Pernicious anemia is a chronic autoimmune disease that prevents the absorption of vitamin B12 due to the stomach's impaired ability to produce a protein called intrinsic factor (IF). Intrinsic factor is vital for the absorption of vitamin B12 in the intestines. Insufficient intrinsic factor production leads to the body not being able to obtain enough vitamin B12. Anemia, or blood deficiency, is a condition characterized by a decrease in the number of red blood cells in the blood. Red blood cells contain hemoglobin, which is responsible for transporting oxygen. A deficiency of red blood cells causes serious disruptions in the body's ability to deliver oxygen and nutrients to tissues. Pernicious anemia is a specific type of this general anemia, particularly stemming from vitamin B12 deficiency. Although vitamin B12 is a water-soluble vitamin, it is largely stored by the body. Due to this storage capacity, vitamin B12 deficiency and thus symptoms of pernicious anemia usually appear within 3 to 5 years. However, once B12 levels drop, it can take a long time to return to normal levels, and this situation increases the risk of pernicious anemia.