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9 Main Symptoms of Vitamin B12 Deficiency

9 Main Symptoms of Vitamin B12 Deficiency

Symptoms of Vitamin B12 Deficiency

What is Vitamin B12?

Vitamin B12 (also called cobalamin) is a water-soluble vitamin that plays an important role in the normal formation of red blood cells and for the health of the nerve tissues. Vitamin B12 (cobalamin) is an important micronutrient that is essential for DNA synthesis and providing your cells with energy. Vitamin B12 is not generally found in foods of plant origin. but fortified cereals are an available source of vitamin B12 with high bioavailability for vegetarians. You need vitamin B12 to make red blood cells, which carry oxygen through your body. A lack of B12 can lead to anemia, which means your body does not have enough red blood cells to do the job. You may then feel weak and tired.

Causes of  Vitamin B12 Deficiency

A deficiency of vitamin B12 is more common with age, because as you age the body has great difficulty absorbing nutrients from the foods you eat.

There are several reasons for the low levels of B12 in your blood. The main reasons for a cobalamin deficiency are related to insufficient dietary absorption or a diet low in vitamin B12.

According to research published in the Journal of the Nutrition ( Oxford Academic), vitamin B 12 is a cofactor in two reactions: (1) the transition of methylmalonic acid to succinyl coenzyme A, and (2) the transition of homocysteine to methionine. Therefore, a decrease in vitamin B 12 can result in higher levels of methylmalonic acid and homocysteine.[1]

Let’s take a closer look at the main reasons why symptoms of B12 deficiency appear.

Diet as a Cause of Vitamin B12 Deficiency

One of the main reasons for having lower than normal B12 levels is a lack of vitamin B12 in the diet.

A vegetarian diet low in foods containing vitamin B12 is the most common cause of vitamin B12 deficiency. Vegetarians (who also avoid eggs and dairy products) are at very high risk of this vitamin deficiency because vegetables and fruit do not contain vitamin B12.

Researches are found that compared to non-vegetarians, vegetarians have a lower body mass index (BMI), serum cholesterol, serum glucose, and blood pressure, with a lower mortality rate from ischemic heart disease (IHD). However, underestimating good cobalamin (Cbl) supplementation can negate these benefits.[2]

Impaired Absorption Can Results in Lack of Vitamin B12

Malabsorption may be a reason to show signs of vitamin B12 deficiency even if you include meat in your diet.

Insufficient absorption of B12 can occur for several reasons. For example, low levels of vitamin B12 are sometimes seen in people who have undergone gastric bypass surgery. Bariatric patients are at increased risk of developing vitamin B12 deficiency because their digestive tract has been altered to interfere with the natural absorption of this vitamin.[3]

Lack of intrinsic factor

Another reason to remedy a vitamin B12 (cobalamin) deficiency is that you don’t have enough intrinsic factor to aid digestion.

 Intrinsic factor is a protein made in the stomach. It is needed to absorb vitamin B12. This type of B12 deficiency anemia is called pernicious anemia.

How much vitamin B-12 should you take?

According to NIH, the recommended daily allowance (RDA) for vitamin b12 in micrograms (mcg) are as follow:

 Recommended Dietary Allowances (RDAs) for Vitamin B12
  Age Male Female Pregnancy Lactation
0–6 months 0.4 mcg 0.4 mcg    
7–12 months 0.5 mcg 0.5 mcg    
1–3 years 0.9 mcg 0.9 mcg    
4–8 years 1.2 mcg 1.2 mcg    
9–13 years 1.8 mcg 1.8 mcg    
14+ years 2.4 mcg 2.4 mcg 2.6 mcg 2.8 mcg

Symptoms of Vitamin B12 (Cobalamin) Deficiency

Vitamin B12 deficiency anemia is a condition in which your body does not have enough healthy red blood cells due to a lack (deficiency) of vitamin B12. This vitamin is needed to make red blood cells, which carry oxygen to all parts of your body. Without red blood cells, your tissues and organs do not receive enough oxygen. Without enough oxygen, your body cannot function as well.

Vitamin B12 is nicknamed the energy vitamin.   If you have a vitamin B12 deficiency, you may become anemic. The symptoms of a vitamin B12 deficiency are often not very specific, so a vitamin B12 deficiency can go unnoticed for a long period of time. It is also easily confused with other conditions and therefore remains misdiagnosed.

Fortunately, a vitamin B12 deficiency is reversible if you spot the symptoms in time and take steps to remedy a vitamin B12 deficiency. Your body cannot produce vitamin B12 and you must get it from food or supplements.

In the absence of any apparent dietary intake, deficiency symptoms generally take five years or more to develop in adults, although some people experience problems within a year. A very small number of individuals with no obvious reliable source appear to avoid clinical symptoms of deficiency for twenty years or more.

Although water-soluble, vitamin B12 is stored in the liver, kidneys, and other body tissues, so a vitamin B12 deficiency can go undetected for a long time. This is where the danger lies. By the time the disease is detected, irreversible damage may already have been caused.

It is important to treat the symptoms of cobalamin deficiency as it can have serious consequences.  Read on to find out more about the role of vitamin B12 in the body, the causes and symptoms of vitamin B12 deficiency, and how to treat it.

 Weakness and  fatigue

One of the most common signs of a lack of sufficient vitamin B12 is extreme fatigue.Symptoms of Vitamin B12 Deficiency

Anemia is a condition in which you lack enough healthy red blood cells to carry adequate oxygen to your body’s tissues. Having anemia can make you feel tired and weak.

In the elderly, this type of anemia is often caused by an autoimmune disease known as pernicious anemia. People with pernicious anemia do not produce enough of an important protein called intrinsic factor.

In many cases, correcting the results of a B12 deficiency means having more energy. However, there could be other reasons why you feel tired all the time.

Heart palpitations and shortness of breath

Anemia resulting from vitamin B-12 deficiency can cause mild shortness of breath. This may be related to a lack of red blood cells and a rapid heartbeat. Anyone who is experiencing real difficulty breathing should seek medical attention immediately.

The lack of energy caused by anemia due to cobalamin deficiency will also cause shortness of breath. Researchers found that If you become anemic due to B12 deficiency, you may feel short of breath and a little dizzy, especially when you exercise. This is because your body does not have the red blood cells it needs to deliver enough oxygen to the cells in your body.

Pale or yellowish skin

People with B12 deficiency often have a pale or slightly yellowish appearance on the skin and the whites of the eyes, a condition called jaundice

A 2008 observational study showed that a patient with only skin lesions may be highly suspicious of vitamin B12 deficiency. Skin lesions that do not respond to conventional therapy could most likely be an indication of vitamin B12 deficiency. These skin manifestations respond rapidly to vitamin B12 therapy. Early treatment with vitamin B12 will prevent serious complications of vitamin B12 deficiency.[4]

Swollen Tongue

A lack of vitamin B12 can also make your tongue look inflamed, swollen and painful.

According to Standford Medicine a B12 deficiency will also make the tongue painful and bright red in colour. Glossitis, by causing swelling of the tongue, can also make the tongue appear smooth.

Cognitive Impairment

One of the neurological symptoms associated with B12 deficiency are problems related to brain function and memory.

A  2020 cross-sectional, multicentre study conducted on patients with minimal cognitive impairment (MCI) to assess vitamin B12 and homocysteine levels. All patients with vitamin B12 deficiency received replacement therapy and were re-evaluated after three months through the Mini-Mental State Examination (MMSE) and symptom review.[5]

A total of 202 patients were included in the study. The result showed that of these, 171 (84%) reported a marked improvement in symptoms after vitamin B12 replacement, while MMSE scores improved in 158 (78%) patients. Of the remaining 44 patients who reported no symptomatic improvement, MMSE scores improved in 26 patients, while 18 patients showed no improvement in MMSE scores.

Tingling in Hands and Feet

According to one 2013 study in Harvard Health publishing ( Harvard Medical School) vitamin B 12 deficiency can also cause strange sensations, numbness, or tingling in the hands, legs, or feet.

A 2012 study showed that vitamin B12 deficiency can lead to demyelination of nerves in the peripheral and central nervous system and is associated with peripheral neuropathy, loss of sensation in peripheral nerves, and lower limb weakness in the elderly. In particular, vitamin B12 deficiency is associated with neuropathy of large fibers (type A); type A nerve fibers act as both sensory and motor fibers. Thus, vitamin B12 may be associated with both sensory and motor functions of peripheral nerves. [6]

Difficulty Maintaining Balance

The neurological impact of low vitamin B12 levels can also affect your balance and gait.

A 2017 study of vitamin B12 deficiency in older adults showed that high levels of plasma homocysteine, which is metabolized to methionine and cysteine by vitamin B12, were consistently associated with slow walking speed and reduced physical activity.[7]

A deficiency of vitamin B-12 over time can lead to damage to peripheral nerves and subsequently to movement problems.

Numbness in the feet and limbs can make it difficult for a person to walk without support. It can also cause muscle weakness and decreased reflexes.

Vision Problems

If you have blurred vision for no apparent reason, you may need to correct a vitamin B12 deficiency.

An untreated vitamin B12 deficiency causes damage to the nervous system at the level of the optic nerve that leads to your eyes.[8]

The researchers found that the thickness of the nerve fiber layer in the temporal quadrant of the retina correlates with plasma vitamin B12 levels. Vitamin B12 deficiency that is not fully treated with oral folic acid supplementation can worsen neurological symptoms. Prompt diagnosis and recognition of vitamin B12 deficiency optic neuropathy are essential for visual recovery.[9]

Changes in Mood

Low levels of vitamin B12 can lead to significant mood changes such as depression and mood swings.

Vitamin B-12 and other B-group vitamins play a role in the production of brain chemicals that affect mood and other brain functions. Low levels of vitamin B-12 and other B vitamins such as vitamin B-6 and folate may be linked to depression.

If you experience the above symptoms, consult your doctor, and never ignore them.




How Long It Takes to Correct Vitamin B12 Deficiency

Recovery from a vitamin B12 deficiency takes time and you may not feel any improvement in the first few months of treatment. Improvement can be gradual and may continue for six to twelve months.

Vitamin B12 Deficiency Treatment

To prevent vitamin B12 deficiency, your body needs to absorb this vitamin during digestion. it is better that you get vitamin B12 from foods such as liver, beef, chicken, eggs, and dairy products. The normal range for vitamin B-12 in the blood is between 200 and 900 nanograms per milliliter (ng/mL).

Vitamin B12 deficiency can be treated by intramuscular injections of cyanocobalamin or by oral vitamin B12 therapy.  In general, patients with an irreversible cause should be treated indefinitely, while those with a reversible cause should be treated until the deficiency is corrected and symptoms disappear.

Dietary sources of vitamin B12

You can help prevent anemia due to vitamin B12 deficiency through proper nutrition. Unless an intrinsic factor or malabsorption has caused your cobalamin deficiency.

Sometimes, you can help to fix a vitamin B12 deficiency or prevent anemia through diet. Making sure your diet includes foods rich in vitamin B12 will help keep your levels within the normal range. Foods high in vitamin B12 include Animal liver and kidneys, clams, sardines,  tuna, fortified nutritional yeast, trout, salmon, red meat, poultry and eggs, a variety of vegetables, fruits, whole grains, fat-free or low-fat milk, and milk products. Many ready-to-eat breakfast cereals are fortified with vitamin B12.

Supplements to Treat Vitamin B12 Deficiency

Dietary supplements can help correct a B12 deficiency faster than increasing your vitamin intake.

Vitamin B12 supplements are recommended for people at risk of vitamin B12 deficiency. These include the elderly, pregnant or breastfeeding women, vegetarians and vegans, people with intestinal problems, and people who have had stomach surgery.   Vitamin B12 supplements come in many forms. You can swallow, chew, or drink them, or put them under your tongue.

Like vitamin B12 from fortified sources, vitamin B12 in supplements is synthetically manufactured, so it is suitable for vegans.

Taking B12 supplements under the guidance of your doctor can help correct a B12 deficiency quickly. Taking vitamin B12 is good if you suffer from pernicious anemia, megaloblastic anemia, or absorption problems due to an intrinsic factor. Vitamin B12 is also commonly found in many multivitamins.




Vitamin B12 injections – in case of severe cobalamin deficiency

Muscular injections are a type of vitamin B12 treatment if you suffer from a severe deficiency. In critical cases of anemia due to vitamin B12 deficiency, injections can quickly correct a B12 deficiency.

However, some studies showed that oral supplements can be just as effective as vitamin B12 injections are effective in restoring normal levels of serum cobalamin in all patients. [10]

Other studies suggest that low levels of B12 may be involved in fibromyalgia and chronic fatigue syndrome. It is possible that they are responsible for the low energy levels typical of these two conditions.

You don’t need a prescription for B12 supplements. They are available at most places that sell supplements. However, if you are considering B12 supplementation, talk to your doctor. Your doctor can give you better advice and make sure you are not doing anything dangerous. Your pharmacist is also a valuable resource regarding negative interactions between different treatments, including supplements.


[1] Tucker KL, Selhub J, Wilson PW, Rosenberg IH. Dietary intake pattern relates to plasma folate and homocysteine concentrations in the Framingham Heart StudyJ Nutr. 1996;126:3025-3031. Accessed September 9, 2009.

[2] Gianluca Rizzo, Antonio Simone Laganà, Agnese Maria Chiara Rapisarda,Gioacchina Maria Grazia La Ferrera, Massimo Buscema, Paola Rossetti, Angela Nigro, Vincenzo Muscia, Gaetano Valenti, Fabrizio Sapia, Giuseppe Sarpietro, Micol Zigarelli, and Salvatore Giovanni Vitale Vitamin B12 among Vegetarians: Status, Assessment and Supplementation , 2016 Dec; 8(12): 767. doi: 10.3390/nu8120767

, PMCID: PMC5188422

[3]Malinowski SS. Nutritional and metabolic complications of bariatric surgery [review]Am J Med Sci. 2006;331:219-225.

[4] Rajendran Kannan, Cutaneous lesions and vitamin B12 deficiency An often-forgotten link,  2008 Apr; 54(4): 529–532.PMCID: PMC2294086

PMID: 18413300

[5]Shazia Jatoi, Abdul Hafeez, Syeda Urooj Riaz, Aijaz Ali, Muhammad Ishaq Ghauri, Maham Zehra Low Vitamin B12 Levels: An Underestimated Cause Of Minimal Cognitive Impairment And Dementia, Published: February 13, 2020 DOI: 10.7759/cureus.6976

[6] Kira Leishear,  Robert M. Boudreau,  Stephanie A. Studenski,  Luigi Ferrucci, Caterina Rosano,    Nathalie de Rekeneire, Denise K. Houston, Stephen B. Kritchevsky, Ann V. Schwartz, Aaron I. Vinik, , Eva Hogervorst, Kristine Yaffe, , Tamara B. Harris, , Anne B. Newman, , Elsa S. StrotmeyerMPH, The Relationship of Vitamin B12 and Sensory and Motor Peripheral Nerve Function in Older Adults,  2012 Jun; 60(6): 1057–1063. doi: 10.1111/j.1532-5415.2012.03998.x ,PMCID: PMC3376015, NIHMSID: NIHMS364098 , PMID: 22690982


[8]Dissanayake Mudiyanselage Priyantha Udaya Kumara Ralapanawa , Kushalee Poornima Jayawickreme ,, Ekanayake Mudiyanselage Madhushanka Ekanayake , Widana Arachchilage Thilak Ananda Jayalath  B12 deficiency with neurological manifestations in the absence of anemia,  2015 Sep, DOI: 10.1186/s13104-015-1437-9.

[9] Amber R. Scharnweber, OD, FAAO, ABCMO, and Richard J. Zimbalist, OD, FAAO

Vitamin B12 Deficiency Optic Neuropathy: a Teaching Case Report,  Optometric Education Volume 42 Number 3 ( Summer 2017)

[10] M Cristina Castelli , Kristen Friedman, James Sherry, Karen Brazzillo, Lise Genoble, Prateek Bhargava, M Gary I Riley Comparing the efficacy and tolerability of a new daily oral vitamin B12 formulation and intermittent intramuscular vitamin B12 in normalizing low cobalamin levels: a randomized, open-label, parallel-group study PMID: 21600388, DOI: 10.1016/j.clinthera.2011.03.003



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