How is Vitamin-B12 Related to Anemia?

Anemia is when the red blood cells in the body are either not functioning correctly or when their numbers are not sufficient in the circulatory system. Types of anemia associated with vitamin B-12 are pernicious anemia, macrocytic anemia, and megaloblastic anemia. Pernicious anemia can cause vitamin B-12 deficiency, which can then lead to megaloblastic anemia and macrocytic anemia.

Pernicious Anemia

Your body receives Vitamin B-12 through meat and dairy products. It is involved in maintaining the structural integrity of DNA, preserving myelin sheath around neurons, and  has critical role in the metabolism of folate, another major vitamin needed in the body. With vitamin-B12 being such an essential vitamin in the body, it is vital that we get an adequate daily intake. Any cause of decreased intake or absorption of this vitamin can have serious repercussions. As this vitamin in mainly found in animal-based products, vegetarians and vegans are often at a risk of deficiency and may need supplements.


Pernicious anemia arises from an autoimmune reaction where the body’s immune system attacks the parietal cells of the stomach. These cells secrete a glycoprotein called intrinsic factor into the stomach cavity, which is needed to absorb vitamin B12 in the diet. Without this factor, vitamin B12 is excreted out of the body. Pernicious anemia causes vitamin-B12 deficiency, with 20% of people aged over 60 in the USA and UK having B12 deficiency.


The human body generally has large stores of vitamin-B12 and the symptoms of pernicious anemia can take years to arise. Weakness, lack of coordination, and numbness or tingling can be some of the first symptoms, and are a result of the lack of vitamins rather than the anemia itself. When the deficiency becomes severe, symptoms can worsen into paraplegia, serious weakness, incontinence, and spasticity. Also, all the normal symptoms of anemia, such as cardiac arrhythmia, fatigue and pale skin will be present.


The treatment for this condition is to replace all the lost vitamin-B12 in the body through regular injections, and to resolve any underlying cause of the condition. This treatment normally completely reverses any symptoms, unless serious nerve damage has occurred which irreversible.

Macrocytic and Megaloblastic Anemia

When the body is deficient in vitamin B-12. it can produce red blood cells that are abnormally large, called macrocytes, which do not function properly. The main cause of macrocytic anemia is called megaloblastic anemia, which is due to reduction in DNA synthesis. When red blood cells are not functioning properly, the hemoglobin cannot bind to oxygen efficiently. Thus, many tissues around the body are not provided with enough oxygen to upkeep with their normal metabolism. This is called hypoxia and can lead to cell death. Deficiency in vitamin B-12 can also impair DNA synthesis, but the synthesis of RNA continues to happen without being converted into DNA. This causes lot of build-up of genetic material within the red blood cells, leading to abnormal size and lack of function.

Further Reading

Last Updated: Oct 14, 2018

Written by

Jack Davis

Jack is a freelance scientific writer with research experience in molecular biology, genetics, human anatomy and physiology, and advanced analytical chemistry. He is also highly knowledgeable about DNA technology, drug analysis, human disease, and biotechnology.


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