What symptoms do you have if you are lacking B12?

December 18, 2025 •

3 min read

According to the National Institutes of Health, vitamin B12 deficiency can often cause fatigue and weakness, alongside a host of other symptoms. It's crucial to understand what symptoms you have if you are lacking B12, as this can affect your nervous system and overall health.

Quick Summary

A lack of vitamin B12 can manifest through physical, neurological, and psychological signs, including persistent fatigue, numbness, memory issues, and mood changes. Symptoms may appear gradually and worsen over time, impacting nerve function and red blood cell production.

Key Points

Fatigue and Weakness: Persistent tiredness and a lack of energy are primary indicators of a B12 deficiency.
Neurological Issues: Numbness, tingling, balance problems, and memory loss can signal nerve damage due to low B12.
Mood and Cognitive Changes: Deficiency can cause irritability, depression, confusion, and other psychological or cognitive problems.
Anemia-Related Signs: Pale or yellow skin, shortness of breath, and a fast heartbeat are common signs of megaloblastic anemia caused by low B12.
Oral Symptoms: A smooth, red tongue (glossitis) and mouth ulcers can be physical signs of a deficiency.
Risk Factors: Vegans, vegetarians, older adults, and those with certain digestive disorders or taking specific medications are at higher risk.
Diagnosis is Key: Symptoms are often subtle and can mimic other conditions, requiring blood tests for an accurate diagnosis.
Treatment Options: Depending on the cause, treatment can include supplements (oral, nasal) or regular injections.

The Importance of Vitamin B12

Vitamin B12, or cobalamin, is a vital nutrient essential for several critical bodily functions. It plays a key role in making DNA, the genetic material in all cells, and is crucial for keeping your body's blood and nerve cells healthy. A deficiency can lead to a range of problems, from mild discomfort to severe, irreversible damage if left untreated. The body stores B12 in the liver for several years, so symptoms can take a long time to develop, making it a 'sneaky' condition to detect.

Common Symptoms of B12 Deficiency

Symptoms of a vitamin B12 deficiency can be subtle at first and progress slowly. They can be categorized into physical, neurological, and psychological manifestations, such as fatigue, weakness, numbness or tingling in the hands and feet, difficulty walking, vision problems, muscle weakness, cognitive impairment, mood changes, confusion, paranoia, and delusions. Additional physical signs may include pale or jaundiced skin, a sore and red tongue, mouth ulcers, gastrointestinal issues like nausea, vomiting, diarrhea, loss of appetite, unintended weight loss, and headaches.

Causes of B12 Deficiency

Several factors can cause a B12 deficiency, including inadequate intake, malabsorption, and underlying medical conditions. Risk factors include dietary restrictions like veganism, pernicious anemia, gastritis, gastrointestinal surgery, digestive diseases such as Crohn's and celiac disease, aging, and certain medications.

B12 vs. Iron Deficiency: A Comparison

While both B12 and iron deficiency can cause anemia and lead to fatigue, they are distinct conditions. Key differences include the type of anemia (macrocytic for B12, microcytic for iron), the presence of neurological signs (common with B12, not typically with iron), and specific physical symptoms like glossitis (B12) versus brittle nails (iron). Both can cause a fast heartbeat, and the causes differ significantly, ranging from malabsorption or dietary restrictions for B12 to blood loss or poor absorption for iron.

Diagnosis and Treatment

Diagnosing a B12 deficiency can be challenging due to gradual onset and non-specific symptoms. Diagnosis typically involves blood tests to check B12 levels. Treatment depends on the cause and severity and may include oral supplements or injections, particularly for malabsorption issues. Early intervention is important as long-term nerve damage may be irreversible.

Conclusion

Recognizing what symptoms you have if you are lacking B12 is the first step toward effective management. The array of potential issues highlights the vitamin's widespread importance. As many symptoms overlap with other conditions, consulting a healthcare professional for a proper diagnosis is crucial. While dietary changes and supplements can address many cases, some individuals may require lifelong treatment to avoid severe complications. Early detection and intervention are key to preventing permanent nerve damage and other serious health consequences.

Preventing B12 Deficiency

Preventing B12 deficiency involves ensuring adequate intake, especially for high-risk groups. Good sources include meat, fish, dairy, and eggs. Fortified foods like cereals and plant-based milks are also reliable options. Individuals with malabsorption issues should consult a doctor for a long-term treatment plan. For detailed dietary information, the {Link: Dietary Guidelines for Americans https://www.dietaryguidelines.gov/} provides relevant guidance.

Frequently Asked Questions

While symptoms vary, one of the earliest signs of a B12 deficiency can be a persistent feeling of extreme tiredness or a lack of energy, often associated with anemia.

Yes, a B12 deficiency can cause a range of psychological symptoms, including increased irritability, anxiety, and depression.

Natural sources of B12 include meat (especially beef liver and clams), fish, eggs, and dairy products. Fortified foods like cereals, nutritional yeast, and some plant-based milks are also excellent sources.

Symptoms can develop very slowly, often over several years. This is because the body stores a significant amount of B12 in the liver, which can delay the onset of a noticeable deficiency.

If left untreated for an extended period, B12 deficiency can cause permanent neurological damage, affecting the nervous system and potentially leading to irreversible nerve problems.

No, they are different conditions. While both can cause fatigue and anemia, B12 deficiency can lead to a specific type of anemia (macrocytic) and is more commonly associated with neurological symptoms like nerve damage.

Risk groups include older adults, people on strict vegan or vegetarian diets, individuals with malabsorption issues (like pernicious anemia, Crohn's, or celiac disease), and those who have had gastrointestinal surgery.