Vitamin B12, a member of the vitamin B complex, is an essential vitamin. Your body cannot produce essential vitamins but requires them for normal biological functioning. Typically, your body quickly releases excess B vitamins in your urine, but your liver can store vitamin B12 for years. Chronic deficiency of vitamin B12 can deplete your stores and lead to a variety of adverse effects, including nerve damage.

Functions of Vitamin B12

Your body needs vitamin B12 for the production of red blood cells, DNA synthesis and maintenance of neurological function, the Office of Dietary Supplements reports. Vitamin B12, also known as cobalamin, plays an important role in the synthesis of methionine, which your body uses in nearly 100 different physiologic processes, including the synthesis of DNA, RNA, hormones, lipids and proteins. A critical part of the production of these compounds, vitamin B12 ensures that the body has enough energy and cellular components to survive. Your body overcomes temporary deficiencies in vitamin B12 by tapping into of the liver's reserves.

Vitamin B12 and Nerve Damage

Your nervous system requires vitamin B12 for proper function and maintenance. According to the University of Maryland Medical Center, even mild deficiency can lead to signs of neurological dysfunction, such as nervousness, numbness and an abnormal tingling sensation in your extremities. Severe and chronic vitamin B12 deficiency can cause permanent nerve damage and complete loss of neurological function and sensation. Without vitamin B12 your nervous system is unable to conduct nerve impulses or sustain viable function. This inability quickly leads to nerve cell damage and deterioration. Elderly patients are often at risk for vitamin B12 deficiency owing to poor diet and a dysfunction in the digestive system. Vegans, patients suffering from malabsorptive conditions, HIV patients and people with an eating disorder are also at risk of vitamin B12 deficiency.

Vitamin B12 Requirements

To ensure that your body is receiving enough vitamin B12, the Office of Dietary Supplements has specified recommended daily allowances for the vitamin. These allowances vary depending on your age, gender and whether you are pregnant or breast-feeding. Newborns require 0.6 mcg per day, and this value slowly increases until adulthood. Adults of both genders require 2.4 mcg of vitamin B12 per day. Pregnant women require 2.6 mcg, whereas lactating mothers should consume 2.8 mcg of vitamin B12 per day

Sources of Vitamin B12

Vitamin B12 is present in many foods, particularly meat and poultry. Eating dairy products or drinking milk can also provide you with vitamin B12. Eggs and shellfish are excellent sources of the vitamin as well. In some cases, your doctor may recommend that you take vitamin B12 supplements, which are synthetically made vitamins that provide your body with adequate vitamin B12.

Vitamin B12 Overdose

Taking too much vitamin B12 can lead to an overdose and several adverse side effects. If you develop a skin rash or wheezing, consult your doctor immediately, the Mayo Clinic warns. These signs may be indications of a serious condition. Other side effects of vitamin B12 include diarrhea and mild skin irritation and itchiness.