Vitamin B12 on a Plant-Based Diet: The Non-Negotiable One

Written by the MetricFit Research Team | October 11, 2026

Most nutrient gaps on plant-based diets can be managed with food choices. Vitamin B12 is the exception — reliable plant sources essentially do not exist.

Why B12 is different

B12 is produced by microorganisms. Fortified foods and supplements are the only dependable sources on a vegan diet. Untreated deficiency can cause megaloblastic anemia and, over time, neurological damage — some of which may not fully reverse.

What the research recommends

The Academy of Nutrition and Dietetics position paper on vegetarian diets advises vegans to consume fortified foods or supplements regularly. Adequate intake helps reduce tiredness and fatigue and supports normal red blood cell formation (EFSA-authorized functions).

Practical schedule

• Cyanocobalamin or methylcobalamin both work; cyanocobalamin is the most studied and stable form.
• Common adult maintenance patterns: 25–100 mcg daily, or 1000 mcg 2–3 times per week.
• If you take metformin or long-term acid reducers, ask your doctor to monitor B12 — both medications lower absorption.