side effect of vitamin B12

Side effect of vitamin B12


So, here we discuss about side effect and benefits of vitamin B12. To begin with, vitamin B12 is water-soluble. It exists in many different ways. It is present in many foods, available as supplements, and also exists as medicines and also contains the mineral cobalt.

Other forms of vitamin B12 are Methylcobalamin and 5-dexyadenosylcobalamin found in the human metabolism process. We need it for red blood cell formation, DNA synthesis, and as well as for neurological functioning in our body.

Deficiency of vitamin B12 

  • Tiredness
  • Lack of energy
  • Paraesthesia
  • Sore and red tongue
  • Mouth ulcers
  • Muscle weakness
  • Disturbed vision
  • Psychological problems

Intakes of Vitamin B12

The intake of vitamin B12 varies from age and gender.  People having problems in absorbing vitamin B12 from foods they must consume vitamin B12-fortified foods, or take oral vitamin B12 supplements or vitamin B12 injections.  Those who consume supplements of vitamin B12 or intake fortified cereal 4 times per week are more likely to suffer from vitamin B12 deficiency.

Moreover, a higher level of folate can cause vitamin B12 deficiency and aggravate anemia. It can also worsen the symptoms linked with vitamin B12 deficiency. If vitamin B12 is not treated then it can lead to damage to the nervous system permanently. Folic acid intake must not exceed 1000 mg in healthy adults daily.

Sources of Vitamin B12


Vitamin B12 is found in animal products like fish, meat, beef, pork, ham, poultry, lamb, and fish, egg especially haddock and tuna, dairy products such as milk, cheese, and yogurt and also in some nutritional yeast products.  It is not present in plant foods.  Vitamin B12 is fortified in soya milk and breakfast cereals.  A variety of vegetables, fruits, whole grains, fat-free, low-fat milk, and oils are good sources of vitamin B12.


Vitamin B12 is present as cyanocobalamin in dietary supplements.  Cyanocobalamin is a form that the body converts it to methylcobalamin and 5-deoxyadenosylcobalamin. Dietary supplements contain methylcobalamin.  Approximately doses 10 mcg of a 500 mcg oral supplement is absorbed in healthy people. Vitamin B12 is available in tablets.


Vitamin B12 which is in the form of cyanocobalamin and hydroxocobalamin can be used as medication by intramuscular injection. We use parenteral administration to treat vitamin B12 deficiency which occurs by pernicious anemia.  Vitamin B12 is used as a prescription medication in a nasal gel spray formulation.

Groups at Risk of Vitamin B12 Deficiency

The following groups are the most likely to be at risk of vitamin B12 deficiency:

Older adults

Atrophic gastritis affects older adults. It decreases the secretion of hydrochloric acid found in the stomach. Due to this, the body cannot absorb natural vitamin B12. Older adults suffering from atrophic gastric have problems in absorbing the natural vitamin B12. But however, they mostly can absorb synthetic vitamin B12 like supplements.

People with pernicious anemia

Pernicious anemia affects older adults. Older adults normally indicate a lack of intrinsic factor. Those who suffer from pernicious anemia cannot absorb vitamin B12 in their gastrointestinal tract. Pernicious anemia can be treated with intramuscular vitamin B12. A high dose of oral intake of Vitamin B12 can treat pernicious anemia.


Strict vegetarians and vegans are can have a deficiency of vitamin B12 as they consume only vegetarian natural foods. Vegetarian natural foods limited amount of vitamin B12.  Only Cereals and fortified yeasts are the only sources of plant base vitamin B12. 

Pregnant and lactating women who follow strict vegetarian diets

Furthermore, vitamin B12 is found in breast milk. Women who don’t consume animal products have a limited amount of vitamin B12 thus leading to vitamin B12 deficiency and their babies too can have a limited amount of vitamin B12. An infant born with vitamin B12 deficiency must be treated otherwise this can damage their neurological system permanently.  Therefore, these women must consume supplements of vitamin B12.


Vitamin B-12 is important in the proper functioning of the brain and our nervous system. It helps in the formation of red blood cells and helps in the creation of DNA. Vitamin B12 plays an essential part in synthesizing fatty acid and producing energy by helping in the absorption of folic acid.  

Surprising Ways Vitamin B12 Benefits Your Entire Body

Increase red blood cell formation and prevents anemia

Our body needs vitamin B12 so as to produce red blood cells. When the level of vitamin B12 is low thus is leads to anemia. Normally, a healthy red blood cell is small and round. When you lack vitamin B12 then it changes shape and becomes larger and oval thus it is cannot move freely through the bloodstream.  When blood cannot transport oxygen in the body you feel weak or tired.

 Improve heart health

Vitamin B12 plays an important role in preserving the health of the cardiovascular system. When the level of amino acid increases thus it increases the chance of getting heart diseases. Normally, amino acid builds up in the blood. It damages the arterial walls of the heart. This occurs because of a lack of vitamin B12 in the body. Heart disease can be prevented by consuming vitamin B6 and as well as folic acid.    

Improve eye health

Vitamin B12 is important for the nervous system. Adding vitamin B12 in your meal you can improve optic nerves that are connected to the nervous system.   A deficiency of vitamin B12 can damage nerves around the eyes thus leading to poor eyesight.

Support bone health and fights osteoporosis 

Vitamin B12 is important to keep the bones in good health. Lack of vitamin B12 can lead to weaker bones. When someone bones have low mineral density then the person suffers from fragile and is vulnerable to break.  It can lead to osteoporosis. In order to keep the bones fit and healthy then it is important to take a sufficient amount of vitamin B12.

Prevent birth defects

It is very important to consume vitamin B12 during pregnancy.  The mother needs vitamin B12 for the proper development of the fetus’ brain and nervous system.

A lack of vitamin B12 especially during the early stage of pregnancy increases the risk of getting birth defects.  Pregnant women can risk getting miscarriage or premature birth. Therefore, they must take an adequate amount of vitamin B12.

Boost memory and brain

A lack of vitamin B12 can lead to memory loss especially for older people. Vitamin B12 prevents brain atrophy possibly occurs when neurons are lost from the brain which causes dementia and memory loss.  Consuming foods rich in vitamin B12 helps in slowing down mental decline and manage symptoms of dementia. 

Promote gut health

A lack of vitamin B12 leads to diarrhea, constipation, and as well as the loss of appetite. It is important to consume lots of fiber and drink lots of water. Due to a lack of vitamin B12, one can suffer from Crohn disease.

Keeps hair, skin, and nails healthy

We need vitamin B12 for the production of cells in our bodies. The body needs it to nurture healthy hair, skin, and nails. The deficiency of vitamin B12 can cause various conditions affecting the skin. It has an influence on the hair and nails. One can suffer from diseases like vitiligo, hyperpigmentation, and nail discoloration.

A side effect of Vitamin B12 & Disadvantages

Drug Interactions

Most doctors do consider vitamin B12 to be safer. According to the University of Maryland Medical Center vitamin, B12 can interact with medications like Glucophage for diabetes, chemotherapy for cancer, anticonvulsants and as well as stomach acid decrease the absorption of vitamin B12.

In fact, it can lead to vitamin B12 deficiencies although you are taking 2.4 mcg daily especially for adults.  If you are taking all these medications so it is important to talk about the intake of vitamin B12 with your doctor. 

Decreased Absorption in Elderly

In order to be absorbed properly vitamin B12 requires a digestive system that is healthy and has stomach acid. As we aged and grow older so the absorption level of vitamin B12 decreases.  Thus the person suffers from a deficiency of vitamin B12. The symptoms may include anemia and as well as fatigue. Therefore, it is important for aged people to check their level of vitamin B12.

Pernicious Anemia

Particular requires a section in the stomach which is known as intrinsic factor.  The intrinsic factor is made by the cells in the stomach and allows the absorption of vitamins. One suffers from pernicious anemia due to a lack of vitamin B12.

Without this, you can get weakness, weight, loss and as well as numbness in fingers because it gives rise to healthy and fit red blood cell which carry oxygen and nutrients in our body.  Additionally, the symptom of pernicious anemia comprises memory loss, confusion, and as well as loss in balance.


As a matter of fact, research has suggested that consuming vitamin B 12 in the form of cyanocobalamin with folate and Vitamin B6 plus docosahexaenoic acid (DHA) does not reduce the risk of having cancer in older people.

But some researchers also suggest that consuming vitamin B12 and folic acid daily for 2 years can increase the chance of getting cancer, especially in older people.

Injectable vitamin B12

Injectable vitamin B12 can cause the following side effects:

  • mild diarrhea
  • itching
  • skin rash
  • headache
  • dizziness
  • nausea
  • vomiting
  • pulmonary edema and congestive heart failure early in treatment
  • vein thrombosis
  • sensation of swelling
  • polycythemia vera (rare, slow-growing blood cancer)

In all honesty, vitamin B12 may cause serious allergies reactions like swelling of face, tongue, throat, and as well as difficulty in breathing and swallowing. If you get these allergies then after taking vitamin B12 then you need to consult your doctor immediately.

If you are pregnant or doing breastfeeding then it is safe to consume vitamin B12 but in recommended dosages.


For most people, vitamin B12 is safe when one consumes it orally or applied to the skin or takes through the nose, injected in the vein, and as well as administered as a shot. But still here are some precautions which must be taken: 

Pregnancy and breast-feeding

Those who are pregnant or doing breastfeeding must be careful in exceeding the recommended dose by your doctor. 

Post-surgical stent placement

In this stage vitamin B6, B12 and folate must be avoided as they can narrow blood vessels and cause complications.

Allergy or sensitivity to cobalt or cobalamin; Leber’s disease or a hereditary eye disease

Those suffering from the above must not consume vitamin B12.

Abnormal red blood cells (megaloblastic anemia)

This can be treated with vitamin B12 but however, so it can make worsen the condition. It is important to ask your doctor for advice.

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