What causes a vitamin B12 deficiency, and what are the symptoms?

Vitamin B12 deficiency occurs when a lack of vitamin B12 or folate causes the body to produce abnormally large red blood cells that cannot function properly. Low Vitamin B12 can sometimes be caused by following a vegan diet or a long-term poor diet. Some of the symptoms of vitamin B12 deficiency are lack of energy, muscle weakness, depression, pins and needles and problems with memory. If you believe you have b12 deficiencies, please contact a medical professional for supplementing advise.