Vitamin B12 is a water-soluble vitamin that keeps your nerves and red blood cells healthy. It is responsible for the smooth functioning of several critical body processes. It is possible for the body to develop a vitamin B12 deficiency. This deficiency is usually reported with symptoms of fatigue.Country Life Vitamin B-12 1 Mcg, 60-Count formulated in a special base to release its nutrients over a prolonged period of time.