Corinne Lough
Health Writer & Founder, Medasia
Last updated: August 2026 · Content based on NIH data · For informational purposes only — not medical advice
Most people associate anemia with iron deficiency — but vitamin B12 deficiency is another major cause that is often overlooked. Understanding the relationship between B12 and anemia can help you identify the right solution for your symptoms.
What Is Vitamin B12 Deficiency Anemia?
Vitamin B12 is essential for the production of healthy red blood cells. When B12 levels are too low, the body produces red blood cells that are abnormally large and unable to function properly — a condition called megaloblastic anemia or pernicious anemia. These oversized cells cannot carry oxygen efficiently, leading to symptoms similar to iron deficiency anemia. (NIH)
Symptoms of B12 Deficiency Anemia
- Fatigue and weakness
- Pale or jaundiced skin
- Shortness of breath
- Numbness or tingling in hands and feet (nerve damage)
- Difficulty walking or balance problems
- Cognitive changes — memory problems, difficulty concentrating
- Swollen or inflamed tongue (glossitis)
- Mood changes, including depression
Who Is at Risk of B12 Deficiency?
- Vegans and vegetarians — B12 is found almost exclusively in animal products
- Older adults — reduced stomach acid impairs B12 absorption with age
- People with pernicious anemia — an autoimmune condition that prevents B12 absorption
- Those taking metformin or proton pump inhibitors — these medications reduce B12 absorption
- People with gastrointestinal conditions — Crohn’s disease, celiac disease
B12 vs. Iron Deficiency Anemia: Key Differences
| Feature | Iron Deficiency Anemia | B12 Deficiency Anemia |
|---|---|---|
| Red blood cell size | Small (microcytic) | Large (macrocytic) |
| Neurological symptoms | Rare | Common (tingling, memory loss) |
| Main dietary sources | Meat, beans, leafy greens | Meat, fish, dairy, eggs |
| Treatment | Iron-rich diet + supplements | B12 supplements or injections |
Source: NIH Office of Dietary Supplements
Food Sources of Vitamin B12
- Clams — highest natural source (~84 mcg per 3 oz)
- Beef liver — ~70 mcg per 3 oz
- Salmon and tuna — ~4–9 mcg per 3 oz
- Eggs — ~0.6 mcg per egg
- Dairy products — ~1 mcg per cup of milk
- Fortified cereals and plant milks — varies by brand
Note: If you also have iron deficiency, see our iron-rich foods list for a complete guide to boosting both nutrients through diet.
Treatment Options
B12 deficiency anemia is treated with vitamin B12 supplementation — either oral supplements (for mild deficiency) or intramuscular injections (for severe deficiency or pernicious anemia). Dietary changes alone may not be sufficient if absorption is impaired. Always consult a doctor for diagnosis and treatment.
Related Articles
- Iron-Rich Foods List: 50+ Foods With Iron and Serving Sizes
- 7-Day Iron-Rich Meal Plan for Anemia
- 11 Best Drinks High in Iron for Anemia Patients
- Low Hemoglobin: Simple Tips for Older Adults
- Best Home Hemoglobin Meter: 2026 Buyer's Guide
References
- NIH Office of Dietary Supplements. Vitamin B12 — Fact Sheet for Health Professionals. ods.od.nih.gov
- Mayo Clinic. Vitamin deficiency anemia. mayoclinic.org
This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional for diagnosis and treatment.