What Happens If I Don't Take My B12? Unveiling the Risks of Deficiency

October 9, 2025 •

3 min read

The human body can store several years' worth of vitamin B12 in the liver, but what happens if I don't take my B12 and these reserves run dry? The consequences of an untreated deficiency are far more severe than simple fatigue and can lead to irreversible damage to your nerves and brain.

Quick Summary

An untreated deficiency of vitamin B12 can lead to serious health problems, including permanent nerve damage, cognitive decline, and megaloblastic anemia over time.

Key Points

Essential for Function: Vitamin B12 is vital for making DNA, producing healthy red blood cells, and maintaining a healthy nervous system.
Long Incubation Period: The body can store B12 for several years, which means symptoms can develop very gradually and may not appear for a long time.
Severe Risks: Untreated deficiency can lead to irreversible neurological damage, cognitive decline, and megaloblastic anemia.
Diverse Symptoms: Look out for both physical signs like fatigue and a sore tongue, as well as neurological and psychological issues like tingling, poor balance, depression, and memory loss.
Beyond Diet: Malabsorption issues, particularly pernicious anemia and age-related changes, are a major cause of deficiency, not just inadequate dietary intake.
Treatment is Critical: Early diagnosis and appropriate treatment with supplements or injections can halt the progression of symptoms and prevent permanent damage.
Folate Can Mask B12 Issues: Treating anemia with folate alone can mask an underlying B12 deficiency, allowing neurological damage to continue unchecked.

The Crucial Role of Vitamin B12

Vitamin B12, also known as cobalamin, is a water-soluble vitamin essential for vital bodily functions. It is crucial for DNA synthesis, metabolism, red blood cell production, and maintaining a healthy nervous system by forming myelin.

Mainly found in animal products, B12 is stored in the liver, meaning a deficiency can take years to show. Once stores are low, health issues can arise and cause lasting harm.

Progressive Symptoms of B12 Deficiency

Symptoms of B12 deficiency appear gradually and vary, often mimicking other conditions. Early signs include fatigue, weakness, a sore tongue, pale skin, and digestive issues.

Neurological and psychological effects are significant and can occur before anemia. These effects can range from mild to severe.

Neurological Symptoms May Include:

Pins and needles or numbness in limbs.
Difficulty with balance and coordination.
Vision problems.
Cognitive decline, affecting memory and concentration.
Psychological problems like mood swings, depression, and paranoia.

The Long-Term Consequences of Untreated Deficiency

Untreated B12 deficiency can cause severe and sometimes irreversible problems. Chronic nerve damage can lead to permanent peripheral neuropathy and spinal cord degeneration. Megaloblastic anemia can strain the heart, potentially leading to heart failure. In pregnant women, it increases the risk of birth defects. Early treatment is vital to prevent these issues.

What Causes a B12 Deficiency?

Causes of B12 deficiency go beyond diet, often involving issues with absorption, which requires intrinsic factor produced in the stomach.

Common Causes and Risk Factors

Dietary insufficiency: Common in vegans and some vegetarians without supplements or fortified foods.
Pernicious anemia: An autoimmune condition preventing intrinsic factor production.
Age: Older adults may have reduced stomach acid, affecting B12 release from food.
Gastrointestinal surgery: Procedures can impair intrinsic factor production or absorption.
Digestive disorders: Conditions like Crohn's and celiac disease hinder absorption.
Medications: Certain drugs can interfere with B12 absorption.

B12 vs. Folate Deficiency: A Crucial Distinction

Both B12 and folate deficiencies can cause megaloblastic anemia, but only B12 deficiency leads to severe neurological problems. Folate supplements can mask B12 deficiency's anemia without fixing nerve damage. Thus, confirming the specific deficiency before treatment is essential.


Feature	Vitamin B12 Deficiency	Folate (B9) Deficiency
Primary Cause	Poor absorption (e.g., pernicious anemia), dietary lack (vegan/vegetarian diet)	Inadequate dietary intake (e.g., lack of green leafy vegetables), poor absorption
Symptom Onset	Gradual onset; symptoms can take years to appear due to liver storage	Quicker onset, as body stores are smaller
Neurological Damage	Can cause severe and often irreversible nerve damage and cognitive decline	Does not typically cause nerve damage
Megaloblastic Anemia	Yes, red blood cells are abnormally large	Yes, red blood cells are abnormally large
Homocysteine Level	Elevated	Elevated
Methylmalonic Acid (MMA) Level	Elevated	Normal
Treatment Risk	Folic acid can mask symptoms and worsen neurological damage if B12 is not also treated	Supplementation with folic acid effectively treats the deficiency

Conclusion: Don't Ignore the Signs

Ignoring vitamin B12 deficiency is a serious health risk, potentially causing permanent nervous system and brain damage. Symptoms progress slowly, making early recognition and diagnosis vital. Regardless of the cause, treatment with supplements or injections can correct the deficiency and stop symptom progression. Those at risk, including vegans, older adults, and individuals with malabsorption, should consider monitoring and supplementation to maintain health.

For more detailed information on vitamin B12 deficiency, including diagnosis and treatment options, please consult the resources available from the National Institutes of Health (NIH).(https://ods.od.nih.gov/factsheets/VitaminB12-Consumer/)

Frequently Asked Questions

Yes, a vitamin B12 deficiency can cause a wide range of psychological symptoms, including depression, irritability, and even paranoia in severe cases.

Diagnosis typically involves a blood test to measure vitamin B12 levels. Sometimes, additional tests for methylmalonic acid (MMA) and homocysteine may be used, as these levels rise with deficiency.

If caught early, some neurological symptoms may be reversible with treatment. However, long-term, untreated nerve damage can become permanent.

Vitamin B12 is primarily found in animal products like meat, fish, eggs, and dairy. Vegans can get it from fortified foods such as cereals and plant-based milks, or from supplements.

Groups at higher risk include older adults, people with digestive disorders like Crohn's or celiac disease, individuals who have had gastrointestinal surgery, vegans and vegetarians, and those with pernicious anemia.

Yes, it is possible. Neurological and psychological symptoms can sometimes appear before the development of megaloblastic anemia, especially in cases of more severe deficiency.

Pernicious anemia is an autoimmune condition where the body cannot make intrinsic factor, a protein necessary to absorb vitamin B12 from the gut. It is a common cause of B12 deficiency.