Vitamin B12 Deficiency Symptoms, from Fatigue to Mouth Sores

Vitamin B12 plays crucial roles in maintaining the health of your blood cells, digestive system, brain, and nervous system.

vitamin b12 deficiency symptoms

Fatigue isn't the only symptom of low B12.

© Tirachard Kumtanom |

Vitamin B12 deficiency is best known as a cause of fatigue, but this vitamin is important for much more than keeping energy levels up. Vitamin B12 deficiency symptoms include depression, sore mouth, memory loss, and dizziness.

The vitamin B12 plays crucial roles in maintaining the health of your blood cells, digestive system, brain, and nervous system. While fatigue due to anemia is sometimes a symptom, recent research shows that many people have vitamin B12 deficiency without anemia or significant fatigue. Instead, they may have vitamin B12 deficiency symptoms that are more related to impairments in the nervous system.

Low B12 Symptoms

In the nervous system, vitamin B12 is necessary for the formation of myelin, a whitish insulating sheath around nerve fibers that increases the speed at which impulses are conducted. It is also needed for the production of some neurotransmitters. Other common symptoms are caused by loss of red blood cells, called anemia.

The most common symptoms of low vitamin B12 include:

Risk Factors for B12 Deficiency

Risk factors for vitamin B12 deficiency include:

  • Being over age 50 because you may produce less stomach acid and have trouble absorbing B12 from your diet
  • Having a disease called pernicious anemia, which decreases stomach acid and B12 absorption
  • Being a vegetarian, because B12 is not found in plant foods
  • Having a digestive system disease or surgery that interferes with your abiotic to absorb B12

How to Treat Vitamin B12 Deficiency Symptoms

Treatment for vitamin B12 deficiency usually starts with B12 injections. Some patients need regular injections for life, depending on the cause of the deficiency. After vitamin B12 shots have returned the body’s levels to normal, it’s possible to switch to oral vitamin B12 supplements.

Research shows that people who are not B12 deficient do not benefit from supplements. If you have symptoms of B12 deficiency talk to your doctor. The best way to diagnose B12 deficiency and the cause is with blood testing.


Does following a vegan diet leave you with vitamin B12 deficiency symptoms? It’s something to consider, experts say. After all, fish, meat, poultry, eggs, and dairy products—all foods not included in a vegan diet—are classic sources of vitamin B12. So it’s a good idea to have your B12 levels checked when you have your annual blood work done. Very low levels may suggest you need monthly or bi-weekly B12 injections to restore and maintain healthy levels.

Vitamin B12 is essential for healthy functioning of your brain, nervous system, and metabolism. Vitamin B12 deficiency symptoms may include:

    • Fatigue and muscle weakness and even such alarming symptoms as heart palpitations and shortness of breath
    • Nerve problems such as numbness and tingling, especially in your hands and feet. These symptoms may even affect your ability to walk properly
    • Changes in the way your tongue looks. It may become smoother but swollen
    • Changes in your skin’s appearance; it may become pale or jaundiced
    • Emotions and your thinking. People with low B12 levels often complain of memory problems and depressive symptoms. If left untreated, B12 deficiency can lead to serious brain issues and other neurological problems.

Without a blood test to confirm the problem, you may not even know that you have vitamin B12 deficiency, according to the March 2017 issue of Women’s Nutrition Connection. A doctor may recognize the possibility of B12 deficiency based on a physical exam and a review of your symptoms, and a simple blood test can reveal your actual B12 levels.



This post originally appeared in 2014 and has been updated regularly.

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UHN Staff

University Health News is produced by the award-winning editors and authors of Belvoir Media Group’s Health & Wellness Division. Headquartered in Norwalk, Conn., with editorial offices in Florida, Cleveland, Pittsburgh, … Read More

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