Symptoms of untreated vitamin B-12 deficiency may include weakness, lightheadedness, tiredness, stomach upset, diarrhea and constipation. Additional symptoms may include easy bruising or bleeding, weight loss, pale skin, a sore tongue, and rapid heartbeat and breathing, states WebMD. Mild cases of vitamin B-12 deficiency often cause no symptoms.
Conditions that can lead to vitamin B-12 deficiency include pernicious anemia, which makes it difficult for the body to properly absorb vitamins; surgery that removes part of the stomach, such as weight loss surgery; and immune system disorders, such as lupus and Graves' disease, according to WebMD. Other conditions that can increase the risk of vitamin B-12 deficiency include heavy alcohol consumption, using acid-reducing drugs for extended periods of time, and conditions affecting the small intestine, such as celiac disease, Crohn's disease, a parasite or bacterial growth. Vegans and babies born to vegan mothers also have a high risk of suffering from a vitamin B-12 deficiency.
To prevent vitamin B-12 deficiency, people should eat sufficient amounts of meat, eggs, seafood, poultry and dairy products, advises WebMD. Vegetarians and patients with medical conditions that affect the body's ability to absorb vitamins should take a daily multivitamin containing vitamin B-12 and eat breakfast cereals fortified with vitamin B-12.