15 Signs and Symptoms of Vitamin B12 Deficiency

Vitamin B12 is a vital nutrient that is required for the production of oxygen-carrying red blood cells in our body.

It is necessary for DNA synthesis and for the proper functioning of the nervous system.

Vitamin B12 has innumerable other functions from maintaining the health of skin and hair to improving memory and cognition.

Vitamin B12 and Your Diet

Foods Rich in Vitamin B12

Unlike many other nutrients that are synthesized in our body, vitamin B12 has to be consumed from your diet. This water-soluble vitamin is naturally found in animal foods making it difficult for vegetarians and vegans to get an adequate supply of this nutrient.

Milk and dairy products may still be able to supply vegetarians with some vitamin B12. But the most high-grade sources of vitamin B12 are beef liver and clams. Chicken, fish, and eggs are other great sources of B12.

Vegans can resort to vitamin B12 fortified foods or Vitamin B12 dietary supplements to ensure they get enough B12. But despite having a diet with adequate B12 intake, many people may still find themselves deficient in this important vitamin.

This is because many factors can interfere with vitamin B12 absorption making it difficult for the body to get the amount it needs for its daily B12 requirements. Elderly people have a higher risk of vitamin B12 deficiency as their ability to absorb it gets reduced.

15 Signs of Vitamin B12 Deficiency

The symptoms of vitamin B12 deficiency arise mostly due to the lack of healthy blood cells that are required for transporting oxygen to all your body cells.

This lack of B12 can lead to many physical and psychological problems. Though fatigue and weakness are the most common symptoms, there are many other sneaky symptoms to watch out for.

Pale or Jaundiced Skin

Vitamin B12 deficiency usually takes time to develop and the symptoms appear gradually and intensify over time. Because of the nature of the symptoms, it can be quickly overlooked or mistaken for something else. One of the symptoms that shows up in people with this deficiency is pale skin. They may also have a slight yellow tinge to the skin and whites of the eyes (1).

Vitamin B12 is extremely important to the human body because of the role it plays in making red blood cells, nerves, and DNA. Instructions for building the cells remain incomplete and the cells are not able to divide when there isn’t sufficient vitamin B12. This results in a type of anemia called megaloblastic anemia, in which the red blood cells remain large and weak.

Owing to the large size of these red blood cells, they are unable to pass from the bone marrow into the bloodstream for circulation. This is the reason for the lowered count in red blood cells and the resultant pale skin.

The liver breaks down these weak and fragile red blood cells more quickly than regular red blood cells. This results in increased bilirubin in the blood. The excess bilirubin in the bloodstream adds to the characteristic yellow skin and eyes that is associated with jaundice (2).

Summary: Vitamin B12 deficiency results in low red blood count causing Megaloblastic Anemia. This results in pale and jaundiced skin.

Weakness and Fatigue

Vitamin B12 is often called the “Energy Vitamin” because a deficiency usually leads to tiredness and lethargy. Weakness and fatigue are commonly experienced when there is a reduction in red blood cells that help sufficient oxygen to be transported through the whole body (3, 4).

The depleted levels of red blood cells caused by low amounts of vitamin B12 prevent enough oxygen from being transported through the body and this results in tiredness and fatigue. Many people may ignore this symptom because it is associated with so many other health problems and they often neglect being tested for this deficiency.

This symptom by itself may not be sufficient in diagnosing a B12 deficiency. However, it may be time to consult a doctor if you’ve been experiencing a lack of energy for several weeks along with signs of confusion.

Summary: The body is not able to produce enough red blood cells to transport oxygen throughout the body which causes tiredness and fatigue.

Nerve Damage Causing Paresthesia

A long term effect and a more severe symptom of vitamin B12 deficiency in the body is nerve damage. Myelin is a fatty substance that acts as a protection and insulation around the nerves and a lack of vitamin B12 halts its production (5).

An uncomfortable prickly sensation is experienced when the absence of B12 affects myelin production. This abnormal sensation that is experienced is called Paresthesia.

The most common areas of this prickly sensation are the nerves in the hands and feet, called the peripheral nerves. This symptom can have many causes and is not limited to deficient vitamin B12 (6).

Summary: Vitamin B12 is essential for the production of myelin which plays a vital role in the functioning of the nervous system. A tingling or prickly sensation may be a sign of nerve damage caused by B12 deficiency.

May Affect Your Balance And Coordination

When this deficiency is left undiagnosed or untreated, there can be significant damage to the nervous system which can also affect the way one walks or moves.

The impact it can have on your balance and coordination can make you prone to falling.

This symptom is especially more commonly seen in people over the age of 60 since vitamin B12 deficiency is more prevalent in them. Detection and reliable treatment have been known to make a significant improvement in deficiency-related disability (7).

Although uncommon, this symptom can also be seen in the young if deficiency is severe and left undiagnosed for an extended period of time (8).

Summary: Long term vitamin B12 deficiency can result in damage to the nervous system and affect balance and coordination.

Glossitis and Mouth Ulcers

One of the oral symptoms of B12 deficiency is an inflamed tongue also known as glossitis. This results in changes in the color and shape of the tongue. The buds on the tongue stretch out and disappear which gives a smoothness to the tongue.

These are usually early signs of vitamin B12 deficiency. It makes eating and speaking difficult because glossitis is painful and makes the tongue red and swollen (9).

This can sometimes be accompanied by other oral symptoms like mouth ulcers, prickly feelings of the tongue or burning or itching in the mouth (10).

Summary: Oral symptoms like a red swollen tongue may be an early sign or indication of vitamin B12 deficiency. Mouth ulcers, feelings of pins and needles in the tongue, or an itching sensation in the mouth may also occur as a result of this.

Breathlessness and Dizziness

A person with vitamin B12 deficiency-induced anemia will find it difficult to exert themselves even slightly and may experience shortness of breath and dizziness on doing so.

This happens because the body is running low on red blood cells and cannot supply the required oxygen needed by the cells (11, 12).

Due to the generic nature of this symptom, you should speak to your doctor to determine the exact cause of any unusual breathlessness.

Summary: Anemia caused by vitamin B12 deficiency results in a reduced capacity of the blood to transport oxygen needed by the body. A person may experience breathlessness and dizziness due to this.

Blurred Vision

One of the symptoms of the insufficiency of vitamin B12 is the blurring of vision. This usually occurs when vitamin B12 is not replenished and the nervous system damage that ensues leads to the defect of the optic nerve.

The optic nerve leads to the eye and hence can cause impaired vision. The damage can move to the brain resulting in a condition called optic neuropathy where the signal between the eye to the brain is disrupted.

This condition sounds frightening but is mostly reversible and can be treated by supplementing vitamin B12 (13).

Summary: Untreated B12 deficiency can sometimes lead to damage to the optic nerve and the signal between the eye and brain gets affected. This causes disturbed vision.

Mood Changes

Changes to moods are often reported in people with this deficiency. Depression and dementia are also linked to low levels of vitamin B12 at times (14, 15).

Vitamin B12 is useful in breaking down homocysteine which is a brain chemical. In fact, there is a  hypothesis that high levels of homocysteine, which is a common amino acid in your blood, can disturb signals from and to the brain. It can also cause a shortage of neurotransmitters that act like chemical agents that alter mood and control emotions. This ultimately leads to depression (16).

However, it is of great importance to be aware that depression and dementia have several other causes and must be assessed and determined by a doctor.

Adding vitamin B12 through food or a supplement may improve mood in certain people with this deficiency. This does not substitute other proven alternative medical therapies that have been known to help with depression and dementia.

Summary: Some people with Vitamin B12 deficiency show signs of dementia due to a decline in brain function. They may also show typical signs of depression and mood changes.


A lack of vitamin B12 is seen to result in a fever occasionally. An intramuscular injection of vitamin B12 reduces the temperature. Although it is still unclear as to why this happens, recovery has been noted when intramuscular vitamin B12 injection has been given (17, 18).

However, since a fever is a commonly found symptom along with a myriad of health issues, it can be easily overlooked by physicians in pursuit of the root cause. But if the high temperature does happen to be due to this deficiency, it can help avoid many costly and unnecessary investigations and antibiotic consumption.

At the same time, it is important to note fever is commonly caused by illness and not due to low levels of vitamin B12.

Summary: In extremely rare cases, vitamin B12 deficiency can cause high body temperature. The cause is still unknown.

Fast Heart Rate

Occasionally, low levels of vitamin B12 can lead to an elevated heart rate. This happens when the heart starts to combat low levels of red blood cells in the body by beating faster. The body is pushed to generate a higher volume of blood around the body and that too quickly.

The body responds by trying to ensure that sufficient oxygen circulates through all of the body’s systems to reach all the organs. Adding vitamin B12 supplements has shown improvement in heart rate in some people (19).

Summary: To make up for the less number of red blood cells caused by B12 deficiency, the heart tries to beat faster to pump more volume of blood throughout the body.

Problems with Reasoning

Vitamin B12 deficiency is also known to cause cognitive impairment or problems with thinking. You may find yourself having trouble with reasoning and memory loss. Low levels of oxygen that is reaching the brain may be the cause of these symptoms (20).

Some studies have even gone on to link low levels of vitamin B12 with Alzheimer’s disease, vascular dementia and Parkinson’s. A small segment of these cases with dementia has seen a positive change with vitamin B12 therapy which is inexpensive and safe (21).

There is a need for more research to establish this connection, but it is safe to say that vitamin B12 cannot be seen as a treatment option for every neurodegenerative disease. It is best to get yourself evaluated by a physician before jumping to any conclusions.

Summary: Low B12 causes less oxygen to be circulated to the brain which causes some problems with thinking and reasoning in the individual.


Some people with low vitamin B12 have shown general irritability along with certain mood changes (22).

Although there is not enough research on the impact of vitamin B12 deficiency on mental health, the theory about vitamin B12’s role in breaking down the brain chemical homocysteine indicates that high levels of homocysteine can lead to a shortage of neurotransmitters that in turn control mood changes (23).

This may ultimately cause irritability and other mood disorders. There may be several other causes for mood changes like irritability and should not be used to diagnose a deficiency without other symptoms.

Summary: A person with low vitamin B12 may have high levels of homocysteine which is a  brain chemical responsible to control mood changes. This may result in signs of irritability.

Nausea and Vomiting

Vitamin B12 deficiency can also cause problems with the digestive tract. These may include nausea, vomiting, heartburn, bloating, constipation or diarrhea.

Low levels of red blood cells mean not enough oxygen is being transported to the gut where the digestion process takes place. And insufficient oxygen can cause disturbance to the digestive tract causing the person to feel sick.

Summary: Insufficient vitamin B12 can cause digestive issues due to less oxygen being sent to the gut.

Decreased Appetite

Due to the digestive issues in some people with this deficiency, there is a constant feeling of nausea which decreases the desire to eat (24).

This loss of appetite is often ignored or passed off under another sickness and not linked with this deficiency. It is important to note that loss of appetite alone cannot help in diagnosing without other symptoms (25).

Summary: In some people with vitamin B12 deficiency, it is noted that there is a decreased appetite possibly due to the nausea.

Weight Loss

Reduced appetite results in unintentional weight loss in some people with insufficient vitamin B12. This symptom alone is not enough to determine whether or not a person is deficient, because of its generic nature.

Some elderly people who have undergone gastric surgery are more prone to get this symptom and deficiency (26).

Summary: Low levels of vitamin B12 sometimes causes nausea and loss of appetite which results in weight loss in the individual.

6 Causes of Vitamin B12 Deficiency

Vitamin B12 deficiency may occur for the following reasons:-


Vitamin B12 is absorbed into our body through the foods we eat. Following a vegan diet that is devoid of nutrients from food sources such as meat, milk, cheese, and eggs. Vegetarians and vegans may require B12 supplementation if their intake of vitamin B12-fortified food grains is inadequate.

Some of the most affected are nursing babies of vegetarian and vegan mothers because they do not get enough of this essential nutrient. Pregnant women who do not consume animal-based foods may not be providing enough vitamin B12 to their unborn babies.

Pernicious Anemia

People suffering from pernicious anemia, a condition where the intrinsic factor required to absorb vitamin is not produced in the body.

This is usually treated with vitamin B12 injections or high doses of oral supplements.

Aging and Reduced Absorption

Some people have trouble absorbing this vital vitamin from food sources. It affects approximately 15% of the population.

Older adults and people over 50 years of age may not produce enough hydrochloric acid in the stomach. This is necessary for the absorption of the vitamin.

Gastrointestinal Surgery

Those who have undergone gastrointestinal surgery or have digestive disorders reduce the capacity to draw in this essential nutrient.

Autoimmune Diseases

Thining of the stomach linings due to atrophic gastritis or having other immunity disorders like Crohn’s and Celiac disease, Graves, Lupus, etc. can cause your body to mistakenly attack healthy stomach cells.

They also attack a glycoprotein known as the gastric intrinsic factor which is responsible for the absorption of vitamin B-12.

Drug Interactions

Some medications you take may impede the absorption of vitamin-B12. This includes drugs such as metformin, colchicine, anti-seizure medications such as primidone, antibiotics like neomycin or gentamicin, extended-release potassium products and heartburn medications such as omeprazole or cimetidine.

Taking the supplement and such drugs at different times of the day may reduce these interactions and improve your vitamin B12 absorption.

Summary: Several causes may be attributed to the lack of vitamin B12 in the body. An early check of this vital nutrient’s level in the body will increase the body defense against diseases.

Treatments for B12 Deficiency

On average, most people can get sufficient vitamin B12 from dietary sources. Treatment will vary based on whether the deficiency is caused by diet insufficiency or if it is causing any neurological problems in the individual.

Those who are not able to get enough through diet and are diagnosed with a B12 deficiency may be prescribed by a doctor to take a supplement in the form of tablets during the day. People following a strict vegan diet may find it difficult to get enough vitamin B12 through their regular diet and may need supplementation for life (27, 28).

Vitamin C may interfere with the absorption of vitamin B12 when consumed together. It is best to avoid taking large doses of vitamin C within one hour of taking the supplement. There has also been another study that suggests that vitamin C ingestion helps prevent vitamin B12 deficiency. If you must consume vitamin C, please do it at another time from when you choose to have B12 supplements (29).

More severe forms of anemia or people having trouble absorbing this nutrient may need treatment through vitamin B12 injections. The frequency and dosage will need to be monitored through regular follow-ups to ensure that absorption is taking place.

Summary: Ideally, the vitamin B12 needs of a person must be met through a wholesome diet. Supplements in the forms of tablets or injections can be taken under a doctor’s guidance when this is not met.

The Final Note

Vitamin B12 is useful to perform several functions in the human body like producing red blood cells. It is particularly important for women in childbearing years and the elderly, however, optimum levels of vitamin B12 over the entire lifecycle of a person are needed for overall optimum health (30).

Having low levels of this nutrient causes physical and psychological problems like nerve damage, difficulty thinking, tiredness, and fatigue. This deficiency is very common and can show up through various symptoms making it difficult to diagnose.

It is best to be able to get enough vitamin B12 through diet and most people can rectify or prevent this deficiency by doing this. In cases where this is not possible due to various reasons, one can take oral supplements or fortified foods. Vegetarians and vegans are more prone to this deficiency.

Most often, doctors can treat this deficiency. Catching this deficiency early by spotting these symptoms and getting the right treatment can make a big difference to the person.

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