Vitamin B12 Deficiency – Everything You Need To Know

By: Catherine Payne

Image by: @laviperchik

Vitamin B12 is a key vitamin for personal health and well-being.  It is one of the 30 essential nutrients required on a regular basis. Intake leads to the development of healthy blood cells, brain cells, and body tissues. Deficiencies can be overlooked because there are eight B vitamins to balance, many with similar symptoms that relate to functioning blood cell absorption, gut health, energy levels, and cognition. Since it is not produced by the human body, Vitamin B12 is a dietary must. It is not in plant foods, only animal products. Because of this B12 is often included in multivitamins, especially custom vitamins for vegetarians, vegans, and women over 40 though many others may need it as well. Utilizing a personalized vitamins approach will ensure deficient levels are covered leading to improved organ system function, increased cognitive health and an overall healthy individual.

The U.S. Department of Health and Human Services found that vitamin B12 deficiency represents up to 15% of the public. In fact, prior to and during pregnancy, a mother’s diet is a significant determinant for B12 levels for their growing baby, so the NIH recommends vitamin B12 as a critical component of prenatal vitamins. From conception throughout the lifespan, vitamin B12 is a daily essential nutrient.

What Are B Vitamins?

B vitamins function on the cellular level. They are the keys that unlocks hundreds of enzymes and allow them to do their job.  Without each of them the locks stay closed.  

You may have heard of B6 and B12, and likely B9 by its more common name- folate, but all 8 B vitamins play a role in overall health, each with their own function. If you read the ingredient list on some food products (fortified) and vitamin bottles, you’ll likely see some of the B complex nutrients. The B vitamin complex include:

  • B1     (thiamin)
  • B2     (riboflavin)
  • B3     (niacin)
  • B5     (pantothenic acid)
  • B6     (pyridoxine)
  • B7     (biotin)
  • B9     (folate)
  • B12   (cobalamine)

Research from the Harvard School of Public Health suggests that this complex initiates a cascade of actions that lead to macronutrient metabolism, blood cell creation, oxygen transport throughout the body, brain cell regeneration, maintenance of healthy skin, improved mood and increased energy. The Bs are water soluble vitamins, so you do not store them in the body. In order to sustain appropriate metabolism, daily continual intake is necessary.

Food Sources of B Vitamins

  • Meats
  • Fish
  • dairy products
  • Eggs
  • Fortified products

Everyone needs B vitamins, but they are especially important for women of childbearing age.  A custom vitamins regimen will provide the optimal variety and dosage of the B complex and lead to optimal health and wellness for mom and baby. Interestingly, after age 40, metabolic alterations necessitate increased intake through supplementation as well, due to the inability to absorb food sources of Vitamin B.  Continue reading to discover if your personalized vitamins should include Vitamin B12.

Role of Vitamin B12

The body uses Vitamin B12 for:

  • Creating new red blood cells
  • Proper DNA synthesis
  • Brain and neurological function
  • Regulating fat and protein
  • Protecting the nervous system
  • Maintaining the body’s energy level

Vitamin B12 is necessary for a healthy life.  While the body does not make Vitamin B12, it is commonly found in animal-products like meat, eggs and dairy products. Vitamin B12 -and all the Bs in the complex- are bound to protein in food products. Bioavailability is adequate for those with appropriate metabolism. 

Surprisingly, an inability to breakdown and absorb Vitamin B is more common than physicians originally thought.  For those who avoid intake of animal products or those with metabolic issues, Vitamin B is readily available and absorbed through supplementation. A custom vitamins approach can be a successful strategy for those individuals who lack adequate amounts of Vitamin B12. Personalized vitamins pick up where the diet leaves off, giving the needed nutrients to create a healthy life. What personalized vitamins do you need? Start by taking our quick quiz or asking your doctor.

Prenatal Vitamins: Vitamin B12

Prenatal vitamins are important for all women who are trying to get pregnant, pregnant or breastfeeding, according to the NIH, and help support a healthy diet. The pregnancy journey is beautiful and joyful, but deciding which vitamin is best is often a stressful decision, especially for new moms. The health of their growing baby is top priority. The spectrum of critical nutrients during pregnancy is wide, and the B complex plays a large role for mom and baby. Vitamin B12 is essential for neural tube formation, brain and spine development, production of red blood cells, and production of nerve cells for the growing baby and helps mom through improved metabolism, increased energy and mood, reduces stress, and maintains normal neurological function. Research has shown that when moms take Vitamin B12 during and for a few weeks after delivery, cognitive development for the child increases significantly.

Mothers should be intentional about maintaining adequate levels of Vitamin B12 before, during and after pregnancy.  Vegan and vegetarian diets promote healthy and provide most nutrients for themselves and their growing baby.  However, due to the lack of B12 in nearly all plant sources, those who are vegan or vegetarian should be monitoring B12 intake closely and taking prenatal vitamins throughout.

Dosage in Pregnancy

The Recommended Daily Intake during pregnancy is 2.6 mcg. Breastfeeding mothers require 2.8 mcg  and infants require 0.4- 0.5 mcg, according to the NIH.

Do I have a B12 Deficiency?

Vitamin B12 deficiency comes from a lack of nutrient rich foods or the body’s inability to absorb vitamin B12. It’s a sneaky and harmful deficiency, but difficult to detect. As people age, their bodies have a harder time absorbing B12. Vegans and vegetarians are at a high-risk of a deficiency due to the lack of typical proteins in their diet. Intestinal and stomach diseases are also factors that can lead to vitamin B12 deficiency.  Those at a high-risk will typically be:

  • Anemic
  • Reduced stomach acidity
  • Intestinal disorders
  • Intestinal surgeries
  • Vegetarians and vegans
  • Pregnant or lactating women and their infants
  • Older adults

Symptoms of a Vitamin B12 Deficiency 

Vitamin B12 is crucial to an energetic, lucid, and healthy life. Deficiency will lead to negative side effects that are sometimes hard to detect and avoidable with customized vitamins that combat deficiency. While these symptoms are not solely correlated with a Vitamin B12 deficiency- which is why pinpointing a B12 deficiency is sometimes hard.  Simply measuring B12 in the blood is not an adequate way to test for deficiency.  You can still have normal levels in circulating blood, while still having a deficiency. Better indicators of deficiency are methylmalonic acid and homocysteine.  These are subclinical biomarkers which rise in response to inadequate levels of B12.  If you suspect a Vitamin B12 deficiency, be your own advocate with your physician and make sure they are measuring these indicators.

Knowing what leads to deficiency can help understand the best mode of treatment and prevention.  There are several key factors that lead to a B12 deficiency.

  • Avoiding animal products
  • Inadequate intrinsic factor
  • Decreased stomach acid
  • Intestinal surgeries

Common symptoms 

  • Anemia (megloblastic and pernicious)
  • Tired, weakness, lightheadedness
  • Tingling of hands and feet, numbness
  • Fever and sweating
  • Pale skin and/or sore tongue
  • Breathlessness
  • Constipation
  • Loss of appetite
  • Weight loss
  • Mental problems like depression, confusion, and memory loss

Food Sources of B12

Since Vitamin B12 is not produced by the body, one’s diet is the dominating factor in Vitamin B12 levels. Animal products are the primary source for adequate B12 intake. Vegans and vegetarians will experience greater difficulty obtaining adequate levels of the vitamin.  It is possible for those who eat a plant-based diet to consume adequate doses of the B complex, but it must be intentional. Listed are foods to help specialized diets get their needed dosage of Vitamin B12: 


  • Yogurt
  • Low-fat milk
  • Cheese
  • Eggs
  • Cereals with added levels of Vitamin B12
  • Nutritional yeast


  • Non-dairy milk
  • Meat substitutes
  • Cereals with added levels of Vitamin B12
  • Nutritional yeast

Fun Fact

Plant-based fan girls take note:

Nori, the dried purple seaweed used to make sushi, may be one of the only plant sources of B12.  

However, the amount of B12 in it varies greatly, so it is not considered to be a source for nutrient density purposes.

And if you eat fish: salmon rolls will be a double hitter

Getting familiar with a food label and being intentional about dosage of Vitamin B12 consistently is the best way to ensure adequate intake through diet. Many cereals and non-dairy dairy products are fortified with Vitamin B12, but double check to be sure! For those who choose a plant-based diet- and don’t get us wrong, we are advocates of plant-based- it can prove difficult to reach adequate intake of B complex.  

Research has shown that the bioavailability of B12 through supplementation is actually higher than through food (85% compared to about 50%).  This is most likely due to the chemical structure and binding of the nutrient to fiber within the food source. During pregnancy and states of deficiency, this consideration is especially important. Custom vitamins can help ensure the gaps are filled and the necessary dosage is just the right amount- not too high and not too low. Most people are fine with vitamin intake through a pill (or some prefer liquid).  In a certain percentage of the population however, it is necessary to administer B12 shots into muscle tissue when inadequate intrinsic factor is an issue. A physician can determine if that is necessary through appropriate testing.

Prevention: Vitamin B12 Deficiency

Dr. Martin Kohlmeier, MD, PhD is the editor-in-chief of BMJ Nutrition, Prevention, and Health. He argues that “nutrition is a hard science…If somebody wants to know which foods are good sources of vitamin B12 and how it gets from ingested food into the bloodstream, we can be confident that the answer today will be the same as 50 years from now.” He continues, “It is easy enough to prevent vitamin B12 deficiency with food supplementation for people at risk.”  Preventing a Vitamin B12 deficiency is not difficult; diet and supplements are two easy ways to get the needed amount of Vitamin B12.

When it comes to vitamin B12, augmenting the diet with vitamin intake to fill the gaps is a simple way to round out overall health. B12 supplements come in many forms: capsules, teas, liquid drops and sprays. Knowing how to navigate supplement intake is key. It is possible to take a dose that is too high, though for water soluble vitamins toxicity is rare. The NIH recommends to stay below the indicated Upper Limit. In fact, it isn’t necessary to have extremely high intake in most cases. The most reasonable approach for most people is to use vitamins in lower doses within the RDA to fill gaps missed by the diet. A custom vitamins plan can help you navigate vitamin B12 needs to optimize health and wellness. Most prenatal vitamins will include B12, but not all meet the requirements. Navigating this with a health coach will help give you peace of mind.  Unless your doctor indicates you need high intakes, staying within the recommended allowance is a safe and effective strategy.

Vitamin B12 Dosage

The RDA for women is 2.4 mcg per day, according to the NIH. Stick to the recommended dose until specified by your doctor.

Dietary Reference Intakes (DRIs) recommendations for vitamin B12 are developed by the Food and Nutrition Board (FNB) at the Institute of Medicine (IOM) of the National Academies (formerly National Academy of Sciences).

Check out our quick quiz to get a match tailored for you

or contact us at to chat with a health coach to personalize your vitamins.

Check out our minibooks on insta for more


Tell us all the things you want more of and we’ll deliver


Download eatclean30

Enter your email to receive eatclean30 and the latest news and updates from 

Vitamin and Me. 

You have Successfully Subscribed!