Vitamin B12 Deficiency Impacts More Than Just Energy

Dr. Jolene BrightenPublished: Last Reviewed: Wellbeing Leave a Comment

Vitamin B12 is a vital nutrient for energy, brain health, hormone function and pregnancy. Which is why a vitamin B12 deficiency impacts more than just energy. Here are some of the other equally serious vitamin b12 deficiency symptoms.

Deficiency is Common

Depending on which study you look at, anywhere from 20-40% of the U.S. population has suboptimal levels of this nutrient. And these numbers are based on traditional lab values, not optimal functional values!

Twenty-40% may not sound so bad, but what if I told you that vitamin B12 deficiency can have profound effects on your energy and cognitive health?

B12 in the Body

Vitamin B12 is an essential nutrient for brain and heart function. Both of which, of course, lend themselves to overall health and vitality.

B12 works together with folate to aid in red blood cell formation and DNA synthesis.

It also helps to lower levels of the amino acid homocysteine, which, at elevated levels, is linked to serious conditions such as heart disease, osteoporosis, depression, and dementia.

This means that vitamin B12 deficiency symptoms include depression and other mood disorders, brain fog, fatigue, muscle weakness, lack of coordination, and hair loss. Worse – chronic depletion of B12 could mimic the signs and symptoms of brain diseases like dementia.

Vitamin B12 in Preconception and Pregnancy

For my prenatal ladies, lack of adequate B12 can also lead to neural tube defects, like spina bifida.

While folate is most commonly taken to prevent this, in the absence of B12, the folate cannot be effectively metabolized and utilized by the body. The neural tube defect is estimated to occur between the 3rd and 4th week after conception, which is too early for most women to notice they are pregnant.

For this reason, I recommend both folate and B12 supplementation as part of a complete prenatal 3 months prior to conception. If you’re a woman and there is a chance you could become pregnant (even a slight one), I recommend at least having a complete B12 complex as part of your daily routine.    

Vitamin B12 Deficiency Symptoms

  • Paleness
  • Headaches
  • Tongue soreness
  • Loss of appetite
  • Fatigue
  • Anemia
  • Numbness/ tingling of hands and/or feet
  • Memory loss
  • Disorientation/ Dementia
  • Low blood pressure
  • Intermittent constipation or diarrhea

How B12 deficiencies occur

There are several reasons you might be deficient in vitamin B12. Here are just a few:

You’re vegan or vegetarian

The most common reason for B12 deficiency is a vegan or vegetarian diet. B12 occurs naturally in animals and animal-derived products, so you may experience a deficiency if you avoid these foods.

Approximately 50% of vegetarians and 80% of vegans are deficient in B12. It is a common misconception that you can easily get B12 from non-animal sources. Plant-based sources that claim to have adequate B12 actually have forms of B12 that block your B12 and increase the demand!

You have low HCl levels

While the word “acid’ doesn’t necessarily conjure thoughts about health and vitality, hydrochloric acid, or HCl, is vital to your body’s absorption of vitamin B12.

HCl is produced in the stomach to help you break down your food so it can be absorbed in the small intestine. As you age, your production of HCl naturally declines, but there are other causes for decreased production of HCl. Poor dietary practices, over the counter and prescription medications and autoimmune conditions like Hashimoto’s, Crohn’s and celiac disease can also inhibit HCl production and absorption of B12.

Your gut needs help

If there are other digestive issues at play, like SIBO (small intestinal bacterial overgrowth), leaky gut (or intestinal permeability), or other signs of gut dysbiosis, it’s possible you’re simply not absorbing the nutrients from your food.

Gut health is vital to B12 absorption. If you suspect any of these conditions, talk to your doctor about treatment options.

You don’t have to have a disease to have poor gut health! It is important to evaluate your digestion as a contributing factor to B12 deficiency. You need stomach acid to liberate B12, intrinsic factor to ready it for absorption and a healthy small intestine to absorb it.

Your intrinsic factor isn’t doing its job

Intrinsic factor is a protein that is excreted from the parietal cells in the stomach. Its primary function is to enable your body to absorb B12.

Pernicious anemia, atrophic gastritis, or antibodies that are directly attacking your intrinsic factor can all keep you from being able to absorb B12.

You’re over 50

Aging is a risk factor to developing a B12 deficiency — most likely due to the function of the gut.

Some studies show that up to 20% of Americans 65 and older are deficient in B12. Starting B12 supplementation at 50 years old can prevent you from developing a deficiency and all the symptoms and conditions that go along with it.

Your medication is interfering


Certain prescription and over the counter medications can inhibit your ability to absorb, utilize or maintain a healthy B12 level. Proton Pump Inhibitors (PPI) and other acid-blocking drugs can decrease the amount of B12 available to you in your food.

Common cholesterol, gout, and diabetes drugs are known to inhibit absorption. Talk to your doctor about B12 testing if you are taking any of these medications.


You have an autoimmune condition

Atrophic gastritis, pernicious anemia, Crohn's disease, and celiac disease all affect your ability to liberate B12 from your food and absorb it.

If you have a family history of autoimmune disease or have an autoimmune disease, you should speak with your doctor about having proper testing to determine if this is the cause of your B12 deficiency.

You are hypothyroid

Hypothyroidism is a condition in which you have too little thyroid hormone. Thyroid hormone is necessary for stomach acid production and gut health. Read more about the connection between hypothyroidism and low stomach acid in the link.

How to test for B12 deficiency

A good Naturopathic or Functional Medicine Doctor will be able to tell you whether or not you should start supplementation based on your symptoms and medical history. Blood tests are available, but are not always 100% accurate, so if you or your doctor suspect a deficiency, it’s best to begin supplementation.

If you and your doctor do decide to test, vitamin B12 concentrations and serum methylmalonic acid levels can be tested to help determine the severity and root cause of your deficiency. I also recommend testing folate, homocysteine and checking for a common gene mutation, MTHFR.

Investigate Your Red Blood Cells

A simple CBC can also tell you the size of your red blood cells. A large red blood cell, which can be revealed by an elevated MCV (mean corpuscular volume) is a sign of poor B12 status or utilization. An elevated MCV may also be due to folate and B6 deficiency. In my practice, I begin supplementation any time the MCV is 92 or higher.

If you are supplementing and continue to show signs of deficiency, ask your doctor to test you for a condition known as pernicious anemia. It is an autoimmune disease which makes it impossible to absorb B12 via the gut.

How to get a B12 reboot

Vitamin B12 can be stored in the liver of a healthy person for up to 5 years and is synthesized in the small intestine, so it may take a while for a deficiency to present. Please note: a healthy person.

If you suspect that you have absorption issues or you’re not getting adequate amounts of B12 from dietary sources, you might want to consider supplementation.

In fact, if you suffer from any of the following symptoms, you may want to consider B12 supplementation:

  • Fatigue, anemia
  • Frequent colds, flus
  • Thyroid and adrenal imbalances
  • Anxiety, depression, insomnia
  • PMS, menopause, acne
  • Allergies, herpes, psoriasis
  • Nerve pain, dementia, brain fog
  • Obesity, heart disease and many more…

B12 in Your Diet

The best way to get optimum levels of B12 is directly from your food. B vitamins work synergistically with each other and other nutrients to give your body exactly what it needs to function optimally, so when in doubt, eat real whole foods.

Foods high in B12 and other B vitamins include meat, poultry, organ meat, high-quality dairy products (great if you’re not sensitive to these), trout, herring, mackerel, and egg yolk. Please note that it’s not possible to correct true B12 deficiencies with food alone.

What about plant sources of B12? Nutritional yeast and seaweed are high in B12, but there’s some evidence that non-animal products may offer a type of B12 that isn’t as active in the body, so I wouldn’t rely on these sources. In addition, the form of B12 from seaweed may actually block B12 utilization by the body!

How to supplement:

Pill or capsule form

When purchasing a B12 supplement, it’s important to look for the active form of the vitamin. Methycobalamin is the active form of the nutrient and if preferred over cyanocobalamin. In fact, all B vitamins should be taken in their activated methylated forms.

Remember, B vitamins work together, so it is often best to take a B complex. When supplementing a single B vitamin alone, it is possible to create additional needs for other B vitamins in the body. This is because replenishing one B vitamin can increase metabolic processes that increase the demands for other B vitamins.

I recommend my B-Active Plus for my patients because it has an array of B vitamins and additional co-factors that help you utilize the B vitamins.

B Complex with Active B Vitamins

 fight vitamin b12 deficiency symptoms

Sublingual B12

Sublingual B12 allows you to absorb the vitamin directly into your bloodstream, bypassing the gut, without an injection.

This is generally recommended when there is an issue with gut absorption — SIBO, leaky gut, low stomach acid, atrophic gastritis, etc. Or it may be recommended if you’ve been taking a B complex for an extended period of time without results.

Of course, you can always safely opt for the sublingual form of B12 to give your brain and body a boost.

I generally recommend a sublingual B12. One losenge daily can help you increase your energy, boost your mood, and support healthy detox (which makes for some awesome hormonal health).

B12 injection

Injecting B12 directly into the bloodstream is an efficient option when treating B12 deficiency or addressing ongoing issues with fatigue, depression or decreased cognitive function. Shots are injected directly into the muscle (usually the glutes or upper arm) and are quick and relatively painless.

Treatment plans may vary from one injection per month to several over a span of weeks, depending on the condition. Generally, injections are 1,000 mcg of B12 per session.

You don’t have to have a chronic B12 deficiency to warrant a B12 shot; sometimes they’re prescribed as energy boosters for athletes or those who suffer from adrenal fatigue.

Taking care of you

I work with all of my patients to determine the most effective way for supplementation. We want to ensure optimal intake and absorption of targeted nutrients. Do you think you might be deficient in B12? Would you like to talk to a qualified practitioner about supplementation or dietary changes for vibrant health, visit our scheduling page.

If you are struggling with low energy, brain fog, decreased exercise tolerance, depression or anxiety, please download a free copy of my Hormone eBook to learn more about how nutrition and hormones may be impacting your health.

If you're a new mom and struggling with energy, please check out my book Healing Your Body Naturally After Childbirth. In it, I share a lot of energy boosting information that has helped many of my patients.

Do you have hypothyroidism? If so, I'd highly recommend my good friend, Izabella Wentz's book, Hashimoto's Thyroiditis Root Cause.

Looking for a food-based solution to anxiety? Check out the Anti-Anxiety Food Solution by my dear friend Trudy Scott.

Struggling with autoimmune disease? Please read The Autoimmune Fix by my friend Dr. Tom O'Brien.

Have you tried Vitamin B12 or a B complex? What benefits have you seen? Share below in the comment. 

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About The Author

Dr. Jolene Brighten

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Dr. Jolene Brighten, NMD, is a women’s hormone expert and prominent leader in women’s medicine. As a licensed naturopathic physician who is board certified in naturopathic endocrinology, she takes an integrative approach in her clinical practice. A fierce patient advocate and completely dedicated to uncovering the root cause of hormonal imbalances, Dr. Brighten empowers women worldwide to take control of their health and their hormones. She is the best selling author of Beyond the Pill and Healing Your Body Naturally After Childbirth. Dr. Brighten is an international speaker, clinical educator, medical advisor within the tech community, and considered a leading authority on women’s health. She is a member of the MindBodyGreen Collective and a faculty member for the American Academy of Anti Aging Medicine. Her work has been featured in the New York Post, Forbes, Cosmopolitan, Huffington Post, Bustle, The Guardian, Sports Illustrated, Elle, and ABC News. Read more about me here.