Do You Really Need Vitamin B12? How to Tell If Your Deficient

Vitamin B12, also known as cobalamin, is a water-soluble vitamin essential for maintaining normal function of the nervous system.

Vitamin B12 works with Vitamin B9 (folate) to produce red blood cells and help iron create hemoglobin,

the oxygen-carrying protein.

It also works with folate to produce S-adenosylmethionine (SAMe),

a compound involved in immune function and mood.

What is Vitamin B12?

Vitamin B12 also helps create our body’s genetic material, DNA and RNA.

Because it is water-soluble,

Vitamin B12 is not easily stored in the body, so it needs to be regularly consumed.

Recommended Daily Values of Vitamin B12

The amount of Vitamin B12 that you need depends on your lifestyle, age, and other factors.

The recommended dietary allowance (RDA) for Vitamin B12 is listed below:


  • Newborns to 6 months: 0.4 mcg (adequate intake)
  • Infants 6 months to 1 year: 0.5 mcg (adequate intake)
  • Children 1 to 3 years: 0.9 mcg (RDA)
  • Children 4 to 8 years: 1.2 mcg (RDA)
  • Children 9 to 13 years: 1.8 mcg (RDA)
  • Teens 14 to 18 years: 2.4 mcg (RDA)


  • 19 years and older: 2.4 mcg (RDA)
  • Pregnant women: 2.6 mcg (RDA)
  • Breastfeeding women: 2.8 mcg (RDA)

Some older adults (10-30%) may not be able to absorb Vitamin B12 from food efficiently.

Adults over the age of 50 may need to meet their daily requirement through foods fortified with Vitamin B12 or through a supplement.

What are the Symptoms of Vitamin B12 Deficiency?

As with any nutrient, deficiency in Vitamin B12 can cause health problems.

Vitamin B12 deficiency can cause macrocytic anemia and elevated homocysteine.

High levels of homocysteine have been associated with heart disease,

hough it isn’t clear whether homocysteine causes heart disease or whether it simply serves as an indication that someone may have heart disease.

Vitamin B12 deficiency is also associated with neuropsychiatric disorders,

memory loss, and other cognitive impairments.

It may even lead to mania and psychosis.

Severe deficiency of Vitamin B12 causes nerve damage and can lead to bone marrow failure.

Symptoms of Vitamin B12 deficiency include:

  1. Diarrhea
  2. Fatigue
  3. Nervousness
  4. Numbness
  5. Shortness of breath
  6. Tingling sensation in the fingers and toes

Supplementation of certain other vitamins may mask the symptoms of a Vitamin B12 deficiency.

Taking high doses of folic acid can make B12 deficiency difficult to detect.

If left untreated, Vitamin B12 deficiency can cause nerve damage.

Therefore, it is important to be aware of the different supplements you are taking and how they could be masking other problems going on within your body.

Vitamin B12 deficiency is often treated with vitamin B12 injections to bypass absorption barriers.

However, high doses of vitamin B12 in oral form have also been used effectively.

One study concluded that 2,000 mcg of oral vitamin B12 daily,

followed by a decreased daily dose of 1,000 mcg and then 1,000 mcg weekly and finally,

monthly might be as effective as intramuscular administration.

Nevertheless, overall, an individual’s ability to absorb vitamin B12 is most important when deciding what form to use vitamin B12 supplementally.   

Who is at Risk for Vitamin B12 Deficiency?

Most children and adults in the United States consume recommended amounts of vitamin B12,

according to analyses of data from the 1988–1994 National Health and Nutrition Examination Survey (NHANES III)

and the 1994–1996 Continuing Survey of Food Intakes by Individuals.

Data indicate that the median intake of vitamin B12 for the United States population is 3.4 mcg per day.

Certain situations may increase the risk of developing a deficiency in Vitamin B12. Vitamin B12 deficiency is rare among young people,

but a mild deficiency may occur depending on diet and other factors.

Since absorption through the gut declines with age,

Vitamin B12 deficiency is most likely to occur among elderly people.

Eating an unhealthy diet or having an insufficient amount of stomach acid can increase the risk of developing a deficiency.

Others at risk for Vitamin B12 deficiency include vegans and vegetarians who do not consume meat, dairy, or eggs.

This is because Vitamin B12 is found only in animal products.

People with problems absorbing nutrients due to Crohn disease, pancreatic disease,

weight loss surgery, or medications may also become deficient in Vitamin B12.

People who are infected with Helicobacter pylori or HIV have an eating disorder,

or diabetes may also be at risk for developing a deficiency in Vitamin B12.

Older adults with pernicious anemia or reduced levels of stomach acidity (hypochlorhydria or achlorhydria)

or intestinal disorders risk having a hard time absorbing vitamin B12 from both food and some oral supplements.

Because of this, vitamin B12 deficiency is quite common, affecting between 1.5% and 15% of the United States population.

Most of the time, adults are not sure of why they are deficient in vitamin B12.

While older people are still more likely to suffer from vitamin B12 deficiencies,

evidence from the Framingham Offspring Study has suggested that the prevalence of vitamin B12 deficiency in

young adults could be greater than we have previously thought.

This study found that despite their age difference, participants in three age groups (26–49 years, 50–64 years, and 65 years and older)

showed similar percentages of with deficient blood levels of vitamin B12.

Those who have a harder time absorbing vitamin B12 from foods or have low vitamin B12 diets may benefit from supplementing vitamin B12,

either through fortified foods, supplements, or injections.

The following groups are among those most likely to be vitamin B12 deficient.

  • Older adults

    • Older adults are more likely to suffer from intestinal issues like atrophic gastritis (10-30% of the United States adult population), which results in decreased absorption of vitamin B12.
  • Individuals with pernicious anemia

    • Those with pernicious anemia, a condition that affects 1%–2% of older adults, cannot properly absorb vitamin B12 in the gastrointestinal tract. Pernicious anemia is typically treated with intramuscular vitamin B12.
  • Individuals with gastrointestinal disorders

    • Those with stomach and small intestine disorders, such as celiac disease and Crohn’s disease, may be unable to absorb enough vitamin B12 from food to maintain the proper amount of body stores. Early on subtle reduced cognitive function resulting from vitamin B12 deficiency may be the only initial symptom of these intestinal disorders, followed by more serious symptoms.
  • Individuals who have had gastrointestinal surgery

    • Surgical procedures in the gastrointestinal tract commonly result in a loss of cells that secrete hydrochloric acid and an intrinsic factor which reduces the amount of vitamin B12 that the body releases and absorbs.
  • Vegetarians and Vegans

  • Vegetarians and vegans are at greater risk of developing vitamin B12 deficiency because natural food sources of vitamin B12 are limited to animal foods.

  • Pregnant and lactating women who follow strict vegetarian diets and their infants


  • Vitamin B12 crosses the placenta during pregnancy and is present in breast milk, therefore exclusively breastfed infants of women who consume no animal products may have very limited opportunities for vitamin B12 absorption. If a vitamin B12 deficiency goes undetected and untreated in infants, it can result in severe and permanent neurological damage.


Testing for Vitamin B12 Deficiency

Vitamin B12 deficiency is diagnosed based on the measurement of serum Vitamin B12 levels.

Since 50% of patients with the condition may show normal levels,

a more accurate screening method is to measure serum methylmalonic acid and homocysteine levels,

which increase early in Vitamin B12 deficiency.

Research shows that oral supplementation of Vitamin B12 is a safe and effective treatment for vitamin deficiency.

Supplementation is also useful when intrinsic factor is not present in the

stomach to aid in the absorption of Vitamin B12 (as is the case with conditions such as pernicious anemia).

Vitamin B12 in Foods

Vitamin B12 is only found in animal products, which is why studies show higher rates of deficiency among non-animal product eaters.

Fish, shellfish, dairy, organ meats, eggs, beef, and pork are all good sources of Vitamin B12.

Eating a balanced diet that includes some of these sources of Vitamin B12 can help ensure that you are getting enough of this vital nutrient.

Vitamin B12 is not commonly found in plant-based foods,

so fortified cereals are a great source of vitamin B12 for vegetarians and vegans.

Vitamin B12 can also be found in some nutritional yeast products.

It is important to note that fortified foods vary in the formula,

so it is always good to read labels to know what exactly is added.

Do I Need Vitamin B12 Supplements?

Many people are able to meet the recommended daily requirements for Vitamin B12

if they consume a diet that includes meat, fish, milk, and other dairy products. Others may need a Vitamin B12 supplement.

Vitamin B12 can be found in a variety of products including multivitamins, B-complex, and individual supplements.

Vitamin B12 is sold in oral tablets, capsules, soft gels, and lozenges,

and can also be administered through the nose via an intranasal formula.

In addition to supplementally, Vitamin B12 can be given in the form of cyanocobalamin and occasionally hydroxocobalamin

and can be administered parenterally as a prescription medication, usually by intramuscular injection.

This form tends to be used to treat vitamin B12 deficiency caused by pernicious anemia and other

conditions that result in vitamin B12 malabsorption and deficiency.

In addition to parenterally, vitamin B12 is also available as a

prescription medication in a gel formula applied intranasally.

Interested in learning whether vitamin B12 supplementation is right for you?

Take the Vitality DNA test today to find out exactly which nutrients your body needs.

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