Vitamin B12 Deficiency: Symptoms, Causes & Treatment Guide

Vitamin B12 is an essential nutrient that helps maintain healthy nerves, blood cells, and brain function. A vitamin B12 deficiency occurs when the body doesn’t get enough B12 or is unable to absorb it properly. This can lead to low B12 levels, fatigue, anemia and even long-term neurological problems if untreated.

This guide covers vitamin B12 deficiency symptoms, causes, risk factors, diagnosis, treatment, and prevention.

What is Vitamin B12 and Why Is It Important?

Vitamin B12 (cobalamin) is crucial for:

• Red blood cell formation

• Healthy nerve function

• DNA synthesis

• Brain and memory support

• Energy production

A deficiency can affect multiple body systems, which is why early detection is important.

The vitamin B12 normal range for most adults is typically 200–900 pg/mL, though it may vary by lab.

Vitamin B12 Deficiency Symptoms

Symptoms can be mild in the beginning but worsen over time if left untreated.

General Symptoms

• Constant tiredness or weakness

• Pale or yellowish skin

• Shortness of breath

• Heart palpitations

• Loss of appetite

• Weight loss

Neurological Symptoms of B12 Deficiency

Vitamin B12 plays a major role in nerve health. Low levels can cause:

• Tingling or numbness in hands and feet

• Difficulty walking or balance problems

• Muscle weakness

• Memory problems

• Poor concentration

• Mood changes (depression, irritability)

• Cognitive decline in severe cases

Other B12 Deficiency Signs

• Sore or red tongue

• Mouth ulcers

• Vision disturbances

• Dizziness

• Cold hands and feet

Causes of Vitamin B12 Deficiency

Vitamin B12 deficiency happens either due to low intake or poor absorption.

1. Dietary Deficiency

• Vegan or strict vegetarian diets

• Poor nutrition

• Elderly individuals with reduced appetite

2. Malabsorption Issues

• Pernicious anemia (autoimmune condition affecting the stomach)

• Gastric surgeries (weight loss surgery, gastrectomy)

• Crohn’s disease or celiac disease

• Chronic gastritis

• Low stomach acid (common in older adults)

3. Medications

• Metformin (used for diabetes)

• Proton pump inhibitors (PPIs)

• H2 blockers

4. Alcohol Use

Heavy alcohol consumption reduces nutrient absorption.

Low B12 Levels: Risk Factors

You’re more likely to have low B12 levels if you are:

• Over 60 years old

• Vegan/vegetarian

• Suffering from digestive disorders

• Taking long-term antacid or diabetes medication

• Pregnant or breastfeeding

• Regularly consuming alcohol

• Living with autoimmune conditions

Vitamin B12 Deficiency Diagnosis

Doctors use several tests to confirm a deficiency.

1. Blood Tests

These measure:

• Vitamin B12 levels

• Complete blood count (CBC)

• Homocysteine levels

• Methylmalonic acid (MMA) levels

2. Physical Examination

Checking for neurological symptoms and anemia signs.

3. Detailed Medical History

Diet, medications, and digestive problems help identify causes.

Vitamin B12 Deficiency Treatment

Treatment depends on the severity and underlying cause.

1. Oral Supplements

• High-dose B12 tablets (cyanocobalamin or methylcobalamin)

• Usually recommended for mild to moderate deficiency

2. Vitamin B12 Injections

Given when absorption is poor, such as in pernicious anemia or severe deficiency.
Frequency may be:

• Daily/weekly initially

• Monthly maintenance dose

3. Dietary Changes

Include B12-rich foods such as:

• Meat and poultry

• Fish (salmon, tuna)

• Eggs

• Dairy products

• Fortified cereals

• Nutritional yeast

4. Treating Underlying Conditions

Managing digestive disorders or adjusting medications improves absorption.

Prevention Tips

• Eat a diet rich in B12

• Take supplements if you follow a vegetarian/vegan diet

• Monitor B12 levels if you take metformin or antacids

• Get regular blood tests if you are at high risk