Vitamin B12, also called cobalamin, helps maintain healthy nerves, produce red blood cells, and synthesize DNA. A deficiency can cause fatigue, anemia, and neurological problems.

Low B12 may result from inadequate intake or difficulty absorbing the vitamin—even when your diet provides enough. Identifying the cause helps guide treatment.

Common Vitamin B12 Deficiency Symptoms

Symptoms can develop gradually and may include:

• Fatigue or weakness
• Numbness or tingling in the hands and feet
• Balance problems
• Memory changes or difficulty concentrating
• A sore tongue
• Loss of appetite or unexplained weight loss
• Pale skin or heart palpitations

Nerve problems can occur without anemia, so a normal red blood cell count does not rule out B12 deficiency.

What Causes B12 Deficiency?

Common causes and risk factors include:

• Low dietary intake: Vegan or vegetarian diets lacking sufficient fortified foods or supplements
• Pernicious anemia: An autoimmune condition that reduces intrinsic factor, a protein in the stomach needed for normal B12 absorption
• Digestive conditions: Crohn’s disease, celiac disease and other absorption problems.
• Stomach or intestinal surgery: Including certain weight-loss procedures
• Older age: Age-related changes can make it harder to absorb B12 from food
• Certain medications: Metformin and long-term use of acid-reducing medications can lower B12 levels

Taking these medicines does not automatically mean you need supplements. Ask your provider whether testing or supplementation is appropriate; do not stop prescribed medication on your own.

How Is Vitamin B12 Deficiency Diagnosed?

Your provider will review your symptoms, diet, medications, and medical history. Testing may include:

• Vitamin B12 level: Measures B12 in your blood
• Complete blood count (CBC): Checks for anemia and changes in blood cells
• Additional tests: May help identify an absorption problem or pernicious anemia

If your B12 result is borderline, a methylmalonic acid (MMA) test may help determine whether a deficiency is present.

How Is B12 Deficiency Treated?

Treatment depends on the cause, severity, and whether neurological symptoms are present. Options include:

• Oral B12 supplements: Appropriate for many people
• B12 injections: May be recommended for absorption issues or neurological symptoms
• Dietary changes: Help address inadequate intake.
• Long-term replacement: May be needed if the underlying cause cannot be corrected

Your provider will determine the dose, schedule, and follow-up testing. Improvement varies, and nerve symptoms may take longer to resolve. Some damage can be permanent if treatment is delayed.

Foods That Provide Vitamin B12

Reliable sources include:

• Fish, meat and poultry
• Eggs, milk and other dairy products
• Breakfast cereals fortified with B12
• Fortified nutritional yeast

Check labels to confirm fortification. Vegetables, beans, lentils, and fruit are not reliable natural sources of B12, although many provide folate and other nutrients.

Folate does not replace B12. Folic acid alone can improve anemia while masking an untreated B12 deficiency.

When to Seek Care

Schedule an evaluation for persistent fatigue, unexplained weakness, or other symptoms. Seek prompt assessment for numbness, tingling, or balance changes—early treatment can help prevent lasting complications.

Get Help for B12 Deficiency Symptoms

Feeling unusually tired or concerned about your B12 levels? Schedule a visit with tru Primary & Urgent Care to discuss your symptoms and explore testing and treatment options.