February 28

B12 Deficiency: Symptoms & How To Fix It

Medically review by Kim Langdon

B12 Deficiency

Let's talk about B12! You likely associate this vitamin with energy as it's often added to caffeinated beverages and energy drinks for a boost.

For vegetarians and vegans, the emphasis is even higher on B12, and you've likely heard non-meat eaters are at higher risk of deficiency.

There's more to it than just that, though, and it's not only the herbivores who are at risk.

In fact, it's probably much more common than it is diagnosed.

Like with all vitamins, each one has a unique and important role in the body. Vitamin B12 is needed to form new red blood cells, nerves, and DNA - it's a creator of sorts.

It's other main function is prevention of anemia which you'll learn more about in the signs and symptoms of deficiency.

vitamin b12 deficiency

First, it's important to differentiate B12 from other vitamins. The body doesn’t make B12 which means we need to consume it.

The best source of B12 we can take in often comes from animal foods, but bread and cereals are often fortified with it which can be another good source - particularly for elderly people.

Another important thing to consider is that the body doesn’t store vitamin B12 for long, so consumption should be consistent and often to keep levels healthy.

Deficiency does not simply come down to how much of that nutrient you take in via diet; it comes down to how well you absorb it (directly related to gut health), demand of the nutrient due to physiological factors, genetics that impact utilization, and more which we will discuss further in the next section.

Deficiency is much more common in the elderly population, so individuals over the age of 65 should regularly getting serum levels tested.

Finally, B12 deficiency is closely linked to two other important factors: folate and homocysteine. B12 functions a lot like like folate (vitamin B9).

If a folic acid supplement is taken, it can mask - but not address - vitamin B12 deficiency.

It's also worth noting that people with low folate levels also tend to have low B12 levels, and higher homocysteine levels (3). B12 is required to convert homocysteine back into thiamine (vitamin B1).

Signs & symptoms of B12 deficiency

symptoms of B12 deficiency

In this section, we want to cover both symptoms of deficiency and some key factors that make individuals more susceptible to developing B12 deficiency.

It's important to address both ends of the spectrum for treatment and preventative measures, especially because deficiency tends to be asymptomatic; for example, B12 deficiency won’t cause anemia until Stage 4.

Earlier signs include weakness, tingling in the hands and feet, balance problems, irregular/rapid heartbeat, confusion, weakness, or sudden loss of appetite.

  • Deficiency is a common cause of macrocytic and pernicious anemia - the latter being an autoimmune disorder - and has been linked to neuropsychiatric disorders (1).
  • Patients with depression tend to have low folate levels (associated with B12/homocysteine) (3).
  • People with immune system disorders are more likely to have B12 deficiency.
  • Thinning of the stomach lining or atrophic gastritis makes individuals more prone to B12 deficiency due to reduction in absorption.
  • Low blood levels of folate and vitamin B12, and elevated homocysteine levels are associated with Alzheimer’s (2).

Homocysteine is an amino acid that results during the breakdown of protein in the body. When found in high concentrations, it's been linked to an increased risk of heart attack and stroke.

Elevated homocysteine levels are thought to contribute to plaque formation by damaging arterial walls.

Like we mentioned above, it's not just vitamin B12 we need, and many of these symptoms are thought to be linked to a host of deficiency or in homocysteine's case - overload.

B12 deficiency is also strongly linked to neurological disorders and brain/nerve damage (personality changes, dementia, MS, Parkinson’s, general, cognitive decline).

It's also associated with learning disabilities in children and infertility. B12 virtually affects every tissue in the body, so there's a reason we stress its importance. 

Addressing B12 deficiency

Addressing B12 deficiency

If you believe you might be deficient or you are someone whose physiological conditions make it more likely that you'll develop a deficiency, what's your next step?

Good question! Sometimes, supplementation just isn't enough. Besides, finding out if you're actually in need of a boost can be tough enough.

The serum B12 test doctors most often use doesn’t pick up everyone with deficiency because it only measures the B12 in the blood. We need to pick up more sensitive markers to detect it earlier.

Even so, getting a test is very simple and can give you an idea of where your blood levels of vitamin B12 stand.

If you feel as though you are truly at risk of deficiency and subject to serious health issues because of it, we recommend more sensitive testing such as a methylmalonic acid or MMA test.

Over 50% of vegans are deficient, and 7% of vegetarians (based on serum B12 testing). Sensitive markers detect deficiency at earlier stages with 83% of vegans being deficient and 63% of vegetarians being deficient.

This indicates the need for accurate testing, and also how high-risk non-meat eaters are for deficiency. All plant-based eaters should be supplementing with B12.

Now, let's discuss preexisting conditions that impact B12 levels. Treating or fixing H. pylori infection - a bacterium found in the stomach and duodenum- can increase B12 absorption, fix deficiency and treat anemia (5). 

People with digestive issues, leaky gut and conditions that affect the small intestine such as Crohn’s, celiac disease, bacterial growth, and parasites are more likely to be deficient in vitamin B12.

This leads us to believe that treating leaky gut will significantly increase our body's ability to absorb B12 and prevent deficiency.

Intestinal permeability is a good marker of how well we absorb all nutrients, so if you're struggling with gut issues or autoimmunity, getting enough B12 is crucial.

Studies show that supplementation with oral vitamin B12 is a safe and effective treatment for addressing deficiency states (1).

If you're not taking in a lot of animal foods or fortified grains, vitamin B12 has good bioavailability. Like with any vitamin or mineral, whole food sources are the best and easiest for our bodies to use.

B12 is found in meat and dairy products; the best animal sources are liver and kidney, but you can also get it in any animal foods such as fish (especially sardines), meat, poultry, eggs, milk, and milk products.

A great plant food source of B12 is nutritional yeast. No matter the source, it's good to remember that only tiny amounts of vitamin B12 can be absorbed at once (4).

This reinforces the notion that B12 intake should be consistent.

How much vitamin B12 do you need?

How much vitamin B12 do you need?

Like with many deficiencies and illnesses, there must be an emphasis on infants and the elderly - especially since B12 deficiency can cause long-term damage.

This means that infants might suffer the effects later, and the elderly may be suffering the effects on top of dealing with other conditions either caused by or exacerbated by B12 deficiency.

Infants who suffered from deficiency were more at-risk for anorexia, irritability, and overall failure to thrive later in life (6). Infants up to age 6 months should receive 0.4 mcg per day. 

Babies age 7-12 months should get around 0.5 mcg, and children age 1-3 years: 0.9 mcg.

Daily dose recommendations:

  • Kids age 4-8 years: 1.2 mcg
  • Children age 9-13 years: 1.8 mcg
  • Teens age 14-18: 2.4 mcg 
  • Adults: 2.4 mcg (2.6-2.8 mcg if pregnant or breastfeeding)

The major takeaway is this: B12 deficiency is very common, even if your serum levels look normal! The long-term effects of B12 deficiency are absolutely detrimental, so eat those superfoods like sardines and liver on a regular basis.

We hope you learned something new today here, and if you liked it, make sure to share it!

This article was fact checked for accuracy by Dr. Kim Langdon, MD. As always, this is not personal medical advice and we recommend that you talk with your doctor.


1. R, Oh, and Brown DL. “Vitamin B12 Deficiency.” American Family Physician, 1 Mar. 2003, europepmc.org/abstract/med/12643357.

2. Clarke, MD Robert. “Folate, Vitamin B12, and Serum Total Homocysteine Levels in Confirmed Alzheimer Disease.” Archives of Neurology, American Medical Association, 1 Nov. 1998, jamanetwork.com/journals/jamaneurology/fullarticle/774437.

3. Fava, Maurizio. “Folate, Vitamin B12, and Homocysteine in Major Depressive Disorder.” The American Journal of Psychiatry, Mar. 1997, pp. 426–428., search.proquest.com/openview/787d67703afd0957e3b33cb70e644efe/1?pq-origsite=gscholar&cbl=40661.

4. Schjønsby, H. “Vitamin B12 Absorption and Malabsorption.” Gut., Dec. 1989, pp. 1686–1691., www.ncbi.nlm.nih.gov/pmc/articles/PMC1434458/?page=1.

5. Kaptan, MD Kür?ad. “Helicobacter Pylori-Is It a Novel Causative Agent in Vitamin B12 Deficiency?” Archives of Internal Medicine, American Medical Association, 8 May 2000, jamanetwork.com/journals/jamainternalmedicine/fullarticle/485312.

6. Graham, Stephen M. “Long-Term Neurologic Consequences of Nutritional Vitamin B12 Deficiency in Infants.” The Journal of Pediatrics, vol. 121, no. 5, Nov. 1992, pp. 710–714., doi:https://doi.org/10.1016/S0022-3476(05)81897-9.


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