The Sneaky and Harmful Effects of Vitamin B12 Deficiency

Vitamin B12 is a vital nutrient that is necessary for our bodies to function properly. It helps to maintain the health of nerve cells, produce DNA, and promote healthy red blood cells. Vitamin B12 is found in meat, fish, eggs, and dairy products. Our bodies cannot produce vitamin B12 on their own, which is why we must obtain it through our diet or supplements.

Getting enough vitamin B12 is essential for good health. Without enough vitamin B12, our bodies are at risk for a wide range of problems. Vitamin B12 deficiency can cause anemia, nerve damage, and other serious health issues. It is estimated that up to 15% of people in the United States may be deficient in vitamin B12.

Basics of vitamin B12 deficiency are simple. A vitamin B12 deficiency occurs when the body doesn't have enough vitamin B12 to properly function. The body needs vitamin B12 to help create healthy red blood cells and to maintain nerve cells. Without it, the body can't make red blood cells that are small, round, and flexible enough to move oxygen around the body. Nerve cells can also suffer damage, which can lead to tingling, numbness, and other issues.

Causes of Vitamin B12 Deficiency

There are several causes of Vitamin B12 Deficiency.

Vegan and Vegetarian Diets

Vegan and Vegetarian Diets are one of the most common causes of Vitamin B12 Deficiency. Vitamin B12 is commonly found in animal products, so those who avoid eating meat, dairy and eggs need to take supplements.

Poor Absorption

Poor Absorption is another factor that can cause Vitamin B12 Deficiency. Individuals who have digestive issues and are unable to absorb nutrients can develop Vitamin B12 Deficiency. Individuals suffering from celiac disease, Crohn's disease, and chronic inflammation in the digestive tract are at high risk.


Gastrectomy is the surgical removal of part or all of the stomach. This surgery can affect the body's ability to absorb nutrients including Vitamin B12.

Gastric Bypass

Gastric Bypass is a type of weight loss surgery that can cause Vitamin B12 Deficiency. The surgery can reduce the size of the stomach and change the way the body absorbs food, leading to nutrient deficiencies such as Vitamin B12.

Pernicious Anemia

Pernicious Anemia is a rare type of anemia that occurs when the body is unable to produce enough intrinsic factor, a protein made by the stomach that helps in the absorption of Vitamin B12.

Symptoms of Vitamin B12 Deficiency

Vitamin B12 Deficiency can cause a range of symptoms that can negatively impact an individual's quality of life if not addressed. Here are some common symptoms:

Fatigue and Weakness

  • Generalized weakness, lack of energy, and physically feeling tired even after a good night's sleep

Pale Skin

  • Pallor, paleness of the skin is a symptom of Vitamin B12 Deficiency. The skin may appear pale or yellowish

Numbness and Tingling

  • Numbness or tingling sensations in the hands, feet or other extremities are a common symptom of Vitamin B12 Deficiency.

Difficulty Balancing

  • Those with a deficiency in Vitamin B12 may struggle with balancing themselves while walking.

Depression and Confusion

  • A deficiency of Vitamin B12 can cause changes in mood, including depression and confusion. Individuals may have difficulty concentrating and focusing on tasks.

It is important to speak with a medical professional if any of these symptoms persist or occur. Blood tests can be performed to determine Vitamin B12 levels and can help to determine the cause of the deficiency. For those on a vegan or vegetarian diet, supplements are available, and for those with absorption issues, injections or dietary changes may be recommended.

Complications of Vitamin B12 Deficiency

Vitamin B12 is crucial for the proper functioning of many bodily systems. If an individual is deficient in this essential vitamin, it can lead to several serious complications:

Heart Disease

  • Vitamin B12 deficiency has been linked to an increased risk of heart disease caused by high levels of homocysteine in the blood. Elevated homocysteine levels can cause damage to blood vessels, leading to narrowing and clots, which can result in heart attacks or strokes.

Neurological Damage

  • Vitamin B12 is essential for the proper functioning of the nervous system. A deficiency can cause neurological damage, including peripheral neuropathy, which can lead to numbness, tingling, and pain in the hands and feet. Severe cases can cause difficulty walking, muscle weakness, and even paralysis.


  • Studies have found a link between Vitamin B12 deficiency and an increased risk of dementia, including Alzheimer's disease. Researchers speculate that this is due to the role of this essential nutrient in maintaining healthy brain function and the formation of neurotransmitters that facilitate communication between brain cells.

Birth Defects

  • Pregnant women who are deficient in Vitamin B12 risk having babies with birth defects, including neural tube defects and developmental delays. It is important for pregnant women to get adequate levels of B12 to ensure the proper development of their child during gestation.


  • While the link between Vitamin B12 deficiency and cancer is still not fully understood, some studies have suggested that low levels of B12 may increase the risk of certain types of cancer, including breast, prostate, lung, and bladder cancers. More research is needed to understand this relationship fully.

Diagnosis and Treatment of Vitamin B12 Deficiency

If you suspect that you have a Vitamin B12 deficiency, it is important to seek proper diagnosis and treatment. Your healthcare provider can help to determine if you have a deficiency and the best course of treatment based on your individual needs.

Blood tests

  • A blood test can determine the levels of Vitamin B12 in your blood. Your healthcare provider may also perform additional tests, such as a complete blood count (CBC), to rule out other potential causes of symptoms.

Oral supplements

  • If you have a mild to moderate deficiency, your healthcare provider may prescribe an oral B12 supplement. These supplements come in various forms, including tablets, capsules, and liquids, and are available over the counter or as a prescription. Your provider will determine the dose and duration of treatment based on your individual needs.

Intramuscular injections

  • If you have a more severe deficiency, your healthcare provider may recommend injections of Vitamin B12. Injections are typically administered into a muscle once per day or once per week, depending on the severity of the deficiency. Your provider will determine the duration of treatment based on your individual needs.

Diet changes

  • For some individuals, Vitamin B12 deficiency can be managed or prevented through dietary changes. Foods that are high in B12 include beef, liver, clams, and fish. Vegetarians and vegans may struggle to get enough B12 from their diet and should consider supplements or fortified foods, such as cereals or plant-based milk alternatives.

Treatment of Vitamin B12 deficiency is crucial for preventing long-term complications and improving overall health. Work closely with your healthcare provider to determine the best course of action based on your individual needs.

Prevention of Vitamin B12 Deficiency

Vitamin B12 plays a crucial role in maintaining overall health and well-being. While it's important to seek proper diagnosis and treatment if you have a deficiency, prevention is key. Here are a few ways you can help ensure you're getting enough Vitamin B12:

Balanced Diet

  • Eating a balanced diet that includes foods rich in Vitamin B12 is the best way to prevent a deficiency. Foods that are particularly high in B12 include clams, liver, beef, and fish. If you're a vegetarian or vegan, consider incorporating fortified foods, such as cereals or plant-based milk alternatives, into your diet.
  • In addition to Vitamin B12, other vitamins and nutrients are important for overall health. Eating a varied diet that includes fruits, vegetables, whole grains, and lean proteins can help ensure you're getting all the nutrients you need.


  • If you're at risk for a Vitamin B12 deficiency, you may consider taking a supplement. Supplements are available in various forms, including tablets, capsules, and liquids. Be sure to talk to your healthcare provider before starting any supplements, as excessive amounts of Vitamin B12 can be harmful.
  • It's important to note that while supplements can be beneficial, they should not be relied on as a replacement for a balanced diet.

Regular Health Checkups

  • Regular health checkups can help ensure you're staying on top of your overall health, including your Vitamin B12 levels. Your healthcare provider can perform blood tests to check your B12 levels and discuss any concerns or potential risks with you.
  • If you're experiencing any symptoms of a deficiency, such as fatigue or numbness, be sure to bring them up with your healthcare provider at your next checkup.

By following a balanced diet, considering supplements if necessary, and scheduling regular health checkups, you can help prevent Vitamin B12 deficiency and maintain optimal health.


Vitamin B12 is an essential nutrient required for proper functioning of the nerve cells and red blood cells in the body. It's important to consume enough Vitamin B12, as a deficiency can lead to serious health complications. Let's recap some of the most important points:

The Importance of Vitamin B12

  • Vitamin B12 is required for proper functioning of nerve cells and red blood cells.
  • A deficiency can lead to fatigue, weakness, and other serious health complications.

Awareness of Deficiency Symptoms

  • It's important to be aware of the signs and symptoms of a Vitamin B12 deficiency.
  • If you experience ongoing fatigue, weakness, pale skin, numbness, or difficulty balancing, talk to your healthcare provider about checking your B12 levels.

Seeking Professional Help

  • If you are diagnosed with a Vitamin B12 deficiency, it's important to seek professional help.
  • Your healthcare provider can determine the underlying cause of your deficiency and recommend specific treatment options, which may include supplements or dietary changes.
William H. McDaniel, MD

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School.

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