vitamin B12.

It is always better to maintain a balanced diet and receive healthful amounts of nutrients before active treatment is required. The symptoms of deficiency are easily avoided with a healthful diet.


Vitamin B12 is crucial to the normal function of the brain and the nervous system. It is also involved in the formation of red blood cells and helps to create and regulate DNA.

The metabolism of every cell in the body depends on vitamin B12, as it plays a part in the synthesis of fatty acids and energy production. Vitamin B12 enables the release of energy by helping the human body absorb folic acid.

The human body produces millions of red blood cells every minute. These cells cannot multiply properly without vitamin B12. The production of red blood cells reduces if vitamin B12 levels are too low. Anemia can occur if the red blood cell count drops.

Intake requirements

In the U.S., the National Institutes of Health (NIH) recommend that teens and adults over the age of 14 years should consume 2.4 micrograms (mcg) of vitamin B12 a day. Pregnant women should be sure to consume 2.6 mcg, and lactating women 2.8 mcg.

Excessive intake of vitamin B12 has not demonstrated toxic or harmful qualities. However, people are always advised to speak with their physician before starting to take supplements.

Some medications may interact with vitamin B12. These include metformin, proton pump inhibitors, and h2 receptor agonists, often used for peptic ulcer disease. All of these drugs may interfere with vitamin B12 absorption. The antibiotic chloramphenicol, or chloromycetin, may also interfere with red blood cell production in people taking supplements.

Deficiency symptoms

Vitamin B12 deficiency occurs when the body does not receive enough vitamin B12.


It can result in irreversible and potentially severe damage, especially to the nervous system and brain.

Even slightly lower-than-normal levels of vitamin B12 can trigger deficiency symptoms, such as depression, confusion, memory problems, and fatigue. However, these symptoms alone are not specific enough to diagnose vitamin B12 deficiency.

Other symptoms of vitamin B12 deficiency include constipation, loss of appetite, and weight loss.

Once symptoms escalate, they can include neurological changes, such as numbness and tingling in the hands and feet. Some people may have difficulty maintaining balance.

Infants who lack vitamin B12 may demonstrate unusual movements, such as face tremors, as well as reflex problems, feeding difficulties, irritation, and eventual growth problems if the deficiency is left untreated.

Vitamin B12 deficiency carries a serious risk of permanent nerve and brain damage. Some people with insufficient vitamin B12 have a higher risk of developing psychosis, mania, and dementia.

Insufficient vitamin B12 can also lead to anemia. The most common symptoms of anemia are fatigue, shortness of breath, and an irregular heartbeat. People with anemia might also experience:

  • a sore mouth or tongue
  • weight loss
  • pale or yellowing skin
  • diarrhea
  • menstrual problems

Vitamin B12 deficiency also leaves people more susceptible to the effects of infections.

Who is at risk?

Vegans face a risk of vitamin B12 deficiency, as their diet excludes animal-sourced food products. Pregnancy and lactation can worsen deficiency in vegans. Plant-sourced foods do not have enough cobalamin to guarantee long-term health.

People with pernicious anemia may lack vitamin B12. Pernicious anemia is an autoimmune disease that affects the blood. Patients with this disorder do not have enough intrinsic factor (IF), a protein in the stomach that allows the body to absorb vitamin B12.

Other at-risk groups include people with small intestine problems, for example, an individual whose small intestine has been surgically shortened. They may not be able to absorb cobalamin properly. People with Crohn’s disease are said to be at risk, but researchers maintain that there is a lack of evidence to confirm this.

Gastritis, celiac disease, and inflammatory bowel disease may lead to a deficiency because these conditions cause the absorption of nutrients to be reduced.

People with chronic alcoholism may lack vitamin B12, as their bodies are also not able to absorb nutrients efficiently.

Individuals treating diabetes with metformin are advised to monitor their levels of vitamin B12. Metformin might reduce the absorption of vitamin B12.

Treatment includes vitamin B12 injections. A vitamin B12 injection must be administered to people that have problems with nutrient absorption.


Some people have difficulties absorbing vitamin B12 from food sources and may need to take supplements.

This includes older adults, patients with pernicious anemia, and those with achlorhydria or intestinal disorders may have problems absorbing vitamin B12 from food.

Supplements can be taken orally or in a nasal spray. However, oral supplements do not help in many cases of deficiency. In these circumstances, vitamin B12 may be injected.

Vegans can take supplements to avoid deficiency, as the vegan diet remove the meat products that provide B12 naturally. This is particularly important during pregnancy and while breastfeeding.

Side effects

The side effects of taking vitamin B12 are very limited. It is not considered to be toxic in high quantities, and even 1000-mcg doses are not thought to be harmful.

There have been no reports of an adverse reaction to B12 since 2001 when a person in Germany reported rosacea as a result of a B12 supplement. Cases of B12-triggered acne have also been reported.

Cyanocobalamin is an injectable form of the supplement that contains traces of cyanide, a poisonous substance. As a result, some concerns have been raised about its possible effects. However, many fruits and vegetables contain these traces, and it is not considered a significant health risk.

This type of supplement is not, however, recommended for people with kidney disease.


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