Worried About Vitamin B12? Why You'll Want to Supplement

(Updated 08-10-26)

Vitamin B12 deficiency can affect both plant-based and non-plant-based eaters, although the reasons may differ. People eating a vegan or fully plant-based diet need to pay particular attention to getting a reliable source of B12, while other people may have difficulty absorbing it.

WHAT IS VITAMIN B12?

Vitamin B12 is an essential water-soluble vitamin that’s important for red blood cell formation, nervous system function, and DNA synthesis.

Unlike many nutrients that are plentiful in a whole-food, plant-based diet, vitamin B12 is not naturally found in reliable amounts in plant foods. That’s why people who eat a vegan or fully plant-based diet need to make sure they’re getting B12 from fortified foods or a supplement.

Absorbing B12 also involves several steps. Stomach acid helps release naturally occurring B12 from food, and a protein produced in the stomach called intrinsic factor helps the body absorb it in the small intestine. Problems anywhere along this process can contribute to a deficiency.

WHAT ARE SYMPTOMS OF B12 DEFICIENCY?

Vitamin B12 deficiency can develop gradually because the body stores B12, sometimes allowing a deficiency to go unnoticed for quite some time.

Possible signs and symptoms include:

Fatigue or weakness
Megaloblastic anemia
Pale skin
Loss of appetite or unexplained weight loss
A sore or inflamed tongue
Numbness or tingling in the hands and feet
Problems with balance or walking
Memory or other cognitive changes

Neurological symptoms can occur even without anemia, and prolonged B12 deficiency can sometimes cause irreversible nerve damage. That’s one reason prevention is so important.

WHY YOU MAY BE DEFICIENT

As it relates to B12 deficiency, it’s actually common for plant-based and meat eaters alike to experience it. Let’s take a look at four reasons people become deficient in B12:

Plant Foods Aren’t a Reliable Source of B12

Unlike many nutrients that are abundant in a whole-food, plant-based diet, vitamin B12 isn’t naturally found in reliable amounts in plant foods. Some plant-based foods, such as certain plant milks, nutritional yeast, and breakfast cereals, are fortified with B12, but the amount varies by product.

Soil on vegetables, organic produce, fermented foods, and other unfortified plant foods shouldn’t be relied upon as dependable sources of vitamin B12.

Some People Have Trouble Absorbing B12

Diet isn’t the only reason someone can become deficient in vitamin B12. Absorption may become more difficult with age, and conditions such as pernicious anemia, gastrointestinal diseases, or previous gastrointestinal surgery can interfere with B12 absorption.

Certain medications, including metformin and long-term use of acid-reducing medications, may also contribute to low B12 levels.

Testing for Vitamin B12

A blood test can help identify a vitamin B12 deficiency, although a serum B12 result doesn’t always tell the whole story. If levels are borderline or symptoms suggest a possible deficiency, a healthcare provider may recommend additional testing, such as methylmalonic acid (MMA).

WHY YOU’LL WANT A RELIABLE SOURCE OF B12

If you’re eating a vegan or fully plant-based diet, vitamin B12 is one nutrient you don’t want to leave to chance.

Rather than waiting until your B12 level becomes low, the goal is to prevent deficiency by consistently getting B12 from fortified foods or a supplement.

The adult Recommended Dietary Allowance for vitamin B12 is 2.4 micrograms per day, but don’t let the much larger numbers on B12 supplements confuse you. The percentage of B12 absorbed decreases as supplemental doses get larger, which is one reason supplements often contain considerably more than the daily requirement.

One commonly used option is cyanocobalamin, a stable and well-studied form of vitamin B12. Dr. Michael Greger of NutritionFacts.org currently recommends that adults under age 65 get at least 50 mcg of supplemental cyanocobalamin daily or 2,000 mcg once per week, or get adequate B12 from fortified foods. Needs may differ for older adults and for people who have difficulty absorbing B12.

Individual needs can be different, particularly for older adults and people who already have a deficiency, pernicious anemia, gastrointestinal conditions, previous gastrointestinal surgery, or medications that interfere with B12 absorption. Treatment for an existing deficiency is also different from routine supplementation intended to prevent one.

The important takeaway is simple: a well-planned whole-food, plant-based diet can provide almost everything you need, but vitamin B12 deserves special attention. Make sure you have a reliable source rather than waiting for symptoms or a deficiency to develop.

Discover More

To read more about supplementing if you’re eating a vegan or plant-based diet, read my article, “Should Vegans Be Taking Supplements? And Which Ones?”

RESOURCES

To learn more and bolster your confidence in making the right decision about Vitamin B12 and supplementation, I encourage you to do your own research. Here are a few resources I think you’ll find helpful: