Vitamin B-12 is an essential vitamin most commonly found in meat, dairy products and shellfish. Vitamin B-12 helps maintain healthy red blood cells and nerve function and is necessary for DNA production, the genetic material in all cells. The American Academy of Family Physicians explains that as many as 15 percent of adults over the age of 65 may suffer from a B-12 deficiency. B-12 deficiencies can lead to a decrease in red blood cells known as B-12 deficiency, or macrocytic or pernicious, anemia which can cause numerous symptoms.
Red blood cells contain hemoglobin and hemoglobin carries oxygen to the tissues throughout the body. When the body lacks vitamin B-12, this deficiency can affect the production of healthy red blood cells, and a lack of red blood cells means a lack of oxygen. The National Institutes of Health explains that this lack of oxygen can cause people to feel fatigue, loss of energy and lightheadedness upon standing or with exertion.
Shortness of Breath
Just as a lack of red blood cells can cause fatigue, it may also manifest as shortness of breath. People with a vitamin B-12 deficiency may begin to notice that they breathe heavy upon exertion such as walking up stairs or during exercise.
While many people naturally have fair or light complexion, a sudden diminishing in skin color can often indicate a B-12 deficiency. Generalized paleness due to illness can affect the entire body, including the nails and even the inner mucosa of the mouth and eyes. This loss of color results from the lack of red blood cells circulating in the body.
When a vitamin B-12 deficiency goes without treatment for long periods, nerve damage can occur. This nerve damage can manifest as confusion, depression, loss of balance, inability to concentrate, numbness and tingling of the hands and feet and, in extreme cases, dementia, according to the National Institutes of Health.
A B-12 deficiency can often affect the intestinal tract. People with mild anemia may notice the occasional bout of constipation or diarrhea. When B-12 anemia becomes more severe, it can lead to loss of appetite, severe constipation, diarrhea and abdominal cramping and bloating, according to the National Institutes of Health.
People with a B-12 deficiency may begin to notice unusual bleeding. The first place a person may notice blood is in the sink when brushing his teeth. Bleeding gums and a swollen red tongue can indicate B-12 deficiency anemia. Rectal bleeding or bloody stool can also indicate B-12 anemia. Women may also notice excessively heavy and menstrual periods. People experiencing unusual bleeding should alert their physician so that they can decide whether further testing is necessary.