Your body uses vitamin B12 to make DNA and nerve and blood cells. Most people get an adequate supply of the vitamin from the foods they eat. Vitamin B12 deficiencies are not common, because the body stores the excess supply, according to MedlinePlus. But people who have a potassium deficiency are at risk of a vitamin B12 deficiency if they are prescribed potassium supplements. Vitamin B12 deficiency causes a condition called pernicious anemia, also called megaloblastic anemia. A vitamin B12 deficiency can be treated with injections of the vitamin.
Fatigue
As with other types of anemia, people with pernicious anemia often develop fatigue, according the MedlinePlus. Some people with a vitamin B12 deficiency may also experience bouts of lightheadedness or feel drained. These symptoms often develop even though the person is getting adequate sleep and rest.
Tingling and Numbness
Pernicious anemia can also cause a person to experience tingling and sensations of numbness, according to the National Institutes of Health Office of Dietary Supplements. Most often, these sensations are first noticeable in the feet and hands, although other parts of the body can be affected as well.
Depression
Some people with vitamin B12 deficiencies can develop depression or may experience other behavior and mood changes. Other symptoms include irritability and lack of focus. Memory can also be impaired, or dementia may develop.
Bowel Habits
When a vitamin B12 deficiency causes pernicious anemia, you may notice a change in your bowel habits, according to MedlinePlus. Constipation and diarrhea both are signs of a B12 deficiency, although these are common medical symptoms and do not necessarily indicate pernicious anemia.
Shortness of Breath
In some cases, people with pernicious anemia experience shortness of breath. This most often develops with exertion or during exercise.
Balance Problems
A vitamin B12 deficiency affects your neurological system, and as levels drop, you may notice that your balance is affected. Neurological changes such as loss of balance often indicate a vitamin B12 deficiency that has been progressing for an extended period.
Loss of Appetite
Pernicious anemia can cause a loss of appetite. But loss of appetite can also be a sign of many other health conditions, including other types of anemia. If you experience a noticeable decrease in appetite, visit your doctor.
Mouth Soreness
A vitamin B12 deficiency can cause soreness throughout the mouth and tongue. Other oral symptoms include red, swollen or bleeding gums.
