Vitamin B12 Deficiency: Key Signs, Nerve Damage, Anemia, and Who Should Get Tested

Feeling unusually tired, foggy, or off balance can be easy to blame on stress, lack of sleep, or “just getting older.” But for some people, these symptoms trace back to a surprisingly common and often overlooked cause: vitamin B12 deficiency.

Vitamin B12 plays a central role in nerve health, red blood cell formation, and brain function. When levels are low, the effects can show up slowly and in many different ways—from subtle memory changes to clear signs of anemia. Because symptoms overlap with many other conditions, B12 deficiency can go unnoticed for a long time.

This guide walks through the signs of vitamin B12 deficiency, focusing on nerve symptoms, anemia, and who may benefit from testing. It’s designed to help you understand what B12 does in the body, what to watch for, and how people commonly navigate testing and treatment decisions with their healthcare providers.

What Is Vitamin B12 and Why Does It Matter?

Vitamin B12 (also called cobalamin) is an essential nutrient, meaning the body cannot make it and must get it from food or supplements. It is involved in several key processes:

• Red blood cell production
• Maintaining the protective coating (myelin) around nerves
• Supporting normal brain and cognitive function
• Helping with DNA synthesis and cell division

Because B12 touches so many systems, a deficiency can look very different from one person to another. Some notice changes in mood or memory; others see pale skin, weakness, or tingling in the hands and feet.

The body stores some B12, especially in the liver, so deficiency can develop slowly over months or years. That slow onset is part of the reason it is sometimes overlooked.

Common Signs and Symptoms of Vitamin B12 Deficiency

Vitamin B12 deficiency does not have one single “classic” presentation. Instead, it often involves a cluster of symptoms affecting blood, nerves, mood, and energy.

General Symptoms: The Early, Nonspecific Clues

These symptoms are common to many health conditions, so they do not automatically point to B12. However, they can be part of the picture:

• Fatigue or low energy, even after rest
• Weakness or reduced stamina
• Shortness of breath with usual activities
• Dizziness or lightheadedness
• Pale or slightly yellow skin
• Reduced appetite or mild weight changes

Some people also describe feeling “off” in a vague way: more tired, less focused, and not quite themselves mentally or physically.

Cognitive and Mood Changes

Because vitamin B12 supports brain function, low levels may be associated with:

• Difficulty concentrating or “brain fog”
• Memory lapses, such as forgetting recent conversations or misplacing items more often
• Slower thinking or mental processing
• Irritability, low mood, or feeling unusually down
• Changes in behavior or personality that seem out of character

These changes can easily be mistaken for stress, depression, or age-related memory issues. In some people with underlying depression or anxiety, B12 deficiency may add another layer of cognitive or mood symptoms.

Nerve Symptoms of Vitamin B12 Deficiency

One of the most important—and sometimes lasting—effects of B12 deficiency involves the nervous system. B12 is needed to maintain myelin, the insulating layer that protects nerves and helps them transmit signals efficiently. When B12 is too low, nerve function can be disrupted.

Sensory Changes: Tingling, Numbness, and Burning

A common set of nerve-related symptoms includes:

• Tingling or “pins and needles” (often in the hands, feet, or legs)
• Numbness, especially in a “stocking and glove” pattern (affecting hands and feet first)
• Burning, buzzing, or electric-shock-like sensations
• Increased sensitivity to touch in affected areas

These symptoms are often more noticeable at rest, such as when lying in bed, and may gradually worsen if deficiency persists.

Balance, Coordination, and Muscle Issues

As nerve damage progresses, it may affect movement and coordination:

• Unsteadiness while walking, especially in the dark or on uneven ground
• Poor balance or feeling wobbly when standing still
• Clumsiness, tripping more often, or difficulty with fine motor tasks (buttoning clothes, writing, etc.)
• Muscle weakness, especially in the legs

In some cases, these changes can be mistaken for neurological conditions unrelated to nutrition. This is one reason clinicians often consider B12 levels when evaluating unexplained balance or coordination problems.

Vision and Reflex Changes

Less commonly, vitamin B12 deficiency can be associated with:

• Blurred or reduced vision
• Changes in reflexes, such as reduced ankle reflexes

Not everyone will experience these symptoms, and when they do occur, they usually appear alongside other neurological or systemic signs.

⚠️ Important note: Nerve damage related to long-standing, severe B12 deficiency may not fully reverse, even when levels are corrected. This is why many healthcare professionals emphasize early recognition and testing in at-risk individuals.

Anemia and Blood-Related Signs of Vitamin B12 Deficiency

Vitamin B12 is essential for red blood cell formation. Without adequate B12, the bone marrow produces fewer and often larger-than-normal red blood cells that do not function properly—a pattern often referred to as megaloblastic anemia.

How Anemia Shows Up in Everyday Life

When red blood cells are not working well, the body has more difficulty delivering oxygen to tissues. This can lead to:

• Tiredness and weakness
• Shortness of breath, especially with exertion
• Rapid or pounding heartbeat (palpitations)
• Headaches
• Feeling faint or lightheaded

These symptoms overlap with many other types of anemia and health issues. Blood testing is typically used to distinguish B12-related anemia from other causes.

Physical Signs of Anemia

Some people with anemia due to B12 deficiency may also notice:

• Pale skin, especially visible on the face, inside the eyelids, or on the palms
• Mild jaundice (a slightly yellow tinge to the skin or eyes)
• Smooth, red, or sore tongue (often described as “beefy red”)
• Mouth ulcers or cracks at the corners of the mouth

These signs can also be influenced by other nutritional deficiencies, underlying conditions, or lifestyle factors.

Digestive, Oral, and Other Possible Symptoms

Vitamin B12 deficiency can also show up in other systems beyond nerves and blood.

Digestive and Appetite Changes

Some individuals report:

• Loss of appetite
• Nausea or digestive discomfort
• Mild diarrhea or constipation

These symptoms are nonspecific and can occur in many gastrointestinal conditions, but they may be part of the overall picture of B12 deficiency.

Oral Changes: Tongue and Mouth

Low B12 levels are sometimes associated with changes in the mouth, such as:

• Glossitis – a smooth, shiny, or sore tongue
• Burning sensations in the tongue or mouth
• Mouth ulcers

People often describe increased sensitivity when eating spicy or acidic foods.

Mood and Sleep

Because vitamin B12 is involved in brain chemistry, lower levels may be linked with:

• Low mood or depressive symptoms
• Heightened anxiety or irritability
• Disturbed sleep or feeling unrefreshed even after adequate sleep time

These symptoms are not specific to B12 deficiency, but they may prompt clinicians to include B12 levels in the evaluation, especially when combined with physical signs.

Who Is Most at Risk for Vitamin B12 Deficiency?

Anyone can develop B12 deficiency, but certain groups have a higher likelihood based on how B12 is absorbed, what they eat, and their underlying health.

1. People With Low B12 Intake (Diet-Related)

B12 is found naturally almost exclusively in animal-derived foods, including:

• Meat and poultry
• Fish and shellfish
• Eggs
• Dairy products

People who eat little or no animal products may have lower B12 intake over time, especially if they do not use fortified foods or supplements. Groups commonly considered at higher risk include:

• Vegans (no animal products)
• Some vegetarians, depending on how much dairy and eggs they consume
• Individuals with very restricted diets for cultural, religious, or personal reasons

Fortified foods and supplements are commonly used strategies to maintain adequate B12 intake in these groups.

2. Older Adults

As people age, several changes can affect B12 status:

• Reduced stomach acid production, which plays a role in releasing B12 from food
• Higher likelihood of chronic stomach or intestinal conditions
• Increased use of certain medications that can affect B12 absorption

These factors may lead to gradual depletion of B12 stores. As a result, B12 levels are sometimes checked more frequently in older adults, especially when they show symptoms like fatigue, cognitive changes, or balance problems.

3. People With Digestive or Autoimmune Conditions

Several conditions can interfere with B12 absorption in the stomach or intestines:

• Pernicious anemia – an autoimmune condition where the body attacks cells that produce intrinsic factor, a protein needed for B12 absorption
• Chronic gastritis or atrophic gastritis
• Celiac disease
• Inflammatory bowel diseases, such as Crohn’s disease, particularly when the lower small intestine is affected or removed
• History of stomach or intestinal surgery, including weight-loss (bariatric) procedures

In these situations, even a diet that includes B12-rich foods may not be enough because the body cannot absorb the vitamin effectively.

4. People Taking Certain Medications Long-Term

Some commonly used medications may reduce B12 absorption when used over extended periods, such as:

• Acid-reducing medications, including certain proton pump inhibitors and H2 blockers
• Metformin, a widely used medication for managing blood sugar

Not everyone taking these medications develops B12 deficiency, but the possibility is considered, especially if symptoms suggest low B12.

5. Individuals With Alcohol Misuse or Poor Overall Nutrition

Heavy or long-term alcohol use and generally poor dietary intake can impact:

• Nutrient absorption in the gut
• Liver function and nutrient storage
• Overall vitamin and mineral balance

In these contexts, B12 deficiency may coexist with other nutritional deficiencies, which can further complicate symptoms and laboratory findings.

Who Should Consider Getting Tested for Vitamin B12 Levels?

Only a healthcare professional can evaluate all the relevant factors and decide whether testing is appropriate. However, several patterns commonly prompt B12 testing as part of a broader evaluation.

Situations Where B12 Testing Is Commonly Considered

People are often tested for vitamin B12 deficiency when they experience:

• Unexplained fatigue, weakness, or dizziness
• Signs of anemia on a routine blood count
• Numbness, tingling, or burning in hands and feet
• Balance problems or difficulty walking
• Unexplained memory issues, confusion, or mood changes
• Glossitis or frequent mouth ulcers

Testing may also be considered if a person:

• Follows a vegan or very restricted vegetarian diet
• Has a known malabsorption condition (such as celiac disease or pernicious anemia)
• Has had parts of the stomach or small intestine surgically removed
• Uses certain medications long-term, as mentioned above

In many cases, B12 testing is done alongside other blood tests to build a more complete picture of health.

How Vitamin B12 Deficiency Is Typically Diagnosed

Diagnosis usually involves a combination of history, physical examination, and blood tests. While specific protocols can vary, the general approach often includes:

1. Medical History and Physical Examination

A health professional may ask about:

• Dietary patterns (animal product intake, use of fortified foods or supplements)
• Digestive health (abdominal pain, chronic diarrhea, weight changes)
• Neurological symptoms (numbness, tingling, weakness, balance issues)
• Mood and cognitive changes
• Medication use
• Family or personal history of autoimmune or gastrointestinal conditions

A physical exam can reveal signs like pale skin, an enlarged liver, changes in reflexes, or a smooth, sore tongue.

2. Blood Tests

Commonly used tests may include:

• Complete blood count (CBC) – to look for anemia and changes in red blood cell size and shape
• Serum vitamin B12 level – to estimate B12 status in the blood
• In some cases, additional markers that relate to B12 function may be checked to clarify borderline results

In situations where pernicious anemia is suspected, specific tests related to intrinsic factor or stomach function may also be used.

Testing strategies and interpretation can differ depending on symptoms, age, and overall health.

Why Early Recognition of Vitamin B12 Deficiency Matters

One of the key concerns with B12 deficiency is that nerve-related symptoms may become long-lasting if the deficiency continues unchecked. In milder or shorter-term cases, symptoms may improve once levels are restored. However, delayed recognition can mean:

• Ongoing or progressive numbness and tingling
• Persistent balance problems or difficulty walking
• Lasting changes in cognitive function

Beyond the nervous system, untreated B12 deficiency can contribute to anemia, extreme fatigue, and reduced quality of life.

Because many of these symptoms overlap with other conditions, B12 testing is often one of several tools that clinicians use to rule out or confirm possible causes.

Everyday Sources of Vitamin B12 and How People Maintain Their Levels

While specific treatment or supplementation decisions belong in a conversation with a healthcare professional, it can be useful to understand where B12 comes from and how people typically think about maintaining adequate levels.

Food Sources of Vitamin B12

Common dietary sources include:

• Beef, poultry, and pork
• Fish and shellfish, such as salmon, tuna, and clams
• Dairy products, including milk, yogurt, and cheese
• Eggs, particularly the yolk

Some plant-based products are fortified with vitamin B12, such as certain breakfast cereals, plant-based milks, or nutritional yeasts. Labels often indicate if B12 has been added.

How People Address or Prevent B12 Deficiency

People often discuss the following options with their healthcare providers:

• Adjusting diet to include more B12-rich foods or fortified products
• Oral supplements (tablets, capsules, lozenges)
• Injections or high-dose supplements, particularly in cases of severe deficiency or malabsorption

The best approach can depend on the underlying cause (dietary vs. absorption-related), the severity of deficiency, and a person’s overall health.

Quick-Reference Summary: Key Signs and Risk Factors for B12 Deficiency

Here is a simple table to help organize the most common signs and who might think about testing, for informational purposes only:

This table is a starting point, not a diagnostic tool. Any concerns are usually best discussed with a qualified professional who can interpret symptoms and test results together.

Practical Tips If You’re Concerned About Vitamin B12 Levels

Without offering medical advice, here are general, non-prescriptive steps people often find helpful when they are curious about B12 deficiency:

• 📝 Track your symptoms

  • Note when they started, how often they occur, and anything that makes them better or worse.
  • Include physical, mood, and cognitive changes.

• 🍽️ Review your diet

  • Consider how often you eat animal products or B12-fortified foods.
  • If you follow a vegan or mostly plant-based diet, be aware that B12 is typically limited in unfortified plant foods.

• 💊 Take inventory of your medications

  • Make a list of all prescription and non-prescription medications and supplements you use regularly.
  • Certain long-term medications are known to interact with B12 status.

• 📂 Gather your health history

  • Include any history of digestive disorders, surgery on the stomach or intestines, or autoimmune conditions.
  • Note any family history of similar conditions.

• 🩺 Seek professional input for next steps

  • Many people bring their symptom notes and questions to an appointment for discussion.
  • A professional can decide whether B12 testing fits into a broader evaluation.

These actions do not replace medical care, but they can make conversations with healthcare providers more focused and informative.

Putting It All Together

Vitamin B12 deficiency is a quiet but impactful condition that can affect blood, nerves, mood, and overall energy. Its signs are often subtle at first and can easily be mistaken for stress, aging, or unrelated health issues.

Key points to remember:

• Nerve symptoms such as tingling, numbness, and balance problems are especially important because they may become long-lasting if deficiency is severe or prolonged.
• Anemia related to B12 often shows up as fatigue, pale skin, rapid heartbeat, and shortness of breath, but these symptoms alone do not confirm the cause.
• Higher-risk groups include people with low dietary intake of B12, older adults, those with digestive or autoimmune conditions, individuals on certain long-term medications, and people with heavy alcohol use or poor nutrition.
• Testing decisions are typically based on a combination of symptoms, risk factors, and routine blood findings, guided by a healthcare professional.

By understanding how B12 works in the body and recognizing the patterns of deficiency, individuals are better equipped to ask informed questions, notice early warning signs, and participate actively in conversations about their health.