Anemia is a condition characterized by an inadequacy in the number of red blood cells that are healthy. That is, the amount of healthy red blood cells present in the body is low. Vitamin B 12 deficiency anemia is caused by pernicious anemia. Vitamin B 12 which is obtained from consuming foods such as eggs, meat, shellfish, and poultry is needed by the body to make red blood cells. Pernicious anemia is caused by the inability of a person to produce a special protein substance called intrinsic factor (IF) which is tasked with binding vitamin B12 so that absorption can be done in the intestines. The stomach cells release this protein. Therefore, when the stomach is unable to produce enough intrinsic factors, the intestine is unable to absorb vitamin B12 properly. Vitamin B12 is an important nutrient that assists in the production and functioning of red blood cells in the body.
Pernicious anemia is not a popular condition as according to a study in the journal of blood medicine in 2012, pernicious anemia is prevalent in 0.9 percent  of people older than 60 and 0.1 percent of the population generally. However, about 50% of adults  with anemia from a deficiency of vitamin B12 are caused by pernicious anemia. Pernicious anemia has the word ‘pernicious’ in it because it was once taken as a very deadly and dangerous disease due to the unavailability of treatment options. Today, however, with vitamin B12 injections and in some cases oral supplementation, the disease is quite easy to treat. Although, if the disease is not treated in due time, a deficiency of vitamin B12 can result in serious complications.
Pernicious anemia progresses slowly, so it may be hard to recognize or make a diagnosis, because you may have gotten used to feeling unwell. However, common symptoms include: