Some signs of vitamin B-12 deficiency include tiredness, lightheadedness, weakness and rapid breathing or fast heartbeat, notes WebMD. Constipation, diarrhea, upset stomach, weight loss and sore tongue are additional symptoms. Some others include bleeding gums, pale skin and easy bruising and bleeding.
Vitamin B-12 deficiency is caused by a number of different conditions, advises WebMD. Some of them include pernicious anemia, which is an absorption disorder that makes it difficult for the body to absorb vitamin B-12, and atrophic gastritis, which is a disorder characterized by the thinning of the stomach lining. Heavy drinking, long-term acid-reducing drug use and immune system disorders such as lupus and Graves' disease also result in vitamin B-12 deficiency. Conditions that affect the small intestine, including parasites, growth of bacteria, celiac disease and Crohn's disease, can also result in lowered B-12 and B-12 deficiency. Weight loss surgery or other surgeries that require removal of part of the small intestine or stomach are additional causes.
Vegan or vegetarian diets can result in a deficiency in B-12 if the vegetarian or vegan does not consume an adequate amount of dietary B-12, notes WebMD. Pregnant vegetarian women may give birth to babies who are deficient in vitamin B-12.