Vitamin B12 Deficiency Illustration

Vitamin B12 Deficiency: Symptoms and How to Avoid (2024)

by | Aug 21, 2023

Vitamin B12, an essential nutrient, plays a pivotal role in numerous bodily functions, from DNA synthesis to red blood cell formation.

However, when its levels fall short in the body, it can lead to a range of health problems, both subtle and profound.

Despite the widespread availability of B12 in various foods and supplements, deficiencies persist, and understanding its implications, causes, and prevention is critical for public health.

What is Vitamin B12?

Vitamin B12, also known as cobalamin, is a water-soluble vitamin essential for various critical functions in the human body. Here’s a brief overview:

Chemical Structure

Cobalamin’s name hints at its unique structure, as it contains a cobalt atom. This makes vitamin B12 the only vitamin that contains a metal ion.

Functions in the Body

  • DNA Synthesis: B12 plays a role in DNA synthesis, which is crucial for the formation of new cells.
  • Red Blood Cell Formation: It is vital for the maturation of red blood cells in the bone marrow.
  • Neurological Function: B12 is essential for the maintenance of the nervous system, including the formation of the myelin sheath, which surrounds and protects nerve fibers.
  • Homocysteine Metabolism: Along with folic acid and vitamin B6, B12 helps in the conversion of homocysteine to methionine, thereby reducing the risk of cardiovascular diseases.


  • Animal-Based Foods: Naturally occurring B12 is found predominantly in animal products, including fish, meat, poultry, eggs, milk, and dairy products.
  • Fortified Foods: For vegetarians or vegans, certain plant-based foods are fortified with B12, such as plant-based milk alternatives and cereals.
  • Supplements: B12 supplements are available in various forms, including oral tablets, sublingual lozenges, and injections.
  • Absorption: Vitamin B12 absorption is a complex process that requires a substance called intrinsic factor (produced by cells in the stomach). Any disruption in this process, such as in pernicious anemia, can lead to B12 deficiency.

In essence, vitamin B12 is indispensable for maintaining overall health, especially neurological and hematological well-being.

Proper intake and absorption are crucial, making awareness of its sources and functions vital.

Vitamin B12 Deficiency Food Vector Illustration

Vitamin B12 Benefits

Vitamin B12, or cobalamin, is a critical nutrient for human health, and its adequate intake offers a range of benefits:

  • Supports Red Blood Cell Formation: B12 is vital for the production and maturation of red blood cells, helping prevent a specific type of anemia called megaloblastic anemia, which can lead to fatigue and weakness.
  • Maintains Nervous System Health: B12 is instrumental in the formation of the protective covering of nerves, known as the myelin sheath. This helps prevent nerve damage and maintain proper nerve function, which is crucial for transmitting signals throughout the body.
  • Aids in DNA Production: B12 plays a significant role in DNA synthesis, which is fundamental for cell division and repair.
  • Promotes Brain Health: Adequate levels of B12 can support cognitive functions, potentially reducing the risk of age-associated neurodegenerative conditions and mood disorders like depression.
  • Homocysteine Regulation: Along with other B vitamins, B12 helps regulate homocysteine levels in the blood. Elevated homocysteine has been linked to increased risks of heart disease.
  • Supports Energy Production: B12 is involved in converting the food we eat into glucose, which is used by our body for energy. Consequently, its deficiency may lead to fatigue.
  • Assists with Protein Metabolism: B12 assists in the transformation of proteins in the body, supporting muscle repair and growth.
  • Supports Healthy Skin, Hair, and Eyes: By playing a role in cell production, B12 can contribute to the health of skin, hair, and eyes.
  • Promotes Fetal Development: During pregnancy, B12 is crucial for the development of the nervous system of the fetus, making adequate intake essential for expecting mothers.
  • Prevents Major Birth Defects: Adequate B12 levels can help prevent major birth defects related to the baby’s spine and central nervous system.

It’s evident from these benefits that maintaining proper B12 levels is crucial for a multitude of physiological processes and overall well-being.

What is a Vitamin B12 Deficiency?

Vitamin B12 deficiency arises when the body lacks enough of this essential nutrient to function optimally. B12 is crucial for processes like red blood cell formation and DNA synthesis, and its deficiency can lead to anemia and neurological complications.

Often stemming from inadequate dietary intake, malabsorption conditions, or the lack of intrinsic factor necessary for its absorption, this deficiency can manifest as fatigue, weakness, cognitive disturbances, and more.

Certain groups, such as vegans and the elderly, are especially prone, underscoring the importance of regular monitoring and appropriate dietary or supplemental intake.

Causes of Vitamin B12 Deficiency

Vitamin B12 deficiency can arise from a variety of causes that span issues related to intake, absorption, and underlying medical conditions.

Here are the primary causes of B12 deficiency:

  • Dietary Restrictions: Individuals who follow a strict vegetarian or vegan diet and don’t consume animal products might not get enough vitamin B12.
  • Pernicious Anemia: An autoimmune condition in which the body destroys intrinsic factor, a protein made in the stomach that’s necessary for B12 absorption.
  • Atrophic Gastritis: Inflammation and thinning of the stomach lining can reduce the stomach’s ability to produce intrinsic factor.
  • Surgical Removal of Parts of the Stomach or Small Intestine: Procedures like gastric bypass surgery can affect B12 absorption.
  • Digestive Disorders: Conditions such as celiac disease, Crohn’s disease, atrophic gastritis, and bacterial growth in the small intestine can interfere with B12 absorption.
  • Chronic Alcoholism: Excessive alcohol consumption can lead to issues with B12 absorption.
  • Long-term Use of Acid-reducing Drugs: Medications like proton pump inhibitors (PPIs) and H2 blockers reduce stomach acid, which is needed to release B12 from food for absorption.
  • Fish Tapeworm: Infestation with this parasite can lead to B12 deficiency as the tapeworm consumes B12 in the intestines.
  • Age: The ability to absorb vitamin B12 might decrease with age, increasing the risk of deficiency in older adults.
  • Chronic Use of Certain Medications: Beyond acid-reducing drugs, some anticonvulsants, antacids, and medications for type 2 diabetes (like metformin) may decrease B12 absorption.
  • Immune System Disorders: Conditions like Graves’ disease or lupus can affect vitamin B12 absorption.
  • Lack of Stomach Acid: The elderly and individuals on long-term antacid treatments may have reduced stomach acid, which is essential for releasing B12 from food proteins.

It’s worth noting that even if one’s dietary intake of vitamin B12 is adequate, issues with absorption can still lead to a deficiency.

If someone suspects they have a B12 deficiency or are at risk of developing one, it’s essential to consult with a healthcare professional for evaluation and guidance.

Symptoms of Vitamin B12 Deficiency

Vitamin B12 deficiency can manifest in various ways, affecting multiple systems in the body. Here are some of the common symptoms:

  • Fatigue and Weakness: Insufficient B12 can lead to decreased red blood cell production, resulting in anemia and associated fatigue.
  • Anemia: Specifically, megaloblastic anemia, where red blood cells produced in the bone marrow become enlarged and immature, making it hard for them to carry oxygen.
  • Neuropathy: This includes tingling and numbness in the hands and feet, unsteady movements, and muscle weakness. The nervous system can be impacted due to the demyelination of nerve cells.
  • Mood Changes and Depression: B12 plays a role in synthesizing and metabolizing neurotransmitters related to mood regulation.
  • Vision Problems: Damage to the optic nerve can lead to vision disturbances.
  • Memory Loss and Dementia: In severe cases, prolonged B12 deficiency can lead to cognitive disturbances, which might be mistaken for age-related dementia.
  • High Levels of Homocysteine: Elevated homocysteine levels are associated with an increased risk of heart diseases, strokes, and other cardiovascular conditions.
  • Shortness of Breath and Dizziness: Related to decreased oxygen transport due to anemia.
  • Pale or Jaundiced Skin: B12 deficiency can cause the body to produce large, fragile red blood cells that break down easily, leading to an excess of bilirubin, giving the skin and eyes a pale yellow hue.
  • Heart Palpitations: Resulting from the decreased oxygen-carrying capacity of the blood.
  • Difficulty in Walking: This can arise due to nerve damage and muscle weakness.
  • Swollen and Inflamed Tongue: Also known as glossitis, which can change the way a person talks and eats.
  • Difficulty Concentrating and Reasoning: Cognitive functions can be impacted.

If someone suspects a B12 deficiency, it’s crucial to consult a healthcare professional for an accurate diagnosis, as many of these symptoms can overlap with other health conditions.

Dangers of Vitamin B12 Deficiency

Vitamin B12 deficiency, if left untreated, can lead to a range of serious health complications. Here are some of the potential dangers associated with prolonged B12 deficiency:

  • Neurological Damage: Persistent deficiency can lead to irreversible nerve damage. This can manifest as numbness, tingling in the extremities, difficulty walking, and even memory loss or cognitive decline.
  • Megaloblastic Anemia: A reduced level of B12 interferes with the ability of bone marrow to produce healthy red blood cells. This can result in fatigue, weakness, and shortness of breath due to the decreased oxygen-carrying capacity of the blood.
  • Heart Disease: Elevated homocysteine levels, which can occur due to B12 deficiency, are associated with a higher risk of cardiovascular diseases, including heart attacks and strokes.
  • Mental Health Issues: Besides cognitive decline, B12 deficiency has been linked to mood disturbances like depression, anxiety, and changes in behavior.
  • Vision Loss: The deficiency can damage the optic nerve leading to vision problems or, in severe cases, permanent vision loss.
  • Bone Health: Some studies suggest that a B12 deficiency can lead to decreased bone mineral density, increasing the risk of osteoporosis and fractures.
  • Infertility: B12 deficiency can impact fertility and may lead to miscarriage.
  • Neural Tube Defects: Inadequate B12 during pregnancy can increase the risk of neural tube defects in the developing fetus, leading to conditions like spina bifida.
  • Poor Immune Function: B12 is vital for the proper function of the immune system. Deficiency can reduce the body’s ability to ward off infections.
  • Gastric Cancer: Chronic atrophic gastritis, often associated with B12 deficiency, increases the risk of stomach cancer.

Given these potential dangers, it’s essential for individuals, especially those at higher risk (such as the elderly, vegetarians, vegans, and those with certain medical conditions), to monitor their B12 levels and ensure they receive adequate amounts through diet or supplements.

If any symptoms of deficiency appear, immediate consultation with a healthcare professional is crucial.

Treatment of Vitamin B12 Deficiency

Treatment for vitamin B12 deficiency is designed to replenish B12 levels in the body. The specific approach will depend on the cause of the deficiency and its severity.

Here are the common treatments for B12 deficiency:

  • B12 Injections: For individuals with severe deficiencies, especially those who cannot absorb B12 through their digestive system due to conditions like pernicious anemia, regular B12 injections are typically recommended. The frequency of these injections will depend on the severity of the deficiency but might start with daily or weekly injections and then decrease in frequency as B12 levels are restored.
  • Oral B12 Supplements: Over-the-counter vitamin B12 tablets are available and can be effective for individuals with milder deficiencies or those who have difficulty obtaining enough B12 from food.
  • Sublingual B12: This is B12 that dissolves under the tongue, and it’s believed to be absorbed directly into the bloodstream, bypassing the digestive system.
  • Dietary Changes: For those with a deficiency due to dietary limitations, increasing the intake of B12-rich foods can help. This might include incorporating more fish, poultry, meat, eggs, and dairy. For vegans and strict vegetarians, consuming B12-fortified foods like plant-based milks and cereals can be beneficial.
  • Nasal Gel or Spray: These are alternative methods to increase B12 levels for individuals who might not want injections or tablets.
  • Managing Underlying Conditions: In cases where B12 deficiency is caused by an underlying health condition, it’s vital to treat that condition. This might involve addressing stomach or intestinal disorders, discontinuing or changing medications that interfere with B12 absorption, or managing conditions like atrophic gastritis.
  • Regular Monitoring: After starting treatment, it’s essential to monitor B12 levels through blood tests to ensure they are rising to appropriate levels and to adjust the treatment regimen if necessary.

It’s worth emphasizing that self-diagnosis and treatment of a B12 deficiency can be risky since the symptoms can be similar to those of other conditions.

It’s essential to consult with a healthcare professional to get an accurate diagnosis and appropriate treatment recommendations.

Food High in Vitamin B12

Vitamin B12 is primarily found in animal products, making it essential for vegetarians and vegans to be especially conscious of their intake.

Here are some foods that are high in vitamin B12:

  • Shellfish: Particularly clams and oysters. These are among the richest sources of B12.
  • Liver: Especially beef liver, which is incredibly high in vitamin B12.
  • Fatty Fish: Examples include mackerel, sardines, tuna, salmon, and trout.
  • Red Meat: Beef and lamb are notable sources.
  • Poultry: Chicken and turkey, though they contain less B12 compared to red meat.
  • Eggs: Particularly the yolk.
  • Dairy Products: This includes milk, cheese, and yogurt. Even low-fat dairy products are good sources of B12.
  • Fortified Foods: Many plant-based foods, like non-dairy milks (soy, almond, rice milk), breakfast cereals, and meat substitutes, are fortified with vitamin B12, making them viable sources for vegetarians and vegans.
  • Fortified Non-Dairy Milks: As the popularity of vegan diets has increased, many plant-based milk alternatives have been fortified with B12.
  • Crab and Lobster: While not as high as clams, these seafood options still offer good amounts of B12.
  • Fortified Plant-Based Meat Substitutes: Many products designed to mimic meat’s taste and texture are now fortified with essential vitamins, including B12.
  • Nutritional Yeast: Often used in vegan cooking, some nutritional yeast products are fortified with B12.
  • Insects: In some cultures, insects are a dietary staple and can also be a source of B12.

Note: While the B12 content in these foods can vary depending on factors like preparation methods and where the food is sourced, they generally offer significant amounts of this crucial vitamin.

People on strict vegetarian or vegan diets, or those with certain health conditions that hinder B12 absorption, should consider supplements or fortified foods to ensure adequate intake.

Always consult a healthcare professional before making significant changes to one’s diet or taking supplements.

FAQs About Vitamin B12

What is Anemia?

Anemia is a medical condition characterized by a reduced number of red blood cells or a decreased amount of hemoglobin in the blood.

This reduction compromises the blood’s ability to transport oxygen to the body’s tissues, leading to symptoms like fatigue, pallor, shortness of breath, and palpitations.

Several factors can cause anemia, including nutrient deficiencies (like iron, vitamin B12, and folic acid), chronic diseases, bone marrow disorders, and more.

How is Vitamin B12 Deficiency Diagnosed?

Vitamin B12 deficiency is diagnosed through blood tests. A healthcare professional may measure the actual vitamin B12 level in the blood or look at the level of methylmalonic acid (MMA), a substance that increases in the blood when vitamin B12 levels are low.

Additionally, a complete blood count (CBC) can be helpful.

In B12 deficiency anemia, the red blood cells may be larger than normal, a condition referred to as macrocytosis or megaloblastic anemia.

What Happens When Vitamin B12 Level is Low?

When vitamin B12 levels are low, it can disrupt the formation of red blood cells, leading to megaloblastic anemia. This type of anemia is characterized by larger-than-normal and immature red blood cells, reducing their oxygen-carrying capacity.

Additionally, B12 plays a crucial role in nerve function, so its deficiency can lead to neurological symptoms such as numbness, tingling, weakness, and balance issues.

Low B12 can also result in mood disturbances, cognitive difficulties, fatigue, and, over time, irreversible nerve damage if not addressed.

What is the Main Cause of Vitamin B12 Deficiency?

The main causes of vitamin B12 deficiency include inadequate dietary intake (common in vegetarians or vegans), malabsorption (often due to conditions like pernicious anemia, atrophic gastritis, or surgeries that remove parts of the stomach or small intestine), and certain medications (like proton pump inhibitors and metformin) that reduce B12 absorption.

Age can also be a factor, as older adults may produce less stomach acid, which is needed to absorb B12 effectively.

What is the Fastest Way to Fix Vitamin B12 Deficiency?

The fastest way to address a vitamin B12 deficiency typically involves receiving vitamin B12 injections. These injections bypass the digestive system, providing an immediate boost to B12 levels in the body.

They’re especially beneficial for individuals with malabsorption issues.

Depending on the severity of the deficiency, injections might be administered daily or weekly initially, then monthly once levels stabilize. For those without absorption problems, high-dose oral supplements can also be effective.

Is Folic Acid and Vitamin B12 the Same?

No, folic acid and vitamin B12 are not the same. They are both B vitamins and play crucial roles in the body’s metabolic processes, but they have distinct functions. Folic acid (also known as vitamin B9) is vital for DNA synthesis and cell division.

Vitamin B12 is essential for nerve function and the formation of red blood cells. While they work together in some cellular processes, a deficiency in one doesn’t mean there’s a deficiency in the other.

However, it’s worth noting that high levels of folic acid can mask a vitamin B12 deficiency, which can delay its diagnosis and treatment.

How Long Does it Take to Recover from Vitamin B12 Deficiency?

The recovery time from vitamin B12 deficiency varies depending on its severity and the treatment method. With B12 injections, some individuals might experience symptom relief within a few days, though it can take several weeks for the deficiency to be fully corrected.

When treated with oral supplements, recovery might take a bit longer.

It’s important to note that while some symptoms, like fatigue, may improve quickly, others, especially neurological symptoms, might take longer to resolve and, in some cases, may not fully reverse.

Does Vitamin B12 Deficiency Cause Weight Gain?

There isn’t direct evidence that vitamin B12 deficiency causes weight gain. However, a deficiency can lead to fatigue and weakness, reducing a person’s physical activity and potentially influencing weight.

Some people might mistakenly believe that B12 injections or supplements can boost energy and metabolism, leading to weight loss.

While B12 can increase energy levels if someone was deficient, it doesn’t directly cause significant weight loss or gain in individuals with normal B12 levels.

Can Vitamin B12 Deficiency Cause Headaches?

Yes, vitamin B12 deficiency can cause headaches. The deficiency may lead to a decreased ability of the blood to carry oxygen efficiently, causing symptoms like dizziness and headaches.

Additionally, B12 is vital for nerve function, and its deficiency might result in neurological symptoms, including headaches, numbness, and tingling.

Is Vitamin B12 Deficiency Serious?

Yes, vitamin B12 deficiency can be serious if left untreated. Initially, symptoms might be subtle and include fatigue, weakness, and a tingling sensation in the hands and feet.

Over time, the deficiency can lead to more severe health problems, such as anemia, nerve damage, heart disorders, and cognitive impairments.

In extreme cases, prolonged B12 deficiency can cause irreversible nerve damage and neurodegenerative disorders. Early diagnosis and prompt treatment are crucial to prevent these complications.

Final Thoughts

Vitamin B12 deficiency, though preventable, remains a significant health concern. It can manifest through a variety of symptoms that can impact quality of life and long-term health.

Early detection, understanding the risk factors, and ensuring adequate dietary or supplementary intake are essential in preventing its detrimental effects.

Awareness and education are the first steps toward mitigating the risks associated with this deficiency.

John Landry, BS, RRT

Written by:

John Landry, BS, RRT

John Landry is a registered respiratory therapist from Memphis, TN, and has a bachelor's degree in kinesiology. He enjoys using evidence-based research to help others live a healthier life.