You are currently viewing What are the symptoms of vitamin B-12 deficiency?
"asian businessman sitting in office, looking tired. click for more: abusiness peopleai"

What are the symptoms of vitamin B-12 deficiency?

Vitamin B-12 is an essential nutrient which ensures that the body functions properly. Symptoms of deficiency in vitamin B-12 include fatigue, low mood and nerve problems..

The human body is not making vitamin B-12, so people have to get this nutrient from their diet. Making DNA and red blood cells is important and it helps support the nervous system.

Vitamin B-12 plays a crucial role in building blood cell development.

Many of the vitamin B-12 deficiency symptoms occur as it causes a shortage of healthy cells in the blood. The body needs a lot of these cells to get oxygen throughout the body to keep the organs in good condition.

A deficiency of vitamin B-12 can cause physical as well as psychological problems. Within this article we describe 11 vitamin B-12 deficiency symptoms and explain why they occur.

What to know about vitamin B-12 deficiency

A tired man sitting in office
Vitamin B-12 deficiency can cause symptoms that impact a person’s mental and physical health.

Deficiency of vitamin B-12 can affect 1.5 to 15.0 percent of people.

This deficiency can cause a vast array of symptoms that affect the mental and physical health of a person.

It is essential that foods containing vitamin B-12 are consumed regularly. Every day adults require around 2.4 micrograms ( mcg) of vitamin B-12.

Vitamin B-12 is a water-soluble vitamin present in animal – based foods, such as:

  • red meat
  • poultry
  • eggs
  • dairy
  • fish

If a person doesn’t eat animal products, they need to add vegetarian and vegan vitamin B-12 sources to their diet. Which include fortified cereals, plant milk, bread, and nutritional yeast.

Because the deficiency of vitamin B-12 shares many symptoms with other nutritional deficiencies and health conditions, people may not notice it or be diagnosed.

Being conscious of all the symptoms will help recognize the disorder and search for treatment.

Below we look at the symptoms and their causes of vitamin B-12 deficiency.

Tingling hands or feet

Deficiency of vitamin B-12 in the hands or feet can cause “pins and needles.” This symptom occurs because the vitamin plays a crucial role in the nervous system, and its absence can cause problems with nerve conduction or nervous damage to people.

Vitamin B-12 helps to produce a substance, called myelin, in the nervous system. Myelin is a protective coating that shields the nerves and helps them transmit sensations.

People who are deficient in vitamin B-12 may not produce sufficient myelin to coat their nerves. Without this coating it can damage the nerves.

Problems in the hands and feet, which are called peripheral nerves, are more common. Peripheral nerve damage may lead to tingling in these parts of the body.

Trouble walking

Over time, peripheral nerve damage caused by a lack of vitamin B-12 can lead to issues with movement.

Numbness in the feet and limbs may make it hard for a person to walk without support. They can also experience fatigue in the muscles and diminished reflexes.

Pale skin

Pale or yellow skin, known as jaundice, may be a deficiency of vitamin B-12.

Jaundice occurs when there is not enough red blood cells in a person’s body. Red blood cells which circulate under the skin give it its normal color. The skin can look pale without enough of those cells.

Vitamin B-12 plays a part in red blood cell development. A deficiency in vitamin B-12 may cause a lack of red blood cells, or megaloblastic anemia, which has a jaundice association.

Such form of anemia can also damage the red blood cells which the body breaks down faster afterwards. As red blood cells break down the liver it produces bilirubin. Bilirubin is a brownish substance that gives the skin the yellowish tone that is characteristic of jaundice.


Megaloblastic anemia due to deficiency of vitamin B-12 can cause a person to feel fatigued.

An individual may feel extremely tired without enough red blood cells to bring oxygen throughout his or her body.

Fast heart rate

A fast heart rate and shortness of breath may be symptoms of vitamin B-12 deficiency.

A rapid heart rate can be a symptom of a deficiency of vitamin B-12.

The heart may begin beating more quickly to compensate for the reduced number of red blood cells in the body.

Anemia puts pressure on the heart to push a higher blood volume around the body, and to do it faster. This response is the way in which the body tries to ensure that enough oxygen circulates through all the processes of the body and enters all organs.

Shortness of breath

Anemia that results from a deficiency of vitamin B-12 can cause a person to feel a bit short of breath. This can be linked to a lack of red blood cells and a rapid heart beat.

Anyone who has real breathing difficulties should see a doctor immediately.

Mouth pain

The effect of vitamin B-12 on the oral health. Because of this, vitamin B-12 deficiency can cause the following mouth problems:

  • glossitis, which causes a swollen, smooth, red tongue
  • mouth ulcers
  • a burning sensation in the mouth

Such symptoms occur because the deficiency of vitamin B-12 leads to a reduction in the production of red blood cells which results in less oxygen entering the tongue.

Problems thinking or reasoning

Vitamin B-12 deficiency may cause problems with thinking, which doctors refer to as cognitive impairment. Those issues include thinking or reasoning difficulties and loss of memory.

One study even linked low levels of vitamin B-12 to a higher risk of Alzheimer’s disease, vascular dementia, and Parkinson’s disease.

The reduced amount of oxygen that reaches the brain could be to blame for the problems of thinking and reasoning.


Deficient in vitamin B-12 may affect a person ‘s mood, possibly leading to irritability or depression.

More research is needed on the connection between vitamin B-12 and mental health. One theory is that vitamin B-12 contributes in breaking down a chemical called homocysteine in the brain. Too much homocysteine can cause mental health problems in the brain.

Nausea, vomiting, and diarrhea

Deficiency of vitamin B-12 can affect the digestive tract.

A lack of red blood cells means the gut is not receiving enough oxygen. Insufficient oxygen here can cause a person to feel as well as to be sick. This can cause diarrhea, as well.

Decreased appetite and weight loss

People with a vitamin B-12 deficiency may lose their appetite as a result of digestive problems, such as nausea. A decreased appetite can lead to weight loss in the long term.


Vegan diet
Eating a vegan diet increases the risk of vitamin B-12 deficiency.

Even if a person’s diet contains enough vitamin B-12, some underlying health conditions can affect the absorption of vitamin B-12 in the intestine.

These conditions include:

The following factors make a person more likely to have a vitamin B-12 deficiency:

  • being older, because a person becomes less able to absorb B-12 as they age
  • eating a vegetarian or vegan diet
  • taking anti-acid medication for an extended period
  • weight loss surgery or other stomach surgery, which can affect how the digestive system absorbs vitamin B-12

Treatment and prevention

Most people can get enough of the dietary vitamin B-12. A doctor can prescribe or recommend B-12 supplements for those unable to do so. B-12 supplements can also be purchased from drug stores.

The vitamin B-12 is present in most multivitamins. People can take B-12 supplements in the form of oral tablets, sublingual tablets, or injections that dissolve under the tongue. A doctor may give advice regarding the correct dosage of this vitamin.

People with vitamin B-12 absorption difficulties may need vitamin shots to treat their deficiency.

A doctor will advise patients about how best to avoid deficiencies in vitamin B-12, based on their food preferences and health.


The body needs vitamin B-12 for a range of body functions that include the production of red blood cells. Deficient in vitamin B-12 causes physical and psychological symptoms including problems with the nerves, tiredness, and difficulty thinking.

Most of the symptoms of vitamin B-12 deficiency are due to a lack of red blood cells , which means the body doesn’t get enough oxygen. Supplying oxygen to the body is crucial for many health aspects.

As with other nutrients, the best way to get vitamin B-12 is through diet for most people. If a person is unable to get enough of their usual diet, strengthened foods and other dietary supplements may help.

In most cases, the vitamin B-12 deficiency may be treated by doctors. However, people with a long-term deficiency may have long-term effects, such as damage to the nerves.

Prompt identification of the symptoms of vitamin B-12 deficiency and having the right treatment will boost a person’s perspective.

Chukwuebuka Martins

Chukwuebuka Martins is a writer, researcher, and health enthusiast who specializes in human physiology. He takes great pleasure in penning informative articles on many aspects of physical wellness, which he then thoroughly enjoys sharing to the general public.