What does lack of vitamin B12 make you feel like?

January 1, 2026 •

3 min read

Did you know that your body can store vitamin B12 for several years, so a deficiency can develop very slowly and go unnoticed? This gradual onset is why many people wonder exactly what does lack of vitamin B12 make you feel like, as symptoms can be subtle and easily overlooked in the beginning.

Quick Summary

A B12 deficiency can cause a variety of symptoms, from extreme fatigue, weakness, and mood changes to neurological issues like tingling, numbness, and balance problems. Recognizing these signs early is crucial to prevent more serious complications.

Key Points

Gradual Onset: Symptoms of B12 deficiency often develop slowly over months or years, making them easy to miss early on.
Widespread Effects: A lack of vitamin B12 can affect your energy levels, mood, memory, nerves, and even your skin.
Neurological Risks: Untreated B12 deficiency can lead to serious and potentially irreversible nerve damage, including tingling, numbness, and difficulty with balance.
Diagnosis is Key: Blood tests for B12, methylmalonic acid, and homocysteine are used to confirm a diagnosis, especially when B12 levels are borderline.
Treatment Options: Depending on the cause, B12 deficiency is treated with either oral supplements or intramuscular injections to replenish levels.
High-Risk Groups: Vegans, older adults, individuals with autoimmune diseases, and those who have had gastric surgery are particularly vulnerable to deficiency.

The Role of Vitamin B12 in Your Body

Vitamin B12, also known as cobalamin, is a water-soluble vitamin vital for DNA synthesis, red blood cell formation, and maintaining a healthy nervous system. A lack of sufficient B12 disrupts these processes, leading to various symptoms that can develop gradually as the body's stores deplete.

Common Physical Symptoms

One of the most common signs of B12 deficiency is extreme fatigue and weakness, often stemming from megaloblastic anemia. This anemia impairs the body's ability to produce healthy red blood cells for oxygen transport.

Other physical symptoms may include:

Pale or yellowish skin
Heart palpitations and shortness of breath
A sore and red tongue
Weight loss and loss of appetite

Neurological and Psychological Symptoms

B12 deficiency can also significantly impact neurological and mental health, sometimes before physical symptoms appear.

These symptoms can manifest as:

Numbness or tingling, particularly in the hands and feet, indicating nerve damage.
Memory problems, confusion, and difficulty concentrating.
Mood changes, including depression and anxiety.
Issues with balance and coordination.
Rarely, vision problems.

Causes and Risk Factors

A B12 deficiency can result from insufficient dietary intake or problems with absorption.

Key causes and risk factors include:

Dietary restrictions: Vegan or vegetarian diets are higher risk as B12 is mainly in animal products.
Pernicious anemia: An autoimmune condition affecting the absorption of B12.
Malabsorption: Conditions like Crohn's or celiac disease can hinder B12 absorption.
Surgery: Gastric procedures can affect B12 processing.
Medications: Some drugs, such as metformin, can lower B12 levels.
Age: Older adults may have reduced ability to absorb B12.

B12 vs. Folate Deficiency: A Comparison

B12 and folate deficiencies share symptoms like fatigue and anemia, but differ crucially in neurological effects.


Feature	Vitamin B12 Deficiency	Folate (B9) Deficiency
Neurological Symptoms	Can cause nerve damage.	Typically absent.
Anemia Type	Megaloblastic anemia.	Megaloblastic anemia.
Main Sources	Animal products.	Leafy greens, fruits.
Diagnostic Marker	Elevated methylmalonic acid (MMA).	MMA levels normal.
Masking Effect	Folic acid can mask B12 deficiency while nerve damage progresses.	B12 does not mask folate deficiency.

Diagnosing and Treating B12 Deficiency

Diagnosis involves blood tests to check B12 levels and other markers like MMA. Early diagnosis is vital to prevent permanent neurological damage.

Treatment options include:

Oral supplements for milder, diet-related cases.
Intramuscular injections for severe deficiency or malabsorption.
Dietary adjustments to include B12-rich foods.

Conclusion

Ignoring the early signs of a B12 deficiency can lead to serious and potentially irreversible health complications, particularly affecting the nervous system. From persistent fatigue and mood changes to pins and needles and cognitive issues, the symptoms of low vitamin B12 are varied and can mimic other conditions. If you experience any of these signs, especially if you are in a high-risk group such as a vegan, an older adult, or someone with a digestive disorder, it is essential to consult a healthcare provider for a proper diagnosis and treatment plan. Early intervention is key to restoring your health and preventing long-term damage. For more information on vitamin B12 deficiency and its potential complications, consult a healthcare professional or reliable resource like the National Health Service (NHS).

Frequently Asked Questions

The most common symptom of low vitamin B12 is extreme fatigue or a persistent lack of energy. This is often caused by megaloblastic anemia, which results from the body's inability to produce enough healthy red blood cells.

Yes, a B12 deficiency can cause psychological symptoms. These can include mild depression, anxiety, irritability, and in severe cases, more significant issues like confusion, memory loss, and even psychosis.

Yes, a deficiency can cause a neurological symptom known as paraesthesia, which is a 'pins and needles' or tingling sensation. It often affects the hands and feet and is a result of nerve damage.

Because the body stores large amounts of B12 in the liver, it can take years for symptoms to appear after intake or absorption drops. The onset of symptoms is typically slow and gradual.

High-risk groups include older adults (over 65), people on a strict vegan or vegetarian diet, individuals with pernicious anemia, and those with gastrointestinal conditions like Crohn's or celiac disease.

While both can cause anemia and fatigue, B12 deficiency is distinct because it specifically causes neurological damage that does not occur with folate deficiency. Supplementing with folic acid can even mask a B12 deficiency while nerve damage continues to progress.

Treatment depends on the cause and severity. It can involve high-dose oral supplements for dietary deficiencies, or regular intramuscular injections for malabsorption issues like pernicious anemia.