Our bodies store 1,000 to 2,000 times more vitamin B12 than we would normally eat in a day, so the symptoms of vitamin B12 deficiency can take several years to appear.
If you have a vitamin B12 deficiency, you may feel tired or weak. These are symptoms of megaloblastic anemia, which is a hallmark of vitamin B12 deficiency. You may also have pale skin, palpitations, loss of appetite, weight loss and infertility.
Your hands and feet may numb or tingle, a sign of nerve problems. Other symptoms of vitamin B12 deficiency include balance problems, depression, confusion, dementia, poor memory and pain in the mouth or tongue.