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

The human body does not create vitamin B-12, so people must get this nutrient from their diet. It is crucial for making DNA and red blood cells, and it helps support the nervous system.

Vitamin B-12 plays a vital role in the production of blood cells.

Many of the symptoms of vitamin B-12 deficiency arise because it causes a lack of healthy blood cells. The body needs plenty of these cells to get oxygen around the body and keep the organs in good health.

A vitamin B-12 deficiency can lead to both physical and psychological problems. In this article, we explore 11 symptoms of vitamin B-12 deficiency and explain why they occur.

What to know about vitamin B-12 deficiency

vitamin b12 deficiency symptoms
Vitamin B-12 deficiency can cause symptoms that impact a person’s mental and physical health.

Vitamin B-12 deficiency may affect between 1.5 and 15.0 percent of people.

This deficiency can cause a wide range of symptoms that affect a person’s mental and physical health.

The body cannot store vitamin B-12, so it is important to consume foods that contain it on a regular basis. Adults need around 2.4 micrograms (mcg) of vitamin B-12 each day.

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

  • red meat
  • poultry
  • eggs
  • dairy
  • fish

If a person does not eat animal products, they will need to add vegetarian and vegan sources of vitamin B-12 to their diet. These include fortified cereals, plant milks, bread, and nutritional yeast.

As vitamin B-12 deficiency shares many symptoms with other nutritional deficiencies and health conditions, it is possible that people may neither notice it nor get a diagnosis.

Being aware of all of the signs can help people identify the deficiency and seek treatment.

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

1. Tingling hands or feet

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

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

People who are vitamin B-12 deficient may not produce enough myelin to coat their nerves. Without this coating, nerves can become damaged.

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

2. Trouble walking

Over time, peripheral nerve damage resulting from vitamin B-12 deficiency can lead to movement problems.

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

3. Pale skin

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

Jaundice develops when a person’s body is not able to produce enough red blood cells. Red blood cells circulating under the skin provide it with its normal color. Without enough of these cells, the skin may look pale.

Vitamin B-12 plays a role in the production of red blood cells. A vitamin B-12 deficiency can cause a lack of red blood cells, or megaloblastic anemia, which has an association with jaundice.

This type of anemia can also weaken the red blood cells, which the body then breaks down more quickly. When the liver breaks down red blood cells, it releases bilirubin. Bilirubin is a brownish substance that gives the skin the yellowish tone that is characteristic of jaundice.

4. Fatigue

Megaloblastic anemia due to vitamin B-12 deficiency may lead to a person feeling fatigued.

Without enough red blood cells to carry oxygen around their body, a person can feel extremely tired.

5. Fast heart rate

vitamin b12 deficiency symptoms fatigue
A fast heart rate and shortness of breath may be symptoms of vitamin B-12 deficiency.

A fast heart rate may be a symptom of vitamin B-12 deficiency.

The heart may start to beat faster to make up for the reduced number of red blood cells in the body.

Anemia puts pressure on the heart to push a higher volume of blood around the body and to do it more quickly. This response is the body’s way of trying to ensure that enough oxygen circulates through all of the body’s systems and reaches all the organs.

6. Shortness of breath

Anemia that results from vitamin B-12 deficiency may cause a person to feel a little short of breath. It is possible to link this to a lack of red blood cells and a fast heartbeat.

Anyone who is experiencing real difficulty breathing should see a doctor straight away.

7. Mouth pain

Vitamin B-12 affects oral health. As a result, being deficient in vitamin B-12 may cause the following mouth problems:

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

These symptoms occur because vitamin B-12 deficiency causes a reduction in red blood cell production, which results in less oxygen reaching the tongue.

8. Problems thinking or reasoning

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

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

The reduced amount of oxygen reaching the brain might be to blame for the thinking and reasoning problems.

9. Irritability

Being deficient in vitamin B-12 can affect a person’s mood, potentially causing irritability or depression.

There is a need for more research into the link between vitamin B-12 and mental health. One theory is that vitamin B-12 helps break down a brain chemical called homocysteine. Having too much homocysteine in the brain may cause mental health problems.

10. Nausea, vomiting, and diarrhea

Vitamin B-12 deficiency can affect the digestive tract.

A lack of red blood cells means that not enough oxygen reaches the gut. Insufficient oxygen here may lead to a person both feeling and being sick. It may also cause diarrhea.

11. Decreased appetite and weight loss

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


vitamin b12 deficiency symptoms vegan diet
Eating a vegan diet increases the risk of vitamin B-12 deficiency.

Even if a person gets enough vitamin B-12 in their diet, some underlying health conditions can affect the absorption of vitamin B-12 in the gut.

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 vitamin B-12 from dietary sources. For those who cannot, a doctor may prescribe or recommend B-12 supplements. People can also get B-12 supplements from drug stores or choose between brands online.

Most multivitamins contain vitamin B-12. People can take B-12 supplements in the form of oral tablets, sublingual tablets that dissolve under the tongue, or injections. A doctor can provide advice on the correct dosage of this vitamin.

People who have trouble absorbing vitamin B-12 may need shots of the vitamin to treat their deficiency.

A doctor can advise people on the best way to prevent vitamin B-12 deficiency, depending on their dietary choices and health.


The body needs vitamin B-12 for a range of bodily functions, which include making red blood cells. Being deficient in vitamin B-12 causes physical and psychological symptoms, including nerve problems, fatigue, and difficulty thinking.

Most vitamin B-12 deficiency symptoms occur due to a lack of red blood cells, which means that the body does not get enough oxygen. The body’s oxygen supply is crucial for many aspects of health.

As with other nutrients, the best way for most people to get vitamin B-12 is in the diet. If a person cannot get enough from their usual diet, fortified foods and other dietary supplements may help.

In most cases, doctors can treat vitamin B-12 deficiency. However, people with long-term deficiency may have long-lasting effects, such as nerve damage.

Spotting the signs of vitamin B-12 deficiency early on and getting the right treatment can improve a person’s outlook.