B-12 Deficiency Symptoms: Everything You Need to Know

by Dr. Edward Group DC, NP, DACBN, DCBCN, DABFM Published on , Last Updated on

A tired individual. Fatigue and low energy are one of few signs of Vitamin B-12 deficiency symptoms.Vitamin B-12, also known as cobalamin, is an essential nutrient in the B-complex of the eight B water-soluble vitamins. This nutrient must be consumed through animal foods [1 (although supplementation may be more ideal) to ensure adequate intake. Vitamin B-12 is structurally the largest and most complex of all the vitamins that have been discovered, and a surge of research is coming to the forefront displaying its awesome power in human health.

Role of Vitamin B-12

Vitamin B-12 is integral to normal, healthy energy metabolism in all cells of the body, as well as amino acid and fatty acid metabolism. B-12 is also extremely important in a myriad of other vital physiological processes such as brain function, nervous system health, production of the myelin sheath (nerve insulation), red blood cell formation, bone marrow health, and DNA synthesis/regulation.

A unique nutrient, vitamin B-12 isn’t produced by plants, animals, or even fungi. Instead, this essential vitamin is produced only by certain bacteria. Human requirements for vitamin B-12, as set by the Daily Recommended Intake (DRI) are 2-3 micrograms/mcg (microgram is one millionth of one gram) per day, [2 upwards of 4-7 micrograms/mcg per day in lieu of recent research.

Unfortunately, research demonstrates that intrinsic factor only allows upwards of 1.5 mcg of B-12 absorption per feeding. Keep this in mind when planning your daily meals, and consider quality B-12 supplementation on a daily basis to ensure adequate intake. There is no upper limit on Vitamin B-12 and even extremely high doses of B-12 have been shown to be safe with virtually no side effects.

What Constitutes Deficiency?

Vitamin B-12 is used by the body from the food and/or supplements we intake daily. In a healthy adult, the body can store up to 3 to 5 years worth of vitamin B-12 (a minuscule two to five milligrams in total), in large part because of the efficient use and recycling of B-12 by the liver.

Over 50% of total body reserves are stored in the liver. [3 This is one of the main reasons why a B-12 deficiency doesn’t show up until years after poor intake. Common blood testing ranges for vitamin B-12 is measured in ng/L (nanograms per liter of blood) and can be ordered by general physicians or online via specialty mail-order test companies. Vitamin B-12 blood range values include: [4]

180-914 ng/L Normal high/low range
450+ ng/L Healthy/Optimal
180-400 ng/L Conditionally low levels
150-180 ng/L Low levels where disease symptoms start

Be aware that in older adults levels between 200 and 500 pg /mL may also produce symptoms of vitamin B-12 deficiency. [4]

Blood testing for B-12 is a very important step everyone should consider doing to be certain that their levels are sufficient for optimal health as well as healthy brain/nervous system function. Though more medical doctors are becoming aware of B-12’s importance and are beginning to test their patients for this crucial vitamin, it’s not something that is widely practiced–yet. Depending on test results and possible symptoms, other simple follow-up blood tests which indirectly test for B-12 status may be suggested, including homocysteine and methylmalonic acid/MMA. [5]

Deficiency Stages

Researchers have discovered that B-12 deficiency generally occurs in four distinct stages:

Stage 1

Declining blood levels and cell stores.

Stage 2

Low cellular levels.

Stage 3

Functional B-12 imbalance characterized by increased blood level of homocysteine/MMA and a decreased rate of DNA synthesis.

Stage 4

Clinical signs/symptoms of B-12 deficiency like macrocytic anemia, peripheral neuropathy, and neurological disorders may present themselves. Some researchers suggest that diseases attributed to “old age,” such as cognitive decline, loss of mobility and balance, and memory loss, are sometimes synonymous with vitamin B-12 deficiency. In the case of neurological symptoms, cumulative damage due to long-standing deficiency may be irreversible. This impresses the importance of early diagnosis and ensuring adequate blood levels.

Causes of Vitamin B-12 Deficiency

Knowing some of the primary causes of B-12 deficiency can help inform us on how to best prevent or avoid deficiencies. A few are:

Inadequate Dietary Intake

Vitamin B-12 can only be consumed through animal foods and supplements. Children also are at high risk due to inadequate dietary consumption and lower bodily reserves, despite higher requirements per food calorie. Gastritis, stomach abnormalities/surgeries, or hereditary traits may be to blame for
impaired absorption.

Absent or Low Stomach Hydrochloric Acid

Sufficient HCl is essential, independent of intrinsic factor secretion, for cleaving B-12 from carrier proteins in food. This is thought to be a major cause of deficiency in the elderly, who generally suffer from low stomach acid.

Other causes include:

  • Celiac disease leading to small intestine damage causing impaired absorption of vitamin B-12, which is principally absorbed in the ileum.
  • Bad bacteria overgrowth in the small intestine, which some research shows can cause malabsorption of B-12.
  • Diabetes medication Metformin may interfere with absorption of B-12.
  • Parasitic infection, such as Giardiasis, can cause leaching of the vitamin leading to deficiency.
  • Genetic factors such as deficiency in the MTHFR gene, transcobalamin (another type of B-12), etc.
  • Excessive alcohol intake. [6]

Symptoms of Vitamin B-12 Deficiency

Knowing some of the common symptoms, mild and severe, of B-12 deficiency can help inform us on how to best prevent or avoid deficiencies. Since it can take years to manifest a clinical deficiency as measured by blood testing, it’s important to note that signs of deficiency can remain silent for some time as bodily B-12 levels are slowly depleted. A few are:

  • Pernicious anemia, specifically megaloblastic anemia, which is a second type of anemia that causes dysfunction of the bone marrow’s ability to manufacture red blood cells.
  • Neurological impairments such as depression, confusion, disorientation, schizophrenia, ADHD. [7] [8]
  • Memory loss, Alzheimer’s, Parkinson’s, brain fog, cognitive decline, brain shrinkage.
  • Increased fatigue.
  • Peripheral neuropathy.
  • Sexual dysfunction including low libido, low sperm count, ED, low sex hormone levels.
  • Paresthesia (tingling sensation in hands, feet, limbs).
  • Spinal cord/myelin sheath degeneration.
  • Insomnia.
  • Bowel/urinary incontinence.
  • Itchy skin. [9]

One Final Thought

Vitamin B-12 is an incredibly important and integral essential nutrient in human health, especially all manner of neurological health and red blood cell formation. When deficiencies occur in other nutrients, symptoms or disease processes can be reversed with repletion. Vitamin B-12 is so vital and important in brain and nervous system function, that often the damage from deficiency is permanent and irreversible. Daily supplementation that ensures optimal vitamin B-12 intake that far exceeds the minuscule daily requirements as set by the government and scientific health bodies is ideal.

GHC youtube Video

Watch an In-Depth Video on
Everything You Need to Know About Vitamin B-12

Video Length: 60 minutes
References (9)
  1. "Vitamin B12: MedlinePlus Medical Encyclopedia." 2006. 12 Feb. 2016
  2. "Vitamin B12 (Cobalamin) | University of Maryland Medical Center" 2013. 12 Feb. 2016
  3. National Institutes of Health. Vitamin B12. NIH Fact Sheet.
  4. "Vitamin B12 level: MedlinePlus Medical Encyclopedia." 2006. 12 Feb. 2016
  5. Mayo Clinic Medical Labs. Vitamin B12 Testing. Mayo Clinic Fact Sheet.
  6. Laufer EM, Hartman TJ, Baer DJ, et al. Effects of moderate alcohol consumption on folate and vitamin B(12) status in postmenopausal women. Eur J Clin Nutr. 2004 Nov;58*11): 1518-24.
  7. Black, Maureen M. "Effects of vitamin B12 and folate deficiency on brain development in children." Food and nutrition bulletin 29.2 suppl1 (2008): S126-S131.
  8. "Anemia - B12 deficiency: MedlinePlus Medical Encyclopedia." 2006. 12 Feb. 2016
  9. Patrick J. Skerrett. Vitamin B12 Deficiency Can Be Sneaky, Harmful. Harvard Medical School.

†Results may vary. Information and statements made are for education purposes and are not intended to replace the advice of your doctor. Global Healing Center does not dispense medical advice, prescribe, or diagnose illness. The views and nutritional advice expressed by Global Healing Center are not intended to be a substitute for conventional medical service. If you have a severe medical condition or health concern, see your physician.

  • Rebecca

    Your first sentence is incorrect… Vitamin B12 is also known as COBALAMIN…. the cyanocobalamin is a very cheap synthetic version that most of the population should avoid.

    Methylcobalamin is the methyl form of B12.

    However there are two other, BETTER forms.

    Hydroxycobalamin and adenosylcobalamin are the preferred forms for many people with specific genetic mutations, including VDR and COMT.

    Whenever I see a product with cyanocobalamin in it, I refuse to buy it. It just tells me it is worthless crap.

  • Carlos Alvarez

    Excellent topic with a lot of details. As the article states, B12 is essential for the nervous system and bone marrow. I assume is also affects the health of your joints and ones?

  • Charlotte Parker

    For those struggling with B12 deficiency, I recently heard about a new oral prescription alternative to the injections called Eligen B12. Has anyone heard of it? I recently read that it works even if you don’t have intrinsic factor (so even if you don’t have normal gut absorption). Apparently it came out a month or two ago

  • marcovth

    Serum B12 is measured in pg/ml or pmol/L. If your B12 level is under 450 pg/ml AND you have B12 deficiency, you are in a grey zone of in between 200 and 450 where you have to be treated. As soon as you start to experience neurological symptoms you have to be treated because within 6 months to 1 year they might become permanent. In my opinion, screw all the official ranges, if you have about half of the B12 deficiency symptoms, and you level is below 450 pg/ml, you need treatment. BTW, when babies are born, the average level is around 2000. Around age 50 the average level is around 1000. For 70 years+, the levels can easily get lower than 500, meaning deficiency can easily develop. If you are 50 yo and your level is 250, something is clearly not right, you would expect that level 20 years later, but not at age 50. If you can understand this, than for sure a doctor should too.

  • Nicki Thorn

    Transcobalamin is the transporter across into the cells, not ‘another type of B12’ …… I discovered Transcobalamin issues when I had my genetics done.

  • julie

    I’ve just been diagnosed with a level of 134 and have memory problems , depression , aniexty , numbness in lips , pain all over , severe tiredness. I put it down being a diabetic , had viral meningitis last year , have a 1 year old and 7 year old. I just plod on because I have to. Find it difficult to get to sleep at nights.

  • marcovth

    With a level of 134 (pg/ml or pmol/L?) it starts to become dangerous. Anything below 50 pg/ml will become critical. Please see you doctor very soon and ask for B12 injections. If the doctors doesn’t want to give that, I would simply start to take one 5000 mcg Methyl-B12 sublingual(!) melting pill per day that you keep in your mouth for 5-10 minutes. This for a couple of months and then 1000 mcg when you start to feel better. But with your level to start with injections would be better. However, if you don’t get them, start with pills right away, you can buy them at the pharmacy or online as a supplement. Also, do not take B9 (Folate/”FolicAcid”) at this point, the B12 level is too low, and B9 will only make it lower. Your doctor should know about this interaction. If not, find another doctor. Also, the lower the B12 is the more painful it will be to recover when your body finally receives enough new B12. You have to bite through this period, don’t give up ! The pains can increase for a while (2 or 3 months), but when your body gets used to the higher level of B12, the symptoms should get much less after that. At that point you can also check if B9 (methyl-Folate) makes you feel even better besides the B12. I was almost crippled last summer, and the symptoms are now gone for 90%. Please buy the book “Could it be B12?”, and please note that I am patient and not a doctor, always consult a doctor for medical advise.

  • marcovth

    Another note: make sure a close family member studies B12 deficiency with you, and ask that family member to come when you visit your doctor. You are sick, you feel really bad, and you don’t have the energy to fight with a doctor who is not well informed. The best chance for treatment is when you bring some one who can argue for you, and who can help to find another doctor when unsuccessful.

  • Tonya

    Thank you very much for the post. I’m actually studying as a health practitioner and have been battling with neuropathy from a spinal injury. Its really sad but the most of my doctors would like to see me that or they just do not understand or want to focus on the effects of vitamin and mineral deficiencies. This has fueled my need for education and the reason to advocate for my own health. My blood serum test was 460 and immediately my doctor told me I was normal and great. Now to find out that it would actually require A spectracell test I realize it could be completely off. I really appreciate this information and it has saved me hours of study.

  • Ethel

    Dear Dr. , I have just watched your video. I found it very interesting and knowledgeable. Here is a quick overview of my situation. I have just been diagnosed with B-12 deficiency. The lab report revealed a count of 30. This was all brought on due to a stomach problem about two months ago. I had an Ultrasound done and it revealed sludge in my Gallbladder and I am meeting with a surgeon in about a week. I also have a diagnosis of severe depression and anxiety. Diagnosed years ago and on medications for this. Just wanted you to know that your information was very helpful and I will continue to research my situation. Also, I have started B-12 Injection. Thanks so much for your information.

  • Kyra

    Nicki Thorn did you have grey hair at an early age? I think I may have it genetically, because my sister got two tests done for her and my nephew from 23andme and it said they have the mutation. I found on Google that b12 deficiency causes grey hair, and am worried I have to have the injections? I tried a liquid b12 complex from the nutrition store and it didn’t get rid of my grey hair. My sister said something about that it wouldn’t work because I don’t metabolize it properly. Do you metabolize it properly??

  • Wales

    Rebecca, what brand of hydroxy &/or adenosylcobalamin do you use?

  • Sarah Tucker

    Has anyone ever gotten migraines from B12 it seems when I try and take them I get a migraine I suffer from them and take magnesium to help but I have a low B-12 and have never been able to take a supplement because it makes headaches worse… I have never tried this supplement though .. Thank you!

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  • Sheila

    How do you get B12 after having a bowel resection and no longer have a terminal ileum?


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