Vitamin B12 is one of the most critical nutrients for those following a vegan or vegetarian diet. Unlike other nutrients, B12 is virtually absent from plant-based foods, making supplementation a real necessity—not just a mere complement. If you are vegan or vegetarian and have not yet considered how you are meeting your needs for this nutrient, read on.

What is vitamin B12 and what is it used for?

Vitamin B12 (also known as cobalamin) is a water-soluble vitamin essential for the functioning of the nervous system, the formation of red blood cells, and DNA synthesis. The body cannot produce it on its own; it needs to obtain it from external sources, mainly animal products such as meat, fish, eggs, and dairy.

For strict vegans or vegetarians, this poses a real challenge. Most plant-based foods do not contain B12 in sufficient quantities, and those marketed as "rich in B12"—certain types of algae or nutritional yeast—do not always offer bioavailable forms of this vitamin.

Symptoms of vitamin B12 deficiency

B12 deficiency can develop slowly, sometimes over years, because the liver stores reserves that can last between 3 and 5 years. This makes it an especially insidious problem: by the time symptoms appear, the deficiency can already be severe. The most frequent warning signs are:

• Extreme fatigue and tiredness, even after adequate rest
• Tingling or numbness in hands and feet (a sign of neurological involvement)
• Difficulty concentrating and memory problems
• Megaloblastic anemia, with abnormally large and poorly functional red blood cells
• Mood changes, irritability, or depression
• Glossitis (inflamed and painful tongue)

If you have been following a vegan or vegetarian diet for some time without supplementing B12, it is most prudent to get a blood test to check your levels.

How much vitamin B12 do vegans need?

The recommended daily intake for adults is 2.4 micrograms (mcg) per day. However, for those who supplement, the usual doses are higher, because absorption varies with the frequency of intake.

The body absorbs B12 through two mechanisms: one that is highly efficient but quickly saturates (for low and frequent doses) and another through passive diffusion (for high and less frequent doses). Therefore, the amount to take depends on the supplementation schedule:

• Daily: between 25 and 100 mcg
• Two or three times a week: 500–1,000 mcg per dose
• Once a week: 2,000–2,500 mcg

There is no known risk of toxicity with high doses of vitamin B12, as excess is eliminated through urine.

Forms of vitamin B12: which one to choose?

Not all forms of B12 are the same. In the market, you will mainly find:

• Cyanocobalamin: the most studied and stable. It is the most common in supplements and very effective in preventing deficiency. A good general option.
• Methylcobalamin: an active form that does not require conversion in the body. Especially recommended for people with genetic variants that hinder folate metabolism (MTHFR variant).
• Adenosylcobalamin: also an active form, less common in oral supplements.
• Hydroxocobalamin: slower and more prolonged absorption, frequent in injectable formulations.

For most people, cyanocobalamin is the most practical and economical option. If you have a history of neurological problems or folate metabolism disorders, methylcobalamin may be more suitable.

Vitamin B12 and other key nutrients for vegans

B12 is not the only nutrient that may be scarce in a vegan diet. Along with it, it is advisable to monitor:

• Vitamin D3: essential in winter or if you spend little time in the sun. Plant-based D3 formulations (from lichen) are available. Discover it in our collection of Vitamin D3.
• Omega-3 DHA/EPA: present in oily fish, but also available in algal oil for vegans. Check our Omega-3 section.
• Iron: although present in legumes and vegetables, it is absorbed less efficiently than animal heme iron. Combining plant iron with vitamin C improves its absorption.
• Magnesium: essential for more than 300 enzymatic reactions. Deficiency is very common in the general population. Visit our Magnesium collection.

Vitamin B12 for vegans: conclusion

Vitamin B12 is probably the most important supplement for anyone following a strict vegan or vegetarian diet. Deficiency can take years to manifest, but its consequences—neurological and hematological—can be severe and sometimes irreversible. The good news is that preventing it is simple, affordable, and risk-free.

If you are not yet supplementing with vitamin B12 for vegans, now is the time to start. At AndaVida, you will find B12 supplements from trusted brands like Solgar, Solaray, and Physalis, in various formats—sublingual tablets, capsules, and more—adapted to your needs. Your nervous system will thank you.