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Your Guide to B12 Supplements: Everything You Need to Know About Them

B12 is a necessary and vital nutrient that we need in our bodies. And sometimes we need extra B12 added to our diet.

By Anna Nordseth; Reviewed by Dr. Harshi Dhingra
Jul 29, 2023 3:00 PMDec 28, 2023 4:12 PM
B12 supplement
(Credit: Garna Zarina/Shutterstock)


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Vitamin B12 is an essential nutrient that plays an indispensable role in keeping the body healthy.

Most people get enough B12 from animal-based foods in their diets without issue. Certain lifestyle factors or medical conditions, however, can cause vitamin B12 deficiency, resulting in serious health problems.

For many B12-deficient individuals, adding extra B12 to the diet with supplements or fortified foods can easily correct the problem. But how much do you actually need and how does it impact your body?

The Role of B12 in the Body

Our bodies naturally store B12, although just how much varies from person to person.

“We all have a certain amount of B12 stored – every infant is born with a certain amount of B12 derived from maternal sources,” says Ralph Green, a pathologist at University of California, Davis.

After we’re born, B12 from our diet that we don’t use goes to restock our B12 stores. These internal reserves can last for a year or more, providing a safety net against potential deficiencies.

The reason why our bodies need B12 is that it’s critical for nervous system development and function. Specifically, B12 maintains the health of nerve cells and ensures the efficient transmission of signals throughout the body.

How Much B12 Per Day?

According to experts, we should have a daily intake of 2.4 micrograms (mcg) of vitamin B12 for anyone over 14. Pregnant and lactating women should slightly increase their daily intake to support fetal and infant health. And without enough B12 to support the nervous system, people can experience numbness or tingling in the limbs and difficulty with coordination.

"If a B12 deficient state continues for too long or is very severe,” says Green, “it can do irreversible damage to the nervous system.”

B12 is also a key player in DNA synthesis, contributing to cell division, growth and repair.

When the body lacks B12, fast-replicating cells are first to suffer. This shortage can particularly impact the production of healthy red blood cells, which carry oxygen throughout the body. Without B12, red blood cells can become enlarged, resulting in fatigue and weakness.

Read More: Dietary Supplements Are No Substitute for a Healthy Lifestyle

What Causes Vitamin B12 Deficiency?

Anyone can have a B12 deficiency, but people with certain health complications or dietary restrictions can be more at risk than others.

Lack of animal or dairy products

People who limit or eliminate animal products from their diets can be at risk for B12 deficiency. Among vegans and vegetarians, infants, children, teens and pregnant and breastfeeding women are most vulnerable.

Not enough stomach acid

Stomach acid helps release vitamin B12 from the food we eat. Some older people or those who take certain medications might have less stomach acid, making it harder to get enough B12.

Digestive disorders or surgeries

Some stomach or small intestine surgeries can affect how our body absorbs vitamin B12. Similarly, disorders of the digestive tract like Crohn's and celiac disease can also cause problems absorbing B12.


Some medications, like metformin for type 2 diabetes, can interfere with B12 absorption. Drugs that reduce stomach acid, like proton-pump inhibitors and histamine blockers, may also lower B12 levels.

Underlying medical conditions

In some individuals, certain medical conditions can hinder the body's ability to absorb B12. For these people, taking B12 supplements may not be effective, and they may require other medical interventions.

For those with dietary changes, without impaired B12 absorption, incorporating B12 with supplements and fortified foods should generally suffice to meet their B12 needs.

In the case of medical conditions, it is essential to seek guidance from a licensed medical professional who can assess the specific situation and recommend the most effective form of vitamin B12 supplementation.

B12 Consumption

When naturally occurring in food, B12 is bound to proteins. For our bodies to absorb it, B12 must be separated from these proteins during the digestion process.

In contrast, B12 in supplements and fortified foods is in its "free form," which makes it easier for the body to absorb.

Because B12 is a water-soluble vitamin, any excess not needed by the body is excreted through urine. And, according to the Institute of Medicine, “no adverse effects have been associated with excess vitamin B12 intake from food and supplements in healthy individuals.”

Misinformation About B12 and Supplements

As with most supplements, there is no shortage of misinformation surrounding B12 supplements.

According to the National Institutes of Health (NIH), B12 supplements in all forms – capsules, sublingual tablets, nasal sprays and more – are all equally effective in meeting the body’s B12 needs.

Taking more B12 than your body requires does not pose any harm, nor does it provide any remarkable health benefits – what your body can’t use will just end up down the toilet.

Read More: What You Should Know About Magnesium Supplements

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